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x86/xsaves: Add a kernel parameter noxsaves to disable xsaves/xrstors

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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: Fenghua Yu <fenghua.yu@intel.com>
Link: http://lkml.kernel.org/r/1401387164-43416-4-git-send-email-fenghua.yu@intel.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
This commit is contained in:
Fenghua Yu 2014-05-29 11:12:31 -07:00 committed by H. Peter Anvin
parent 6229ad278c
commit b6f42a4a3c
2 changed files with 23 additions and 0 deletions
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15
Documentation/kernel-parameters.txt
View file

@ -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

8
arch/x86/kernel/cpu/common.c
View file

@ -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;