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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>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: andrew.cooper3@citrix.com
Cc: andriy.shevchenko@linux.intel.com
Cc: bigeasy@linutronix.de
Cc: boris.ostrovsky@oracle.com
Cc: david.vrabel@citrix.com
Cc: ffainelli@freebox.fr
Cc: george.dunlap@citrix.com
Cc: glin@suse.com
Cc: jgross@suse.com
Cc: jlee@suse.com
Cc: josh@joshtriplett.org
Cc: julien.grall@linaro.org
Cc: konrad.wilk@oracle.com
Cc: kozerkov@parallels.com
Cc: lenb@kernel.org
Cc: lguest@lists.ozlabs.org
Cc: linux-acpi@vger.kernel.org
Cc: lv.zheng@intel.com
Cc: matt@codeblueprint.co.uk
Cc: mbizon@freebox.fr
Cc: rjw@rjwysocki.net
Cc: robert.moore@intel.com
Cc: rusty@rustcorp.com.au
Cc: tiwai@suse.de
Cc: toshi.kani@hp.com
Cc: xen-devel@lists.xensource.com
Link: http://lkml.kernel.org/r/1460592286-300-7-git-send-email-mcgrof@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Luis R. Rodriguez 2016-04-13 17:04:36 -07:00 committed by Ingo Molnar
parent 088a8ef820
commit 1330e3bc54
3 changed files with 8 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
arch/x86/include/asm/x86_init.h
View File

@ -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;
};
/**

2
arch/x86/kernel/head.c
View File

@ -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 */

4
arch/x86/kernel/platform-quirks.c
View File

@ -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: