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Commit b6f42a4a authored by Fenghua Yu's avatar Fenghua Yu Committed by H. Peter Anvin
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x86/xsaves: Add a kernel parameter noxsaves to disable xsaves/xrstors 



This patch adds a kernel parameter noxsaves to disable xsaves/xrstors feature.
The kernel will fall back to use xsaveopt and xrstor to save and restor
xstates. By using this parameter, xsave area occupies more memory because
standard form of xsave area in xsaveopt/xrstor occupies more memory than
compacted form of xsave area.

This patch adds a description of the kernel parameter noxsaveopt in doc.
The code to support the parameter noxsaveopt has been in the kernel before.
This patch just adds the description of this parameter in the doc.

Signed-off-by: default avatarFenghua Yu <fenghua.yu@intel.com>
Link: http://lkml.kernel.org/r/1401387164-43416-4-git-send-email-fenghua.yu@intel.com


Signed-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
parent 6229ad27

Documentation/kernel-parameters.txt

+15 −0
Original line number Diff line number Diff line
@@ -2124,6 +2124,21 @@ bytes respectively. Such letter suffixes can also be entirely omitted. 
			and restore using xsave. The kernel will fallback to

			enabling legacy floating-point and sse state.



	noxsaveopt	[X86] Disables xsaveopt used in saving x86 extended

			register states. The kernel will fall back to use

			xsave to save the states. By using this parameter,

			performance of saving the states is degraded because

			xsave doesn't support modified optimization while

			xsaveopt supports it on xsaveopt enabled systems.



	noxsaves	[X86] Disables xsaves and xrstors used in saving and

			restoring x86 extended register state in compacted

			form of xsave area. The kernel will fall back to use

			xsaveopt and xrstor to save and restore the states

			in standard form of xsave area. By using this

			parameter, xsave area per process might occupy more

			memory on xsaves enabled systems.



	eagerfpu=	[X86]

			on	enable eager fpu restore

			off	disable eager fpu restore

arch/x86/kernel/cpu/common.c

+8 −0
Original line number Diff line number Diff line
@@ -146,6 +146,7 @@ static int __init x86_xsave_setup(char *s) 
{

	setup_clear_cpu_cap(X86_FEATURE_XSAVE);

	setup_clear_cpu_cap(X86_FEATURE_XSAVEOPT);

	setup_clear_cpu_cap(X86_FEATURE_XSAVES);

	setup_clear_cpu_cap(X86_FEATURE_AVX);

	setup_clear_cpu_cap(X86_FEATURE_AVX2);

	return 1;
@@ -159,6 +160,13 @@ static int __init x86_xsaveopt_setup(char *s) 
}

__setup("noxsaveopt", x86_xsaveopt_setup);



static int __init x86_xsaves_setup(char *s)

{

	setup_clear_cpu_cap(X86_FEATURE_XSAVES);

	return 1;

}

__setup("noxsaves", x86_xsaves_setup);



#ifdef CONFIG_X86_32

static int cachesize_override = -1;

static int disable_x86_serial_nr = 1;