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[PATCH v4 00/14] x86: remove paravirt_enabled

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  [PATCH v4 00/14] x86: remove paravirt_enabled "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-04-07 02:10 +0200
    [PATCH v4 06/14] x86/init: use a platform legacy quirk for ebda "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-04-07 02:10 +0200
      Re: [Xen-devel] [PATCH v4 06/14] x86/init: use a platform legacy  quirk for ebda David Vrabel <david.vrabel@citrix.com> - 2016-04-07 11:50 +0200
        Re: [Xen-devel] [PATCH v4 06/14] x86/init: use a platform legacy  quirk for ebda "Luis R. Rodriguez" <mcgrof@suse.com> - 2016-04-07 23:10 +0200
    [PATCH v4 10/14] x86/cpu/intel: remove not needed paravirt_enabled() for f00f work around "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-04-07 02:10 +0200
    [PATCH v4 14/14] x86/paravirt: remove paravirt_enabled() "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-04-07 02:10 +0200
    [PATCH v4 13/14] x86/init: rename ebda code file "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-04-07 02:10 +0200
    [PATCH v4 04/14] x86/rtc: replace paravirt rtc check with platform legacy quirk "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-04-07 02:10 +0200
      Re: [Xen-devel] [PATCH v4 04/14] x86/rtc: replace paravirt rtc check  with platform legacy quirk David Vrabel <david.vrabel@citrix.com> - 2016-04-07 11:50 +0200
        Re: [Xen-devel] [PATCH v4 04/14] x86/rtc: replace paravirt rtc check  with platform legacy quirk "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-04-14 01:10 +0200
      Re: [PATCH v4 04/14] x86/rtc: replace paravirt rtc check with  platform legacy quirk Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-04-07 15:00 +0200
        Re: [PATCH v4 04/14] x86/rtc: replace paravirt rtc check with  platform legacy quirk "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-04-08 02:40 +0200
          Re: [PATCH v4 04/14] x86/rtc: replace paravirt rtc check with  platform legacy quirk Juergen Gross <jgross@suse.com> - 2016-04-08 07:20 +0200
            Re: [PATCH v4 04/14] x86/rtc: replace paravirt rtc check with  platform legacy quirk Juergen Gross <jgross@suse.com> - 2016-04-08 08:40 +0200
              Re: [PATCH v4 04/14] x86/rtc: replace paravirt rtc check with  platform legacy quirk "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-04-08 09:00 +0200
                Re: [PATCH v4 04/14] x86/rtc: replace paravirt rtc check with  platform legacy quirk Juergen Gross <jgross@suse.com> - 2016-04-08 09:20 +0200
                  Re: [PATCH v4 04/14] x86/rtc: replace paravirt rtc check with  platform legacy quirk "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-04-08 09:40 +0200
                    Re: [PATCH v4 04/14] x86/rtc: replace paravirt rtc check with  platform legacy quirk Juergen Gross <jgross@suse.com> - 2016-04-08 10:10 +0200
                      Re: [PATCH v4 04/14] x86/rtc: replace paravirt rtc check with  platform legacy quirk Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-04-08 14:40 +0200
                        Re: [PATCH v4 04/14] x86/rtc: replace paravirt rtc check with  platform legacy quirk "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-04-08 20:50 +0200
            Re: [PATCH v4 04/14] x86/rtc: replace paravirt rtc check with  platform legacy quirk "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-04-08 08:40 +0200
              Re: [PATCH v4 04/14] x86/rtc: replace paravirt rtc check with  platform legacy quirk Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-04-08 14:30 +0200
    [PATCH v4 07/14] tools/lguest: force disable tboot and apm "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-04-07 02:10 +0200
      Re: [PATCH v4 07/14] tools/lguest: force disable tboot and apm Rusty Russell <rusty@rustcorp.com.au> - 2016-04-11 06:00 +0200
    [PATCH v4 03/14] tools/lguest: make lguest launcher use X86_SUBARCH_LGUEST explicitly "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-04-07 02:10 +0200
    [PATCH v4 08/14] apm32: remove paravirt_enabled() use "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-04-07 02:10 +0200
      Re: [PATCH v4 08/14] apm32: remove paravirt_enabled() use Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-04-07 15:10 +0200
        Re: [PATCH v4 08/14] apm32: remove paravirt_enabled() use "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-04-08 00:40 +0200
    [PATCH v4 12/14] x86, ACPI: parse ACPI_FADT_LEGACY_DEVICES "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-04-07 02:10 +0200
    [PATCH v4 01/14] x86/boot: enumerate documentation for the x86 hardware_subarch "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-04-07 02:10 +0200
      Re: [PATCH v4 01/14] x86/boot: enumerate documentation for the x86  hardware_subarch Andy Shevchenko <andriy.shevchenko@linux.intel.com> - 2016-04-07 13:30 +0200
        Re: [PATCH v4 01/14] x86/boot: enumerate documentation for the x86  hardware_subarch "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-04-08 00:40 +0200
    [PATCH v4 09/14] x86/tboot: remove paravirt_enabled() "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-04-07 02:10 +0200
    [PATCH v4 02/14] x86/xen: use X86_SUBARCH_XEN for PV guest boots "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-04-07 02:20 +0200
      Re: [Xen-devel] [PATCH v4 02/14] x86/xen: use X86_SUBARCH_XEN for PV  guest boots David Vrabel <david.vrabel@citrix.com> - 2016-04-07 11:50 +0200
    [PATCH v4 05/14] x86, ACPI: move ACPI_FADT_NO_CMOS_RTC check to ACPI boot code "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-04-07 02:20 +0200
    Re: [Xen-devel] [PATCH v4 00/14] x86: remove paravirt_enabled Juergen Gross <jgross@suse.com> - 2016-04-07 15:30 +0200
    [PATCH v4 13/14] x86/init: rename ebda code file "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-04-07 23:40 +0200
    Re: [PATCH v4 00/14] x86: remove paravirt_enabled "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-04-08 03:20 +0200
      Re: [PATCH v4 00/14] x86: remove paravirt_enabled Borislav Petkov <bp@alien8.de> - 2016-04-08 12:30 +0200

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#1372962 — [PATCH v4 00/14] x86: remove paravirt_enabled

Now that Andy's ASM paravirt_enabled() use is merged all we need is to address
the rest of the C code uses. This completes that work by providing proper
semantics for platform legacy settings and quirks as suggested by Ingo, this in
turn can also be extended later for benefit of further processing of ACPI
5.2.9.3 IA-PC Boot Architecture flags, which we currently don't take much
advantage of.  For instance the ACPI_FADT_NO_VGA can later be leveraged by bare
metal x86 *and* HVMLite, as HVMLite seems to plan to set this.

Also, hpa has noted both Intel MID and CE4100 can make use of disabling
pnpbios, we can do that separately after this, but it should now be a
trivial change, generic given this quirk stuff is all generic now.

This patches goes tested by 0-day, except for the last patch, for some reason
the branch that included that patch has had testing delayed for quite a
while now, but I can't think of anything there that should break anything.

I've also just run time tested this on bare metal only so far.

Luis R. Rodriguez (14):
  x86/boot: enumerate documentation for the x86 hardware_subarch
  x86/xen: use X86_SUBARCH_XEN for PV guest boots
  tools/lguest: make lguest launcher use X86_SUBARCH_LGUEST explicitly
  x86/rtc: replace paravirt rtc check with platform legacy quirk
  x86, ACPI: move ACPI_FADT_NO_CMOS_RTC check to ACPI boot code
  x86/init: use a platform legacy quirk for ebda
  tools/lguest: force disable tboot and apm
  apm32: remove paravirt_enabled() use
  x86/tboot: remove paravirt_enabled()
  x86/cpu/intel: remove not needed paravirt_enabled() for f00f work
    around
  pnpbios: replace paravirt_enabled() check with legacy device check
  x86, ACPI: parse ACPI_FADT_LEGACY_DEVICES
  x86/init: rename ebda code file
  x86/paravirt: remove paravirt_enabled()

 arch/x86/Makefile                     |  3 ++-
 arch/x86/include/asm/paravirt.h       | 11 ---------
 arch/x86/include/asm/paravirt_types.h |  6 -----
 arch/x86/include/asm/processor.h      |  2 --
 arch/x86/include/asm/x86_init.h       | 42 +++++++++++++++++++++++++++++++++++
 arch/x86/include/uapi/asm/bootparam.h | 36 +++++++++++++++++++++++++++++-
 arch/x86/kernel/Makefile              |  6 ++++-
 arch/x86/kernel/acpi/boot.c           |  9 ++++++++
 arch/x86/kernel/apm_32.c              |  2 +-
 arch/x86/kernel/cpu/intel.c           |  2 +-
 arch/x86/kernel/{head.c => ebda.c}    |  2 +-
 arch/x86/kernel/head32.c              |  2 ++
 arch/x86/kernel/head64.c              |  1 +
 arch/x86/kernel/kvm.c                 |  8 -------
 arch/x86/kernel/paravirt.c            |  1 -
 arch/x86/kernel/platform-quirks.c     | 32 ++++++++++++++++++++++++++
 arch/x86/kernel/rtc.c                 | 15 ++-----------
 arch/x86/kernel/tboot.c               |  6 -----
 arch/x86/lguest/boot.c                |  3 ---
 arch/x86/xen/enlighten.c              |  5 +----
 drivers/pnp/pnpbios/core.c            |  3 ++-
 include/linux/pnp.h                   |  2 ++
 tools/lguest/lguest.c                 | 10 +++++++--
 23 files changed, 146 insertions(+), 63 deletions(-)
 rename arch/x86/kernel/{head.c => ebda.c} (98%)
 create mode 100644 arch/x86/kernel/platform-quirks.c

-- 
2.7.2

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#1372963 — [PATCH v4 06/14] x86/init: use a platform legacy quirk for ebda

This replaces the paravirt_enabled() check with a
proper x86 legacy platform quirk.

Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>
---
 arch/x86/include/asm/x86_init.h   | 3 +++
 arch/x86/kernel/head.c            | 2 +-
 arch/x86/kernel/platform-quirks.c | 4 ++++
 3 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/x86_init.h b/arch/x86/include/asm/x86_init.h
index 27d5c3fe5198..f3f81122ae3b 100644
--- a/arch/x86/include/asm/x86_init.h
+++ b/arch/x86/include/asm/x86_init.h
@@ -145,9 +145,12 @@ struct timespec;
  * struct x86_legacy_features - legacy x86 features
  *
  * @rtc: this device has a CMOS real-time clock present
+ * @ebda_search: it's safe to search for the EBDA signature in the hardware's
+ * 	low RAM
  */
 struct x86_legacy_features {
 	int rtc;
+	int ebda_search;
 };
 
 /**
diff --git a/arch/x86/kernel/head.c b/arch/x86/kernel/head.c
index 992f442ca155..afe65dffee80 100644
--- a/arch/x86/kernel/head.c
+++ b/arch/x86/kernel/head.c
@@ -38,7 +38,7 @@ void __init reserve_ebda_region(void)
 	 * that the paravirt case can handle memory setup
 	 * correctly, without our help.
 	 */
-	if (paravirt_enabled())
+	if (!x86_platform.legacy.ebda_search)
 		return;
 
 	/* end of low (conventional) memory */
diff --git a/arch/x86/kernel/platform-quirks.c b/arch/x86/kernel/platform-quirks.c
index 1b114ac5996f..a871b6b0e35f 100644
--- a/arch/x86/kernel/platform-quirks.c
+++ b/arch/x86/kernel/platform-quirks.c
@@ -7,8 +7,12 @@
 void __init x86_early_init_platform_quirks(void)
 {
 	x86_platform.legacy.rtc = 1;
+	x86_platform.legacy.ebda_search = 0;
 
 	switch (boot_params.hdr.hardware_subarch) {
+	case X86_SUBARCH_PC:
+		x86_platform.legacy.ebda_search = 1;
+		break;
 	case X86_SUBARCH_XEN:
 	case X86_SUBARCH_LGUEST:
 	case X86_SUBARCH_INTEL_MID:
-- 
2.7.2

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#1373214 — Re: [Xen-devel] [PATCH v4 06/14] x86/init: use a platform legacy quirk for ebda

On 07/04/16 01:06, Luis R. Rodriguez wrote:
> 
> --- a/arch/x86/kernel/platform-quirks.c
> +++ b/arch/x86/kernel/platform-quirks.c
> @@ -7,8 +7,12 @@
>  void __init x86_early_init_platform_quirks(void)
>  {
>  	x86_platform.legacy.rtc = 1;
> +	x86_platform.legacy.ebda_search = 0;

You should make the default the setting for regular PC hardware, as you
have done for the .rtc bit.

David

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#1373767 — Re: [Xen-devel] [PATCH v4 06/14] x86/init: use a platform legacy quirk for ebda

On Thu, Apr 07, 2016 at 10:44:50AM +0100, David Vrabel wrote:
> On 07/04/16 01:06, Luis R. Rodriguez wrote:
> > 
> > --- a/arch/x86/kernel/platform-quirks.c
> > +++ b/arch/x86/kernel/platform-quirks.c
> > @@ -7,8 +7,12 @@
> >  void __init x86_early_init_platform_quirks(void)
> >  {
> >  	x86_platform.legacy.rtc = 1;
> > +	x86_platform.legacy.ebda_search = 0;
> 
> You should make the default the setting for regular PC hardware, as you
> have done for the .rtc bit.

I went with with Ingo's suggested template [0]. Ingo, let me know what
you prefer.

[0] http://lkml.kernel.org/r/20160407205902.GS1990@wotan.suse.de

  Luis

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#1372965 — [PATCH v4 10/14] x86/cpu/intel: remove not needed paravirt_enabled() for f00f work around

The X86_BUG_F00F work around is responsible for fixing up the error
generated on attempted F00F exploitation from an OOPS to a SIGILL.
There is no reason why this code should not be allowed to run on
PV guest on a F00F-affected CPU -- it would simply never trigger.
The pv_enabled() check was there only to avoid printing the f00f
workaround, so removing the check is purely a cosmetic change.

Suggested-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>
---
 arch/x86/kernel/cpu/intel.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index f71a34944b56..66509285ffdd 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -233,7 +233,7 @@ static void intel_workarounds(struct cpuinfo_x86 *c)
 	 * The Quark is also family 5, but does not have the same bug.
 	 */
 	clear_cpu_bug(c, X86_BUG_F00F);
-	if (!paravirt_enabled() && c->x86 == 5 && c->x86_model < 9) {
+	if (c->x86 == 5 && c->x86_model < 9) {
 		static int f00f_workaround_enabled;
 
 		set_cpu_bug(c, X86_BUG_F00F);
-- 
2.7.2

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#1372966 — [PATCH v4 14/14] x86/paravirt: remove paravirt_enabled()

That that paravirt_enabled() is replaced with proper
x86 semantics we can remove it.

Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>
---
 arch/x86/include/asm/paravirt.h       | 5 -----
 arch/x86/include/asm/paravirt_types.h | 1 -
 arch/x86/include/asm/processor.h      | 1 -
 arch/x86/kernel/kvm.c                 | 8 --------
 arch/x86/kernel/paravirt.c            | 1 -
 arch/x86/lguest/boot.c                | 2 --
 arch/x86/xen/enlighten.c              | 1 -
 7 files changed, 19 deletions(-)

diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index 6c7a4a192032..dff26bc91b17 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -15,11 +15,6 @@
 #include <linux/cpumask.h>
 #include <asm/frame.h>
 
-static inline int paravirt_enabled(void)
-{
-	return pv_info.paravirt_enabled;
-}
-
 static inline void load_sp0(struct tss_struct *tss,
 			     struct thread_struct *thread)
 {
diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
index 6acc1b26cf40..7fedf24bd811 100644
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -69,7 +69,6 @@ struct pv_info {
 	u16 extra_user_64bit_cs;  /* __USER_CS if none */
 #endif
 
-	int paravirt_enabled;
 	const char *name;
 };
 
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 0c70c7daa6b8..8d326e822cb8 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -473,7 +473,6 @@ static inline unsigned long current_top_of_stack(void)
 #include <asm/paravirt.h>
 #else
 #define __cpuid			native_cpuid
-#define paravirt_enabled()	0
 
 static inline void load_sp0(struct tss_struct *tss,
 			    struct thread_struct *thread)
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index dc1207e2f193..eea2a6f72b31 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -285,14 +285,6 @@ static void __init paravirt_ops_setup(void)
 {
 	pv_info.name = "KVM";
 
-	/*
-	 * KVM isn't paravirt in the sense of paravirt_enabled.  A KVM
-	 * guest kernel works like a bare metal kernel with additional
-	 * features, and paravirt_enabled is about features that are
-	 * missing.
-	 */
-	pv_info.paravirt_enabled = 0;
-
 	if (kvm_para_has_feature(KVM_FEATURE_NOP_IO_DELAY))
 		pv_cpu_ops.io_delay = kvm_io_delay;
 
diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index f08ac28b8136..71a2d8a05a66 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -294,7 +294,6 @@ enum paravirt_lazy_mode paravirt_get_lazy_mode(void)
 
 struct pv_info pv_info = {
 	.name = "bare hardware",
-	.paravirt_enabled = 0,
 	.kernel_rpl = 0,
 	.shared_kernel_pmd = 1,	/* Only used when CONFIG_X86_PAE is set */
 
diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c
index f5497ee5fd2f..3847e736702e 100644
--- a/arch/x86/lguest/boot.c
+++ b/arch/x86/lguest/boot.c
@@ -1408,8 +1408,6 @@ __init void lguest_init(void)
 {
 	/* We're under lguest. */
 	pv_info.name = "lguest";
-	/* Paravirt is enabled. */
-	pv_info.paravirt_enabled = 1;
 	/* We're running at privilege level 1, not 0 as normal. */
 	pv_info.kernel_rpl = 1;
 	/* Everyone except Xen runs with this set. */
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 7449f268d687..d4bb70e9372e 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1186,7 +1186,6 @@ static unsigned xen_patch(u8 type, u16 clobbers, void *insnbuf,
 }
 
 static const struct pv_info xen_info __initconst = {
-	.paravirt_enabled = 1,
 	.shared_kernel_pmd = 0,
 
 #ifdef CONFIG_X86_64
-- 
2.7.2

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#1372967 — [PATCH v4 13/14] x86/init: rename ebda code file

This makes it clearer what this is.

Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>
---
 arch/x86/Makefile                  | 2 +-
 arch/x86/kernel/Makefile           | 2 +-
 arch/x86/kernel/{head.c => ebda.c} | 0
 3 files changed, 2 insertions(+), 2 deletions(-)
 rename arch/x86/kernel/{head.c => ebda.c} (100%)

diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index f9ed8a7ce2b6..6fce7f096b88 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -208,7 +208,7 @@ endif
 
 head-y := arch/x86/kernel/head_$(BITS).o
 head-y += arch/x86/kernel/head$(BITS).o
-head-y += arch/x86/kernel/head.o
+head-y += arch/x86/kernel/ebda.o
 head-y += arch/x86/kernel/platform-quirks.o
 
 libs-y  += arch/x86/lib/
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 7a9e44d935de..0503f5bfb18d 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -4,7 +4,7 @@
 
 extra-y	:= head_$(BITS).o
 extra-y	+= head$(BITS).o
-extra-y	+= head.o
+extra-y	+= ebda.o
 extra-y	+= platform-quirks.o
 extra-y	+= vmlinux.lds
 
diff --git a/arch/x86/kernel/head.c b/arch/x86/kernel/ebda.c
similarity index 100%
rename from arch/x86/kernel/head.c
rename to arch/x86/kernel/ebda.c
-- 
2.7.2

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#1372969 — [PATCH v4 04/14] x86/rtc: replace paravirt rtc check with platform legacy quirk

We have 4 types of x86 platforms that disable RTC:

  * Intel MID
  * Lguest - uses paravirt
  * Xen dom-U - uses paravirt
  * x86 on legacy systems annotated with an ACPI legacy flag

We can consolidate all of these into a platform specific legacy
quirk set early in boot through i386_start_kernel() and through
x86_64_start_reservations(). This deals with the RTC quirks which
we can rely on through the hardware subarch, the ACPI check can
be dealt with separately.

v2: split the subarch check from the ACPI check, clarify
    on the ACPI change commit log why ordering works

Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>
---
 arch/x86/Makefile                     |  1 +
 arch/x86/include/asm/paravirt.h       |  6 ------
 arch/x86/include/asm/paravirt_types.h |  5 -----
 arch/x86/include/asm/processor.h      |  1 -
 arch/x86/include/asm/x86_init.h       | 13 +++++++++++++
 arch/x86/kernel/Makefile              |  6 +++++-
 arch/x86/kernel/head32.c              |  2 ++
 arch/x86/kernel/head64.c              |  1 +
 arch/x86/kernel/platform-quirks.c     | 18 ++++++++++++++++++
 arch/x86/kernel/rtc.c                 |  7 ++-----
 arch/x86/lguest/boot.c                |  1 -
 arch/x86/xen/enlighten.c              |  3 ---
 12 files changed, 42 insertions(+), 22 deletions(-)
 create mode 100644 arch/x86/kernel/platform-quirks.c

diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 4086abca0b32..f9ed8a7ce2b6 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -209,6 +209,7 @@ endif
 head-y := arch/x86/kernel/head_$(BITS).o
 head-y += arch/x86/kernel/head$(BITS).o
 head-y += arch/x86/kernel/head.o
+head-y += arch/x86/kernel/platform-quirks.o
 
 libs-y  += arch/x86/lib/
 
diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index 601f1b8f9961..6c7a4a192032 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -20,12 +20,6 @@ static inline int paravirt_enabled(void)
 	return pv_info.paravirt_enabled;
 }
 
-static inline int paravirt_has_feature(unsigned int feature)
-{
-	WARN_ON_ONCE(!pv_info.paravirt_enabled);
-	return (pv_info.features & feature);
-}
-
 static inline void load_sp0(struct tss_struct *tss,
 			     struct thread_struct *thread)
 {
diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
index e8c2326478c8..6acc1b26cf40 100644
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -70,14 +70,9 @@ struct pv_info {
 #endif
 
 	int paravirt_enabled;
-	unsigned int features;	  /* valid only if paravirt_enabled is set */
 	const char *name;
 };
 
-#define paravirt_has(x) paravirt_has_feature(PV_SUPPORTED_##x)
-/* Supported features */
-#define PV_SUPPORTED_RTC        (1<<0)
-
 struct pv_init_ops {
 	/*
 	 * Patch may replace one of the defined code sequences with
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 9264476f3d57..0c70c7daa6b8 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -474,7 +474,6 @@ static inline unsigned long current_top_of_stack(void)
 #else
 #define __cpuid			native_cpuid
 #define paravirt_enabled()	0
-#define paravirt_has(x) 	0
 
 static inline void load_sp0(struct tss_struct *tss,
 			    struct thread_struct *thread)
diff --git a/arch/x86/include/asm/x86_init.h b/arch/x86/include/asm/x86_init.h
index 1ae89a2721d6..27d5c3fe5198 100644
--- a/arch/x86/include/asm/x86_init.h
+++ b/arch/x86/include/asm/x86_init.h
@@ -142,6 +142,15 @@ struct x86_cpuinit_ops {
 struct timespec;
 
 /**
+ * struct x86_legacy_features - legacy x86 features
+ *
+ * @rtc: this device has a CMOS real-time clock present
+ */
+struct x86_legacy_features {
+	int rtc;
+};
+
+/**
  * struct x86_platform_ops - platform specific runtime functions
  * @calibrate_tsc:		calibrate TSC
  * @get_wallclock:		get time from HW clock like RTC etc.
@@ -152,6 +161,7 @@ struct timespec;
  * @save_sched_clock_state:	save state for sched_clock() on suspend
  * @restore_sched_clock_state:	restore state for sched_clock() on resume
  * @apic_post_init:		adjust apic if neeeded
+ * @legacy:			legacy features
  */
 struct x86_platform_ops {
 	unsigned long (*calibrate_tsc)(void);
@@ -165,6 +175,7 @@ struct x86_platform_ops {
 	void (*save_sched_clock_state)(void);
 	void (*restore_sched_clock_state)(void);
 	void (*apic_post_init)(void);
+	struct x86_legacy_features legacy;
 };
 
 struct pci_dev;
@@ -186,6 +197,8 @@ extern struct x86_cpuinit_ops x86_cpuinit;
 extern struct x86_platform_ops x86_platform;
 extern struct x86_msi_ops x86_msi;
 extern struct x86_io_apic_ops x86_io_apic_ops;
+
+extern void x86_early_init_platform_quirks(void);
 extern void x86_init_noop(void);
 extern void x86_init_uint_noop(unsigned int unused);
 
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 89f8ade0bc7c..7a9e44d935de 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -2,7 +2,11 @@
 # Makefile for the linux kernel.
 #
 
-extra-y                := head_$(BITS).o head$(BITS).o head.o vmlinux.lds
+extra-y	:= head_$(BITS).o
+extra-y	+= head$(BITS).o
+extra-y	+= head.o
+extra-y	+= platform-quirks.o
+extra-y	+= vmlinux.lds
 
 CPPFLAGS_vmlinux.lds += -U$(UTS_MACHINE)
 
diff --git a/arch/x86/kernel/head32.c b/arch/x86/kernel/head32.c
index 2911ef3a9f1c..d784bb547a9d 100644
--- a/arch/x86/kernel/head32.c
+++ b/arch/x86/kernel/head32.c
@@ -34,6 +34,8 @@ asmlinkage __visible void __init i386_start_kernel(void)
 	cr4_init_shadow();
 	sanitize_boot_params(&boot_params);
 
+	x86_early_init_platform_quirks();
+
 	/* Call the subarch specific early setup function */
 	switch (boot_params.hdr.hardware_subarch) {
 	case X86_SUBARCH_INTEL_MID:
diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index 1f4422d5c8d0..b72fb0b71dd1 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -182,6 +182,7 @@ void __init x86_64_start_reservations(char *real_mode_data)
 	if (!boot_params.hdr.version)
 		copy_bootdata(__va(real_mode_data));
 
+	x86_early_init_platform_quirks();
 	reserve_ebda_region();
 
 	switch (boot_params.hdr.hardware_subarch) {
diff --git a/arch/x86/kernel/platform-quirks.c b/arch/x86/kernel/platform-quirks.c
new file mode 100644
index 000000000000..1b114ac5996f
--- /dev/null
+++ b/arch/x86/kernel/platform-quirks.c
@@ -0,0 +1,18 @@
+#include <linux/kernel.h>
+#include <linux/init.h>
+
+#include <asm/setup.h>
+#include <asm/bios_ebda.h>
+
+void __init x86_early_init_platform_quirks(void)
+{
+	x86_platform.legacy.rtc = 1;
+
+	switch (boot_params.hdr.hardware_subarch) {
+	case X86_SUBARCH_XEN:
+	case X86_SUBARCH_LGUEST:
+	case X86_SUBARCH_INTEL_MID:
+		x86_platform.legacy.rtc = 0;
+		break;
+	}
+}
diff --git a/arch/x86/kernel/rtc.c b/arch/x86/kernel/rtc.c
index 4af8d063fb36..62c48da3889d 100644
--- a/arch/x86/kernel/rtc.c
+++ b/arch/x86/kernel/rtc.c
@@ -14,6 +14,7 @@
 #include <asm/time.h>
 #include <asm/intel-mid.h>
 #include <asm/rtc.h>
+#include <asm/setup.h>
 
 #ifdef CONFIG_X86_32
 /*
@@ -188,10 +189,6 @@ static __init int add_rtc_cmos(void)
 	if (of_have_populated_dt())
 		return 0;
 
-	/* Intel MID platforms don't have ioport rtc */
-	if (intel_mid_identify_cpu())
-		return -ENODEV;
-
 #ifdef CONFIG_ACPI
 	if (acpi_gbl_FADT.boot_flags & ACPI_FADT_NO_CMOS_RTC) {
 		/* This warning can likely go away again in a year or two. */
@@ -200,7 +197,7 @@ static __init int add_rtc_cmos(void)
 	}
 #endif
 
-	if (paravirt_enabled() && !paravirt_has(RTC))
+	if (!x86_platform.legacy.rtc)
 		return -ENODEV;
 
 	platform_device_register(&rtc_device);
diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c
index fd57d3ae7e16..f5497ee5fd2f 100644
--- a/arch/x86/lguest/boot.c
+++ b/arch/x86/lguest/boot.c
@@ -1414,7 +1414,6 @@ __init void lguest_init(void)
 	pv_info.kernel_rpl = 1;
 	/* Everyone except Xen runs with this set. */
 	pv_info.shared_kernel_pmd = 1;
-	pv_info.features = 0;
 
 	/*
 	 * We set up all the lguest overrides for sensitive operations.  These
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 40487f1ecb4c..7449f268d687 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1192,7 +1192,6 @@ static const struct pv_info xen_info __initconst = {
 #ifdef CONFIG_X86_64
 	.extra_user_64bit_cs = FLAT_USER_CS64,
 #endif
-	.features = 0,
 	.name = "Xen",
 };
 
@@ -1525,8 +1524,6 @@ asmlinkage __visible void __init xen_start_kernel(void)
 
 	/* Install Xen paravirt ops */
 	pv_info = xen_info;
-	if (xen_initial_domain())
-		pv_info.features |= PV_SUPPORTED_RTC;
 	pv_init_ops = xen_init_ops;
 	if (!xen_pvh_domain()) {
 		pv_cpu_ops = xen_cpu_ops;
-- 
2.7.2

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#1373224 — Re: [Xen-devel] [PATCH v4 04/14] x86/rtc: replace paravirt rtc check with platform legacy quirk

On 07/04/16 01:06, Luis R. Rodriguez wrote:
> We have 4 types of x86 platforms that disable RTC:
> 
>   * Intel MID
>   * Lguest - uses paravirt
>   * Xen dom-U - uses paravirt
>   * x86 on legacy systems annotated with an ACPI legacy flag
> 
> We can consolidate all of these into a platform specific legacy
> quirk set early in boot through i386_start_kernel() and through
> x86_64_start_reservations(). This deals with the RTC quirks which
> we can rely on through the hardware subarch, the ACPI check can
> be dealt with separately.

Xen parts:

Reviewed-by: David Vrabel <david.vrabel@citrix.com>

David

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#1378334 — Re: [Xen-devel] [PATCH v4 04/14] x86/rtc: replace paravirt rtc check with platform legacy quirk

On Thu, Apr 7, 2016 at 2:42 AM, David Vrabel <david.vrabel@citrix.com> wrote:
> On 07/04/16 01:06, Luis R. Rodriguez wrote:
>> We have 4 types of x86 platforms that disable RTC:
>>
>>   * Intel MID
>>   * Lguest - uses paravirt
>>   * Xen dom-U - uses paravirt
>>   * x86 on legacy systems annotated with an ACPI legacy flag
>>
>> We can consolidate all of these into a platform specific legacy
>> quirk set early in boot through i386_start_kernel() and through
>> x86_64_start_reservations(). This deals with the RTC quirks which
>> we can rely on through the hardware subarch, the ACPI check can
>> be dealt with separately.
>
> Xen parts:
>
> Reviewed-by: David Vrabel <david.vrabel@citrix.com>

So for instance, I dropped this Reviewed-by given that after this
someone pointed out dom0 as an issue and then I addressed that. Hope
to get a Reviewed-by or Acked-by for v6 then, which will also have the
added __init on xen_dom0_set_legacy_features() as requested by
Juergen.

 Luis

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#1373373 — Re: [PATCH v4 04/14] x86/rtc: replace paravirt rtc check with platform legacy quirk

On 04/06/2016 08:06 PM, Luis R. Rodriguez wrote:
> We have 4 types of x86 platforms that disable RTC:
>
>    * Intel MID
>    * Lguest - uses paravirt
>    * Xen dom-U - uses paravirt
>    * x86 on legacy systems annotated with an ACPI legacy flag
>
> We can consolidate all of these into a platform specific legacy
> quirk set early in boot through i386_start_kernel() and through
> x86_64_start_reservations(). This deals with the RTC quirks which
> we can rely on through the hardware subarch, the ACPI check can
> be dealt with separately.
>
> v2: split the subarch check from the ACPI check, clarify
>      on the ACPI change commit log why ordering works
>
> Suggested-by: Ingo Molnar <mingo@kernel.org>
> Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>
> ---
>   arch/x86/Makefile                     |  1 +
>   arch/x86/include/asm/paravirt.h       |  6 ------
>   arch/x86/include/asm/paravirt_types.h |  5 -----
>   arch/x86/include/asm/processor.h      |  1 -
>   arch/x86/include/asm/x86_init.h       | 13 +++++++++++++
>   arch/x86/kernel/Makefile              |  6 +++++-
>   arch/x86/kernel/head32.c              |  2 ++
>   arch/x86/kernel/head64.c              |  1 +
>   arch/x86/kernel/platform-quirks.c     | 18 ++++++++++++++++++
>   arch/x86/kernel/rtc.c                 |  7 ++-----
>   arch/x86/lguest/boot.c                |  1 -
>   arch/x86/xen/enlighten.c              |  3 ---
>   12 files changed, 42 insertions(+), 22 deletions(-)
>   create mode 100644 arch/x86/kernel/platform-quirks.c
>
> diff --git a/arch/x86/Makefile b/arch/x86/Makefile
> index 4086abca0b32..f9ed8a7ce2b6 100644
> --- a/arch/x86/Makefile
> +++ b/arch/x86/Makefile
> @@ -209,6 +209,7 @@ endif
>   head-y := arch/x86/kernel/head_$(BITS).o
>   head-y += arch/x86/kernel/head$(BITS).o
>   head-y += arch/x86/kernel/head.o
> +head-y += arch/x86/kernel/platform-quirks.o
>   
>   libs-y  += arch/x86/lib/
>   
> diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
> index 601f1b8f9961..6c7a4a192032 100644
> --- a/arch/x86/include/asm/paravirt.h
> +++ b/arch/x86/include/asm/paravirt.h
> @@ -20,12 +20,6 @@ static inline int paravirt_enabled(void)
>   	return pv_info.paravirt_enabled;
>   }
>   
> -static inline int paravirt_has_feature(unsigned int feature)
> -{
> -	WARN_ON_ONCE(!pv_info.paravirt_enabled);
> -	return (pv_info.features & feature);
> -}
> -
>   static inline void load_sp0(struct tss_struct *tss,
>   			     struct thread_struct *thread)
>   {
> diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
> index e8c2326478c8..6acc1b26cf40 100644
> --- a/arch/x86/include/asm/paravirt_types.h
> +++ b/arch/x86/include/asm/paravirt_types.h
> @@ -70,14 +70,9 @@ struct pv_info {
>   #endif
>   
>   	int paravirt_enabled;
> -	unsigned int features;	  /* valid only if paravirt_enabled is set */
>   	const char *name;
>   };
>   
> -#define paravirt_has(x) paravirt_has_feature(PV_SUPPORTED_##x)
> -/* Supported features */
> -#define PV_SUPPORTED_RTC        (1<<0)
> -
>   struct pv_init_ops {
>   	/*
>   	 * Patch may replace one of the defined code sequences with
> diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
> index 9264476f3d57..0c70c7daa6b8 100644
> --- a/arch/x86/include/asm/processor.h
> +++ b/arch/x86/include/asm/processor.h
> @@ -474,7 +474,6 @@ static inline unsigned long current_top_of_stack(void)
>   #else
>   #define __cpuid			native_cpuid
>   #define paravirt_enabled()	0
> -#define paravirt_has(x) 	0
>   
>   static inline void load_sp0(struct tss_struct *tss,
>   			    struct thread_struct *thread)
> diff --git a/arch/x86/include/asm/x86_init.h b/arch/x86/include/asm/x86_init.h
> index 1ae89a2721d6..27d5c3fe5198 100644
> --- a/arch/x86/include/asm/x86_init.h
> +++ b/arch/x86/include/asm/x86_init.h
> @@ -142,6 +142,15 @@ struct x86_cpuinit_ops {
>   struct timespec;
>   
>   /**
> + * struct x86_legacy_features - legacy x86 features
> + *
> + * @rtc: this device has a CMOS real-time clock present
> + */
> +struct x86_legacy_features {
> +	int rtc;
> +};
> +
> +/**
>    * struct x86_platform_ops - platform specific runtime functions
>    * @calibrate_tsc:		calibrate TSC
>    * @get_wallclock:		get time from HW clock like RTC etc.
> @@ -152,6 +161,7 @@ struct timespec;
>    * @save_sched_clock_state:	save state for sched_clock() on suspend
>    * @restore_sched_clock_state:	restore state for sched_clock() on resume
>    * @apic_post_init:		adjust apic if neeeded
> + * @legacy:			legacy features
>    */
>   struct x86_platform_ops {
>   	unsigned long (*calibrate_tsc)(void);
> @@ -165,6 +175,7 @@ struct x86_platform_ops {
>   	void (*save_sched_clock_state)(void);
>   	void (*restore_sched_clock_state)(void);
>   	void (*apic_post_init)(void);
> +	struct x86_legacy_features legacy;
>   };
>   
>   struct pci_dev;
> @@ -186,6 +197,8 @@ extern struct x86_cpuinit_ops x86_cpuinit;
>   extern struct x86_platform_ops x86_platform;
>   extern struct x86_msi_ops x86_msi;
>   extern struct x86_io_apic_ops x86_io_apic_ops;
> +
> +extern void x86_early_init_platform_quirks(void);
>   extern void x86_init_noop(void);
>   extern void x86_init_uint_noop(unsigned int unused);
>   
> diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
> index 89f8ade0bc7c..7a9e44d935de 100644
> --- a/arch/x86/kernel/Makefile
> +++ b/arch/x86/kernel/Makefile
> @@ -2,7 +2,11 @@
>   # Makefile for the linux kernel.
>   #
>   
> -extra-y                := head_$(BITS).o head$(BITS).o head.o vmlinux.lds
> +extra-y	:= head_$(BITS).o
> +extra-y	+= head$(BITS).o
> +extra-y	+= head.o
> +extra-y	+= platform-quirks.o
> +extra-y	+= vmlinux.lds
>   
>   CPPFLAGS_vmlinux.lds += -U$(UTS_MACHINE)
>   
> diff --git a/arch/x86/kernel/head32.c b/arch/x86/kernel/head32.c
> index 2911ef3a9f1c..d784bb547a9d 100644
> --- a/arch/x86/kernel/head32.c
> +++ b/arch/x86/kernel/head32.c
> @@ -34,6 +34,8 @@ asmlinkage __visible void __init i386_start_kernel(void)
>   	cr4_init_shadow();
>   	sanitize_boot_params(&boot_params);
>   
> +	x86_early_init_platform_quirks();
> +
>   	/* Call the subarch specific early setup function */
>   	switch (boot_params.hdr.hardware_subarch) {
>   	case X86_SUBARCH_INTEL_MID:
> diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
> index 1f4422d5c8d0..b72fb0b71dd1 100644
> --- a/arch/x86/kernel/head64.c
> +++ b/arch/x86/kernel/head64.c
> @@ -182,6 +182,7 @@ void __init x86_64_start_reservations(char *real_mode_data)
>   	if (!boot_params.hdr.version)
>   		copy_bootdata(__va(real_mode_data));
>   
> +	x86_early_init_platform_quirks();
>   	reserve_ebda_region();
>   
>   	switch (boot_params.hdr.hardware_subarch) {
> diff --git a/arch/x86/kernel/platform-quirks.c b/arch/x86/kernel/platform-quirks.c
> new file mode 100644
> index 000000000000..1b114ac5996f
> --- /dev/null
> +++ b/arch/x86/kernel/platform-quirks.c
> @@ -0,0 +1,18 @@
> +#include <linux/kernel.h>
> +#include <linux/init.h>
> +
> +#include <asm/setup.h>
> +#include <asm/bios_ebda.h>
> +
> +void __init x86_early_init_platform_quirks(void)
> +{
> +	x86_platform.legacy.rtc = 1;
> +
> +	switch (boot_params.hdr.hardware_subarch) {
> +	case X86_SUBARCH_XEN:
> +	case X86_SUBARCH_LGUEST:
> +	case X86_SUBARCH_INTEL_MID:
> +		x86_platform.legacy.rtc = 0;
> +		break;
> +	}
> +}

What about Xen dom0 (aka initial domain)?

-boris

> --- a/arch/x86/xen/enlighten.c
> +++ b/arch/x86/xen/enlighten.c
> @@ -1192,7 +1192,6 @@ static const struct pv_info xen_info __initconst = {
>   #ifdef CONFIG_X86_64
>   	.extra_user_64bit_cs = FLAT_USER_CS64,
>   #endif
> -	.features = 0,
>   	.name = "Xen",
>   };
>   
> @@ -1525,8 +1524,6 @@ asmlinkage __visible void __init xen_start_kernel(void)
>   
>   	/* Install Xen paravirt ops */
>   	pv_info = xen_info;
> -	if (xen_initial_domain())
> -		pv_info.features |= PV_SUPPORTED_RTC;
>   	pv_init_ops = xen_init_ops;
>   	if (!xen_pvh_domain()) {
>   		pv_cpu_ops = xen_cpu_ops;

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#1373901 — Re: [PATCH v4 04/14] x86/rtc: replace paravirt rtc check with platform legacy quirk

On Thu, Apr 07, 2016 at 08:55:54AM -0400, Boris Ostrovsky wrote:
> On 04/06/2016 08:06 PM, Luis R. Rodriguez wrote:
> >We have 4 types of x86 platforms that disable RTC:
> >
> >   * Intel MID
> >   * Lguest - uses paravirt
> >   * Xen dom-U - uses paravirt
> >   * x86 on legacy systems annotated with an ACPI legacy flag
> >
> >We can consolidate all of these into a platform specific legacy
> >quirk set early in boot through i386_start_kernel() and through
> >x86_64_start_reservations(). This deals with the RTC quirks which
> >we can rely on through the hardware subarch, the ACPI check can
> >be dealt with separately.
> >
> >v2: split the subarch check from the ACPI check, clarify
> >     on the ACPI change commit log why ordering works
> >
> >Suggested-by: Ingo Molnar <mingo@kernel.org>
> >Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>

<-- snip -->

> >diff --git a/arch/x86/kernel/platform-quirks.c b/arch/x86/kernel/platform-quirks.c
> >new file mode 100644
> >index 000000000000..1b114ac5996f
> >--- /dev/null
> >+++ b/arch/x86/kernel/platform-quirks.c
> >@@ -0,0 +1,18 @@
> >+#include <linux/kernel.h>
> >+#include <linux/init.h>
> >+
> >+#include <asm/setup.h>
> >+#include <asm/bios_ebda.h>
> >+
> >+void __init x86_early_init_platform_quirks(void)
> >+{
> >+	x86_platform.legacy.rtc = 1;
> >+
> >+	switch (boot_params.hdr.hardware_subarch) {
> >+	case X86_SUBARCH_XEN:
> >+	case X86_SUBARCH_LGUEST:
> >+	case X86_SUBARCH_INTEL_MID:
> >+		x86_platform.legacy.rtc = 0;
> >+		break;
> >+	}
> >+}
> 
> What about Xen dom0 (aka initial domain)?

Indeed, thanks for catching this, the hunk below removes the re-enablement of
the the RTC for dom0:

> >--- a/arch/x86/xen/enlighten.c
> >+++ b/arch/x86/xen/enlighten.c
> >@@ -1192,7 +1192,6 @@ static const struct pv_info xen_info __initconst = {
> >  #ifdef CONFIG_X86_64
> >  	.extra_user_64bit_cs = FLAT_USER_CS64,
> >  #endif
> >-	.features = 0,
> >  	.name = "Xen",
> >  };
> >@@ -1525,8 +1524,6 @@ asmlinkage __visible void __init xen_start_kernel(void)
> >  	/* Install Xen paravirt ops */
> >  	pv_info = xen_info;
> >-	if (xen_initial_domain())
> >-		pv_info.features |= PV_SUPPORTED_RTC;
> >  	pv_init_ops = xen_init_ops;
> >  	if (!xen_pvh_domain()) {
> >  		pv_cpu_ops = xen_cpu_ops;

This should then break dom0 unless of course you have the respective next
patch applied and that disabled the RTC due to an ACPI setting on your
platform. Juergen, can you check to see if that was the case for your
testing platform on dom0 ?

This highlights a semantic gap issue. From a quick cursory review, I think
we can address this temporarily by just using a check:

void __init x86_early_init_platform_quirks(void)
{
	x86_platform.legacy.rtc = 1;

	switch (boot_params.hdr.hardware_subarch) {
	case X86_SUBARCH_XEN:
	case X86_SUBARCH_LGUEST:
	case X86_SUBARCH_INTEL_MID:
-		x86_platform.legacy.rtc = 0;
+		if (x86_init.mpparse.get_smp_config != x86_init_uint_noop)
+			x86_platform.legacy.rtc = 0;
		break;
	}
}

This would work given x86_early_init_platform_quirks() is called prior
to the any code that sets up x86_init.mpparse*, and the only code that
would have set this is the PV guest path, and the dom0 override. Is
would be replacing one hack with another though so I'm not exactly happy
with it as a compromise.

