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[PATCH v6 06/16] x86/init: use a platform legacy quirk for ebda

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

As per 0-day, this bumps the vmlinux size using i386-tinyconfig as
follows:

TOTAL   TEXT   init.text   x86_early_init_platform_quirks()
+39     +35    +35         +25

That's a 4 byte total overhead, the rest is all cleared out
upon init as its all __init text.

v2: document 0-day vmlinux size impact

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 8bb8c1a4615a..89d9d57e145d 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 021a5f973ce3..01b159781d96 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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[PATCH v6 00/16] x86: remove paravirt_enabled() "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-04-14 02:10 +0200
  [PATCH v6 06/16] x86/init: use a platform legacy quirk for ebda "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-04-14 02:10 +0200
  [PATCH v6 12/16] x86, ACPI: parse ACPI_FADT_LEGACY_DEVICES "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-04-14 02:10 +0200
  [PATCH v6 11/16] pnpbios: replace paravirt_enabled() check with legacy device check "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-04-14 02:10 +0200
  [PATCH v6 08/16] apm32: remove paravirt_enabled() use "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-04-14 02:10 +0200
  [PATCH v6 07/16] tools/lguest: force disable tboot and apm "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-04-14 02:10 +0200
  [PATCH v6 03/16] tools/lguest: make lguest launcher use X86_SUBARCH_LGUEST explicitly "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-04-14 02:10 +0200
  [PATCH v6 01/16] x86/boot: enumerate documentation for the x86 hardware_subarch "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-04-14 02:10 +0200
  [PATCH v6 16/16] x86/init: disable pnpbios and rtc for X86_SUBARCH_CE4100 "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-04-14 02:10 +0200
  [PATCH v6 10/16] x86/cpu/intel: remove not needed paravirt_enabled() for f00f work around "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-04-14 02:10 +0200
  [PATCH v6 14/16] x86/paravirt: remove paravirt_enabled() "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-04-14 02:10 +0200
  [PATCH v6 15/16] x86/init: disable pnpbios for X86_SUBARCH_INTEL_MID "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-04-14 02:10 +0200
  [PATCH v6 13/16] x86/init: rename ebda code file "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-04-14 02:10 +0200
  [PATCH v6 04/16] x86/rtc: replace paravirt rtc check with platform legacy quirk "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-04-14 02:10 +0200
    Re: [PATCH v6 04/16] x86/rtc: replace paravirt rtc check with  platform legacy quirk Juergen Gross <jgross@suse.com> - 2016-04-14 06:30 +0200
  [PATCH v6 07/16] tools/lguest: force disable tboot and apm "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-04-14 02:20 +0200
  [PATCH v6 05/16] x86, ACPI: move ACPI_FADT_NO_CMOS_RTC check to ACPI boot code "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-04-14 02:20 +0200
  [PATCH v6 12/16] x86, ACPI: parse ACPI_FADT_LEGACY_DEVICES "Luis R. Rodriguez" <mcgrof@kernel.org> - 2016-04-14 02:20 +0200

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