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Groups > linux.kernel > #1363690

[PATCH v3 6/7] x86/xen,pat: Remove PAT table init code from Xen

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Xen supports PAT without MTRRs for its guests.  In order to
enable WC attribute, it was necessary for xen_start_kernel()
to call pat_init_cache_modes() to update PAT table before
starting guest kernel.

Now that the kernel initializes PAT table to the BIOS handoff
state when MTRR is disabled, this Xen-specific PAT init code
is no longer necessary.  Delete it from xen_start_kernel().

Also change __init_cache_modes() to a static function since
PAT table should not be tweaked by other modules.

Signed-off-by: Toshi Kani <toshi.kani@hpe.com>
Acked-by: Juergen Gross <jgross@suse.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Luis R. Rodriguez <mcgrof@suse.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
---
 arch/x86/include/asm/pat.h |    1 -
 arch/x86/mm/pat.c          |    2 +-
 arch/x86/xen/enlighten.c   |    9 ---------
 3 files changed, 1 insertion(+), 11 deletions(-)

diff --git a/arch/x86/include/asm/pat.h b/arch/x86/include/asm/pat.h
index 0ad356c..0b1ff4c 100644
--- a/arch/x86/include/asm/pat.h
+++ b/arch/x86/include/asm/pat.h
@@ -7,7 +7,6 @@
 bool pat_enabled(void);
 void pat_disable(const char *reason);
 extern void pat_init(void);
-void __init_cache_modes(u64);
 
 extern int reserve_memtype(u64 start, u64 end,
 		enum page_cache_mode req_pcm, enum page_cache_mode *ret_pcm);
diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 3aea1ab..9db6915 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -192,7 +192,7 @@ static enum page_cache_mode pat_get_cache_mode(unsigned pat_val, char *msg)
  * configuration.
  * Using lower indices is preferred, so we start with highest index.
  */
-void __init_cache_modes(u64 pat)
+static void __init_cache_modes(u64 pat)
 {
 	enum page_cache_mode cache;
 	char pat_msg[33];
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index f4296b6..d5f172d 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -75,7 +75,6 @@
 #include <asm/mach_traps.h>
 #include <asm/mwait.h>
 #include <asm/pci_x86.h>
-#include <asm/pat.h>
 #include <asm/cpu.h>
 
 #ifdef CONFIG_ACPI
@@ -1511,7 +1510,6 @@ asmlinkage __visible void __init xen_start_kernel(void)
 {
 	struct physdev_set_iopl set_iopl;
 	unsigned long initrd_start = 0;
-	u64 pat;
 	int rc;
 
 	if (!xen_start_info)
@@ -1618,13 +1616,6 @@ asmlinkage __visible void __init xen_start_kernel(void)
 				   xen_start_info->nr_pages);
 	xen_reserve_special_pages();
 
-	/*
-	 * Modify the cache mode translation tables to match Xen's PAT
-	 * configuration.
-	 */
-	rdmsrl(MSR_IA32_CR_PAT, pat);
-	__init_cache_modes(pat);
-
 	/* keep using Xen gdt for now; no urgent need to change it */
 
 #ifdef CONFIG_X86_32

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[PATCH v3 0/7] Enhance PAT init to fix Xorg crashes Toshi Kani <toshi.kani@hpe.com> - 2016-03-23 21:50 +0100
  [PATCH v3 1/7] x86/mm/pat: Add support of non-default PAT MSR setting Toshi Kani <toshi.kani@hpe.com> - 2016-03-23 21:50 +0100
    [tip:x86/mm] x86/mm/pat: Add support of non-default PAT MSR setting tip-bot for Toshi Kani <tipbot@zytor.com> - 2016-03-29 12:40 +0200
  [PATCH v3 5/7] x86/mtrr: Fix PAT init handling when MTRR is disabled Toshi Kani <toshi.kani@hpe.com> - 2016-03-23 22:00 +0100
    [tip:x86/mm] x86/mtrr: Fix PAT init handling when MTRR is disabled tip-bot for Toshi Kani <tipbot@zytor.com> - 2016-03-29 12:50 +0200
  [PATCH v3 6/7] x86/xen,pat: Remove PAT table init code from Xen Toshi Kani <toshi.kani@hpe.com> - 2016-03-23 22:00 +0100
    [tip:x86/mm] x86/xen, pat: Remove PAT table init code from Xen tip-bot for Toshi Kani <tipbot@zytor.com> - 2016-03-29 12:50 +0200
  [PATCH v3 3/7] x86/mm/pat: Replace cpu_has_pat with boot_cpu_has Toshi Kani <toshi.kani@hpe.com> - 2016-03-23 22:00 +0100
    [tip:x86/mm] x86/mm/pat: Replace cpu_has_pat with boot_cpu_has() tip-bot for Toshi Kani <tipbot@zytor.com> - 2016-03-29 12:50 +0200
  [PATCH v3 2/7] x86/mm/pat: Add pat_disable() interface Toshi Kani <toshi.kani@hpe.com> - 2016-03-23 22:00 +0100
    [tip:x86/mm] x86/mm/pat: Add pat_disable() interface tip-bot for Toshi Kani <tipbot@zytor.com> - 2016-03-29 12:50 +0200
  [PATCH v3 7/7] x86/pat: Document PAT initialization Toshi Kani <toshi.kani@hpe.com> - 2016-03-23 22:00 +0100
    [tip:x86/mm] x86/pat: Document the PAT initialization sequence tip-bot for Toshi Kani <tipbot@zytor.com> - 2016-03-29 12:50 +0200
  [PATCH v3 4/6] x86/mtrr: Fix Xorg crashes in Qemu sessions Toshi Kani <toshi.kani@hpe.com> - 2016-03-23 22:00 +0100
    [tip:x86/mm] x86/mtrr: Fix Xorg crashes in Qemu sessions tip-bot for Toshi Kani <tipbot@zytor.com> - 2016-03-29 12:50 +0200
  Re: [PATCH v3 0/7] Enhance PAT init to fix Xorg crashes Ingo Molnar <mingo@kernel.org> - 2016-03-29 12:40 +0200
    Re: [PATCH v3 0/7] Enhance PAT init to fix Xorg crashes Toshi Kani <toshi.kani@hpe.com> - 2016-03-29 15:30 +0200
      Re: [Xen-devel] [PATCH v3 0/7] Enhance PAT init to fix Xorg crashes Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-03-29 16:50 +0200
        Re: [Xen-devel] [PATCH v3 0/7] Enhance PAT init to fix Xorg crashes Toshi Kani <toshi.kani@hpe.com> - 2016-03-29 17:00 +0200
          Re: [Xen-devel] [PATCH v3 0/7] Enhance PAT init to fix Xorg crashes "Luis R. Rodriguez" <mcgrof@suse.com> - 2016-03-30 20:10 +0200
            Re: [LKP] [Xen-devel] [PATCH v3 0/7] Enhance PAT init to fix Xorg crashes "Luis R. Rodriguez" <mcgrof@suse.com> - 2016-03-30 22:20 +0200
              Re: [LKP] [Xen-devel] [PATCH v3 0/7] Enhance PAT init to fix Xorg crashes "Luis R. Rodriguez" <mcgrof@suse.com> - 2016-03-30 22:50 +0200

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