Another x86 standard thing dom0 populates on the PV path is
&boot_params.screen_info, done through xen_init_vga() -- but it
was not clear exactly what domU does with this ? Does domU never
have VGA set up? Given that the PV path is the only thing that would
ever set up the x86 zero page I take it domU leaves that empty,
and dom0 *always* seems to set up the screen_info->orig_video_isVGA,
so another mechanism might be something like:

void __init x86_early_init_platform_quirks(void)
{
+	struct screen_info *screen_info = &boot_params.screen_info;
+
	x86_platform.legacy.rtc = 1;

	switch (boot_params.hdr.hardware_subarch) {
	case X86_SUBARCH_XEN:
	case X86_SUBARCH_LGUEST:
	case X86_SUBARCH_INTEL_MID:
-		x86_platform.legacy.rtc = 0;
+		if (!screen_info->orig_video_isVGA)
+			x86_platform.legacy.rtc = 0;
		break;
	}
}

If the semantics of requiring VGA through the x86 boot params
suffice to annotate PV path dom0 then we have a win. Specially
if this might be useful to other virtualization environments
to do some of their own virtualization quirks in this path.

Additionally -- if domU never sets the screen info stuff, should
it or does it always set ACPI_FADT_NO_VGA as well ?

Is Xen the only guest type we have that has a notion of dom0 and need dom0 type
of quirks ? Also how would this work for HVMLite for domU and dom0 ? I think
the ARM folks are doing some things with EFI configuration tables to pass the
screen_info stuff, so perhaps that should be looked at.

  Luis

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#1373986 — Re: [PATCH v4 04/14] x86/rtc: replace paravirt rtc check with platform legacy quirk

On 08/04/16 02:32, Luis R. Rodriguez wrote:
> On Thu, Apr 07, 2016 at 08:55:54AM -0400, Boris Ostrovsky wrote:
>> On 04/06/2016 08:06 PM, Luis R. Rodriguez wrote:
>>> We have 4 types of x86 platforms that disable RTC:
>>>
>>>   * Intel MID
>>>   * Lguest - uses paravirt
>>>   * Xen dom-U - uses paravirt
>>>   * x86 on legacy systems annotated with an ACPI legacy flag
>>>
>>> We can consolidate all of these into a platform specific legacy
>>> quirk set early in boot through i386_start_kernel() and through
>>> x86_64_start_reservations(). This deals with the RTC quirks which
>>> we can rely on through the hardware subarch, the ACPI check can
>>> be dealt with separately.
>>>
>>> v2: split the subarch check from the ACPI check, clarify
>>>     on the ACPI change commit log why ordering works
>>>
>>> Suggested-by: Ingo Molnar <mingo@kernel.org>
>>> Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>
> 
> <-- snip -->
> 
>>> diff --git a/arch/x86/kernel/platform-quirks.c b/arch/x86/kernel/platform-quirks.c
>>> new file mode 100644
>>> index 000000000000..1b114ac5996f
>>> --- /dev/null
>>> +++ b/arch/x86/kernel/platform-quirks.c
>>> @@ -0,0 +1,18 @@
>>> +#include <linux/kernel.h>
>>> +#include <linux/init.h>
>>> +
>>> +#include <asm/setup.h>
>>> +#include <asm/bios_ebda.h>
>>> +
>>> +void __init x86_early_init_platform_quirks(void)
>>> +{
>>> +	x86_platform.legacy.rtc = 1;
>>> +
>>> +	switch (boot_params.hdr.hardware_subarch) {
>>> +	case X86_SUBARCH_XEN:
>>> +	case X86_SUBARCH_LGUEST:
>>> +	case X86_SUBARCH_INTEL_MID:
>>> +		x86_platform.legacy.rtc = 0;
>>> +		break;
>>> +	}
>>> +}
>>
>> What about Xen dom0 (aka initial domain)?
> 
> Indeed, thanks for catching this, the hunk below removes the re-enablement of
> the the RTC for dom0:
> 
>>> --- a/arch/x86/xen/enlighten.c
>>> +++ b/arch/x86/xen/enlighten.c
>>> @@ -1192,7 +1192,6 @@ static const struct pv_info xen_info __initconst = {
>>>  #ifdef CONFIG_X86_64
>>>  	.extra_user_64bit_cs = FLAT_USER_CS64,
>>>  #endif
>>> -	.features = 0,
>>>  	.name = "Xen",
>>>  };
>>> @@ -1525,8 +1524,6 @@ asmlinkage __visible void __init xen_start_kernel(void)
>>>  	/* Install Xen paravirt ops */
>>>  	pv_info = xen_info;
>>> -	if (xen_initial_domain())
>>> -		pv_info.features |= PV_SUPPORTED_RTC;
>>>  	pv_init_ops = xen_init_ops;
>>>  	if (!xen_pvh_domain()) {
>>>  		pv_cpu_ops = xen_cpu_ops;
> 
> This should then break dom0 unless of course you have the respective next
> patch applied and that disabled the RTC due to an ACPI setting on your
> platform. Juergen, can you check to see if that was the case for your
> testing platform on dom0 ?

Are you sure it would break? Wouldn't it just fall back to another
clock source, e.g. hpet?

I looked into my test system: seems as if add_rtc_cmos() is returning
before the .legacy.rtc test.

> This highlights a semantic gap issue. From a quick cursory review, I think
> we can address this temporarily by just using a check:
> 
> void __init x86_early_init_platform_quirks(void)
> {
> 	x86_platform.legacy.rtc = 1;
> 
> 	switch (boot_params.hdr.hardware_subarch) {
> 	case X86_SUBARCH_XEN:
> 	case X86_SUBARCH_LGUEST:
> 	case X86_SUBARCH_INTEL_MID:
> -		x86_platform.legacy.rtc = 0;
> +		if (x86_init.mpparse.get_smp_config != x86_init_uint_noop)
> +			x86_platform.legacy.rtc = 0;

No! Why don't you just use the explicit test xen_initial_domain() ?


Juergen

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#1374009 — Re: [PATCH v4 04/14] x86/rtc: replace paravirt rtc check with platform legacy quirk

On 08/04/16 08:29, Luis R. Rodriguez wrote:
> On Thu, Apr 7, 2016 at 10:18 PM, Juergen Gross <jgross@suse.com> wrote:
>> On 08/04/16 02:32, Luis R. Rodriguez wrote:
>>> This highlights a semantic gap issue. From a quick cursory review, I think
>>> we can address this temporarily by just using a check:
>>>
>>> void __init x86_early_init_platform_quirks(void)
>>> {
>>>       x86_platform.legacy.rtc = 1;
>>>
>>>       switch (boot_params.hdr.hardware_subarch) {
>>>       case X86_SUBARCH_XEN:
>>>       case X86_SUBARCH_LGUEST:
>>>       case X86_SUBARCH_INTEL_MID:
>>> -             x86_platform.legacy.rtc = 0;
>>> +             if (x86_init.mpparse.get_smp_config != x86_init_uint_noop)
>>> +                     x86_platform.legacy.rtc = 0;
>>
>> No! Why don't you just use the explicit test xen_initial_domain() ?
> 
> Because we don't want to sprinkle Xen specific code outside of Xen
> code. What do you think about the second possibility I listed?
> Otherwise, any other ideas?

Don't try to guess.

In case you don't want to inject Xen internals here, just call a Xen
function to either return the correct value, or to set all structure
elements correctly.

Thinking more about it: why not do that for all the subarchs? You'd
have the specific settings where they belong: in a subarch specific
source. Just do the default settings in x86_early_init_platform_quirks()
and let the subarch functions set the non-default values.


Juergen

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#1374017 — Re: [PATCH v4 04/14] x86/rtc: replace paravirt rtc check with platform legacy quirk

On Thu, Apr 7, 2016 at 11:38 PM, Juergen Gross <jgross@suse.com> wrote:
> On 08/04/16 08:29, Luis R. Rodriguez wrote:
>> On Thu, Apr 7, 2016 at 10:18 PM, Juergen Gross <jgross@suse.com> wrote:
>>> On 08/04/16 02:32, Luis R. Rodriguez wrote:
>>>> This highlights a semantic gap issue. From a quick cursory review, I think
>>>> we can address this temporarily by just using a check:
>>>>
>>>> void __init x86_early_init_platform_quirks(void)
>>>> {
>>>>       x86_platform.legacy.rtc = 1;
>>>>
>>>>       switch (boot_params.hdr.hardware_subarch) {
>>>>       case X86_SUBARCH_XEN:
>>>>       case X86_SUBARCH_LGUEST:
>>>>       case X86_SUBARCH_INTEL_MID:
>>>> -             x86_platform.legacy.rtc = 0;
>>>> +             if (x86_init.mpparse.get_smp_config != x86_init_uint_noop)
>>>> +                     x86_platform.legacy.rtc = 0;
>>>
>>> No! Why don't you just use the explicit test xen_initial_domain() ?
>>
>> Because we don't want to sprinkle Xen specific code outside of Xen
>> code. What do you think about the second possibility I listed?
>> Otherwise, any other ideas?
>
> Don't try to guess.

I can only do that given there is nothing at all to tell me what to
expect here with regards to RTC on Xen guest, if there is some
documentation that could help with that please let me know.

> In case you don't want to inject Xen internals here, just call a Xen
> function to either return the correct value, or to set all structure
> elements correctly.

I like the later as an option, in case there are further hardware
subarch specific quirks which require internal logistics. What do
others think?

> Thinking more about it: why not do that for all the subarchs?

I originally had went with that approach, but Ingo made the point that
it would be best to instead move all quirk settings into one place.
That lets a reader easily tell what is going on in one place, it also
compartmentalizes the hardware subarch uses.

> You'd
> have the specific settings where they belong: in a subarch specific
> source. Just do the default settings in x86_early_init_platform_quirks()
> and let the subarch functions set the non-default values.

This is a rather different approach than what I had originally tried.
Bike shed thing -- someone just has to decide.

Left up to me, I kind of really like centralizing the quirk settings
in one place approach as it means a reader can easily tell what's
going on regardless of platform in one place for odd settings. I
prefer this given that we *already* have the semantics over hardware
subarch in a generalized fashion. We *do not* have semantics for dom0
Vs domU -- if such a notion is generic to other virtualization
environments it deserves consideration to new semantics to deal with
that, otherwise the callback for handling further quirks is best, but
I'd also highly discourage such callback to be used.

 Luis

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#1374032 — Re: [PATCH v4 04/14] x86/rtc: replace paravirt rtc check with platform legacy quirk

On 08/04/16 08:56, Luis R. Rodriguez wrote:
> On Thu, Apr 7, 2016 at 11:38 PM, Juergen Gross <jgross@suse.com> wrote:
>> On 08/04/16 08:29, Luis R. Rodriguez wrote:
>>> On Thu, Apr 7, 2016 at 10:18 PM, Juergen Gross <jgross@suse.com> wrote:
>>>> On 08/04/16 02:32, Luis R. Rodriguez wrote:
>>>>> This highlights a semantic gap issue. From a quick cursory review, I think
>>>>> we can address this temporarily by just using a check:
>>>>>
>>>>> void __init x86_early_init_platform_quirks(void)
>>>>> {
>>>>>       x86_platform.legacy.rtc = 1;
>>>>>
>>>>>       switch (boot_params.hdr.hardware_subarch) {
>>>>>       case X86_SUBARCH_XEN:
>>>>>       case X86_SUBARCH_LGUEST:
>>>>>       case X86_SUBARCH_INTEL_MID:
>>>>> -             x86_platform.legacy.rtc = 0;
>>>>> +             if (x86_init.mpparse.get_smp_config != x86_init_uint_noop)
>>>>> +                     x86_platform.legacy.rtc = 0;
>>>>
>>>> No! Why don't you just use the explicit test xen_initial_domain() ?
>>>
>>> Because we don't want to sprinkle Xen specific code outside of Xen
>>> code. What do you think about the second possibility I listed?
>>> Otherwise, any other ideas?
>>
>> Don't try to guess.
> 
> I can only do that given there is nothing at all to tell me what to
> expect here with regards to RTC on Xen guest, if there is some
> documentation that could help with that please let me know.

Only Xen inernals. :-)

> 
>> In case you don't want to inject Xen internals here, just call a Xen
>> function to either return the correct value, or to set all structure
>> elements correctly.
> 
> I like the later as an option, in case there are further hardware
> subarch specific quirks which require internal logistics. What do
> others think?
> 
>> Thinking more about it: why not do that for all the subarchs?
> 
> I originally had went with that approach, but Ingo made the point that
> it would be best to instead move all quirk settings into one place.
> That lets a reader easily tell what is going on in one place, it also
> compartmentalizes the hardware subarch uses.

Okay. Another idea (not sure whether this is really a good one):

Add X86_SUBARCH_XEN_DOM0. As hardware_subarch is 32 bits wide I don't
think the number of subarchs is a scarce resource. :-)

I'd expect other quirks in future might have different settings for
domU and dom0, too.

>> You'd
>> have the specific settings where they belong: in a subarch specific
>> source. Just do the default settings in x86_early_init_platform_quirks()
>> and let the subarch functions set the non-default values.
> 
> This is a rather different approach than what I had originally tried.
> Bike shed thing -- someone just has to decide.
> 
> Left up to me, I kind of really like centralizing the quirk settings
> in one place approach as it means a reader can easily tell what's
> going on regardless of platform in one place for odd settings. I
> prefer this given that we *already* have the semantics over hardware
> subarch in a generalized fashion. We *do not* have semantics for dom0
> Vs domU -- if such a notion is generic to other virtualization

That's not carved in stone - see above. :-)

> environments it deserves consideration to new semantics to deal with
> that, otherwise the callback for handling further quirks is best, but
> I'd also highly discourage such callback to be used.


Juergen

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#1374041 — Re: [PATCH v4 04/14] x86/rtc: replace paravirt rtc check with platform legacy quirk

On Fri, Apr 8, 2016 at 12:13 AM, Juergen Gross <jgross@suse.com> wrote:
> On 08/04/16 08:56, Luis R. Rodriguez wrote:
>> On Thu, Apr 7, 2016 at 11:38 PM, Juergen Gross <jgross@suse.com> wrote:
>>> On 08/04/16 08:29, Luis R. Rodriguez wrote:
>>>> On Thu, Apr 7, 2016 at 10:18 PM, Juergen Gross <jgross@suse.com> wrote:
>>>>> On 08/04/16 02:32, Luis R. Rodriguez wrote:
>>>>>> This highlights a semantic gap issue. From a quick cursory review, I think
>>>>>> we can address this temporarily by just using a check:
>>>>>>
>>>>>> void __init x86_early_init_platform_quirks(void)
>>>>>> {
>>>>>>       x86_platform.legacy.rtc = 1;
>>>>>>
>>>>>>       switch (boot_params.hdr.hardware_subarch) {
>>>>>>       case X86_SUBARCH_XEN:
>>>>>>       case X86_SUBARCH_LGUEST:
>>>>>>       case X86_SUBARCH_INTEL_MID:
>>>>>> -             x86_platform.legacy.rtc = 0;
>>>>>> +             if (x86_init.mpparse.get_smp_config != x86_init_uint_noop)
>>>>>> +                     x86_platform.legacy.rtc = 0;
>>>>>
>>>>> No! Why don't you just use the explicit test xen_initial_domain() ?
>>>>
>>>> Because we don't want to sprinkle Xen specific code outside of Xen
>>>> code. What do you think about the second possibility I listed?
>>>> Otherwise, any other ideas?
>>>
>>> Don't try to guess.
>>
>> I can only do that given there is nothing at all to tell me what to
>> expect here with regards to RTC on Xen guest, if there is some
>> documentation that could help with that please let me know.
>
> Only Xen inernals. :-)

Where can I look at this specifically on the Xen sources? No worries
if you don't care -- as I don't really either.

>>> In case you don't want to inject Xen internals here, just call a Xen
>>> function to either return the correct value, or to set all structure
>>> elements correctly.
>>
>> I like the later as an option, in case there are further hardware
>> subarch specific quirks which require internal logistics. What do
>> others think?
>>
>>> Thinking more about it: why not do that for all the subarchs?
>>
>> I originally had went with that approach, but Ingo made the point that
>> it would be best to instead move all quirk settings into one place.
>> That lets a reader easily tell what is going on in one place, it also
>> compartmentalizes the hardware subarch uses.
>
> Okay. Another idea (not sure whether this is really a good one):
>
> Add X86_SUBARCH_XEN_DOM0. As hardware_subarch is 32 bits wide I don't
> think the number of subarchs is a scarce resource. :-)

This would mean bumping the x86 boot protocol, we shouldn't take that
lightly, but given that in this case the new subarch would really only
be set by the kernel (or future loaders for perhaps HVMLite) I'd think
this is not such an intrusive alternative.

> I'd expect other quirks in future might have different settings for
> domU and dom0, too.

Can you elaborate a bit more on this. I realize we expect domU and
dom0 on HVMLite in the future, would HVMLite use the subarch ? From
the last discussions on the HVMLite thread Boris noted HVMLite would
use the PC subarch -- how would we do dom0 Vs domU quirk management?

If it goes the EFI route, I gather Xen instead can use the EFI
configuration tables for Xen specific tunings, however we may also
need a generic x86 configuration table for generic quirks I think. We
may need to provide a 1-1 mapping of these quirks there, if the
subarch is not used.

>>> You'd
>>> have the specific settings where they belong: in a subarch specific
>>> source. Just do the default settings in x86_early_init_platform_quirks()
>>> and let the subarch functions set the non-default values.
>>
>> This is a rather different approach than what I had originally tried.
>> Bike shed thing -- someone just has to decide.
>>
>> Left up to me, I kind of really like centralizing the quirk settings
>> in one place approach as it means a reader can easily tell what's
>> going on regardless of platform in one place for odd settings. I
>> prefer this given that we *already* have the semantics over hardware
>> subarch in a generalized fashion. We *do not* have semantics for dom0
>> Vs domU -- if such a notion is generic to other virtualization
>
> That's not carved in stone - see above. :-)

Another subarch for Xen dom0 works well for me as well given the new
subarch would just all set in the kernel. It does mean extending the
x86 boot protocol though, and so for that I yield to hpa.

 Luis

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#1374068 — Re: [PATCH v4 04/14] x86/rtc: replace paravirt rtc check with platform legacy quirk

On 08/04/16 09:36, Luis R. Rodriguez wrote:
> On Fri, Apr 8, 2016 at 12:13 AM, Juergen Gross <jgross@suse.com> wrote:
>> On 08/04/16 08:56, Luis R. Rodriguez wrote:
>>> On Thu, Apr 7, 2016 at 11:38 PM, Juergen Gross <jgross@suse.com> wrote:
>>>> On 08/04/16 08:29, Luis R. Rodriguez wrote:
>>>>> On Thu, Apr 7, 2016 at 10:18 PM, Juergen Gross <jgross@suse.com> wrote:
>>>>>> On 08/04/16 02:32, Luis R. Rodriguez wrote:
>>>>>>> This highlights a semantic gap issue. From a quick cursory review, I think
>>>>>>> we can address this temporarily by just using a check:
>>>>>>>
>>>>>>> void __init x86_early_init_platform_quirks(void)
>>>>>>> {
>>>>>>>       x86_platform.legacy.rtc = 1;
>>>>>>>
>>>>>>>       switch (boot_params.hdr.hardware_subarch) {
>>>>>>>       case X86_SUBARCH_XEN:
>>>>>>>       case X86_SUBARCH_LGUEST:
>>>>>>>       case X86_SUBARCH_INTEL_MID:
>>>>>>> -             x86_platform.legacy.rtc = 0;
>>>>>>> +             if (x86_init.mpparse.get_smp_config != x86_init_uint_noop)
>>>>>>> +                     x86_platform.legacy.rtc = 0;
>>>>>>
>>>>>> No! Why don't you just use the explicit test xen_initial_domain() ?
>>>>>
>>>>> Because we don't want to sprinkle Xen specific code outside of Xen
>>>>> code. What do you think about the second possibility I listed?
>>>>> Otherwise, any other ideas?
>>>>
>>>> Don't try to guess.
>>>
>>> I can only do that given there is nothing at all to tell me what to
>>> expect here with regards to RTC on Xen guest, if there is some
>>> documentation that could help with that please let me know.
>>
>> Only Xen inernals. :-)
> 
> Where can I look at this specifically on the Xen sources? No worries
> if you don't care -- as I don't really either.

Just look how xen_initial_domain() is defined. :-)

>>>> In case you don't want to inject Xen internals here, just call a Xen
>>>> function to either return the correct value, or to set all structure
>>>> elements correctly.
>>>
>>> I like the later as an option, in case there are further hardware
>>> subarch specific quirks which require internal logistics. What do
>>> others think?
>>>
>>>> Thinking more about it: why not do that for all the subarchs?
>>>
>>> I originally had went with that approach, but Ingo made the point that
>>> it would be best to instead move all quirk settings into one place.
>>> That lets a reader easily tell what is going on in one place, it also
>>> compartmentalizes the hardware subarch uses.
>>
>> Okay. Another idea (not sure whether this is really a good one):
>>
>> Add X86_SUBARCH_XEN_DOM0. As hardware_subarch is 32 bits wide I don't
>> think the number of subarchs is a scarce resource. :-)
> 
> This would mean bumping the x86 boot protocol, we shouldn't take that
> lightly, but given that in this case the new subarch would really only
> be set by the kernel (or future loaders for perhaps HVMLite) I'd think
> this is not such an intrusive alternative.

I think adding an own subarch for dom0 isn't that bad. It really is
different from domU as dom0 has per default access to the real hardware
(or at least to most of it).

>> I'd expect other quirks in future might have different settings for
>> domU and dom0, too.
> 
> Can you elaborate a bit more on this.

I guess we might want to add other quirks in order to switch on/off
more features instead of doing this based on #ifdef or environment
tests. I'm thinking of current use, not of HVMlite specific stuff.

> I realize we expect domU and
> dom0 on HVMLite in the future, would HVMLite use the subarch ? From
> the last discussions on the HVMLite thread Boris noted HVMLite would
> use the PC subarch -- how would we do dom0 Vs domU quirk management?

This would have to be settled. I think it might be a good idea to
initialize the quirks to their defaults statically in x86_init.c
and just modify some as needed for HVMlite on early boot (e.g. in
the HVMlite or EFI stub). This will enable us to either make use of
subarch or not for HVMlite, just what fits best.

> If it goes the EFI route, I gather Xen instead can use the EFI
> configuration tables for Xen specific tunings, however we may also
> need a generic x86 configuration table for generic quirks I think. We
> may need to provide a 1-1 mapping of these quirks there, if the
> subarch is not used.

The EFI stub can set the quirks just according to it's needs. Going
this route would _require_ HVMlite is using the PC subarch, though,
in order to avoid overwriting the quirks in
x86_early_init_platform_quirks() later.

> 
>>>> You'd
>>>> have the specific settings where they belong: in a subarch specific
>>>> source. Just do the default settings in x86_early_init_platform_quirks()
>>>> and let the subarch functions set the non-default values.
>>>
>>> This is a rather different approach than what I had originally tried.
>>> Bike shed thing -- someone just has to decide.
>>>
>>> Left up to me, I kind of really like centralizing the quirk settings
>>> in one place approach as it means a reader can easily tell what's
>>> going on regardless of platform in one place for odd settings. I
>>> prefer this given that we *already* have the semantics over hardware
>>> subarch in a generalized fashion. We *do not* have semantics for dom0
>>> Vs domU -- if such a notion is generic to other virtualization
>>
>> That's not carved in stone - see above. :-)
> 
> Another subarch for Xen dom0 works well for me as well given the new
> subarch would just all set in the kernel. It does mean extending the
> x86 boot protocol though, and so for that I yield to hpa.

Fair enough.


Juergen

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#1374186 — Re: [PATCH v4 04/14] x86/rtc: replace paravirt rtc check with platform legacy quirk

On 04/08/2016 03:59 AM, Juergen Gross wrote:
> On 08/04/16 09:36, Luis R. Rodriguez wrote:
>> On Fri, Apr 8, 2016 at 12:13 AM, Juergen Gross <jgross@suse.com> wrote:
>>> On 08/04/16 08:56, Luis R. Rodriguez wrote:
>>>> On Thu, Apr 7, 2016 at 11:38 PM, Juergen Gross <jgross@suse.com> wrote:
>>>>
>>>> Okay. Another idea (not sure whether this is really a good one):
>>>>
>>>> Add X86_SUBARCH_XEN_DOM0. As hardware_subarch is 32 bits wide I don't
>>>> think the number of subarchs is a scarce resource. :-)
>> This would mean bumping the x86 boot protocol, we shouldn't take that
>> lightly, but given that in this case the new subarch would really only
>> be set by the kernel (or future loaders for perhaps HVMLite) I'd think
>> this is not such an intrusive alternative.
> I think adding an own subarch for dom0 isn't that bad. It really is
> different from domU as dom0 has per default access to the real hardware
> (or at least to most of it).

Can we do this (overwrite quirks) in x86_init_ops.arch_setup? I'd really 
like to avoid adding a what essentially is a sub-subarch.

-boris

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#1374416 — Re: [PATCH v4 04/14] x86/rtc: replace paravirt rtc check with platform legacy quirk

On Fri, Apr 08, 2016 at 08:37:44AM -0400, Boris Ostrovsky wrote:
> On 04/08/2016 03:59 AM, Juergen Gross wrote:
> >On 08/04/16 09:36, Luis R. Rodriguez wrote:
> >>On Fri, Apr 8, 2016 at 12:13 AM, Juergen Gross <jgross@suse.com> wrote:
> >>>On 08/04/16 08:56, Luis R. Rodriguez wrote:
> >>>>On Thu, Apr 7, 2016 at 11:38 PM, Juergen Gross <jgross@suse.com> wrote:
> >>>>
> >>>>Okay. Another idea (not sure whether this is really a good one):
> >>>>
> >>>>Add X86_SUBARCH_XEN_DOM0. As hardware_subarch is 32 bits wide I don't
> >>>>think the number of subarchs is a scarce resource. :-)
> >>This would mean bumping the x86 boot protocol, we shouldn't take that
> >>lightly, but given that in this case the new subarch would really only
> >>be set by the kernel (or future loaders for perhaps HVMLite) I'd think
> >>this is not such an intrusive alternative.
> >I think adding an own subarch for dom0 isn't that bad. It really is
> >different from domU as dom0 has per default access to the real hardware
> >(or at least to most of it).
> 
> Can we do this (overwrite quirks) in x86_init_ops.arch_setup? I'd
> really like to avoid adding a what essentially is a sub-subarch.

I'm going with this. Will respin.

  Luis

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