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Commit 0c752a93 authored by Suresh Siddha's avatar Suresh Siddha Committed by H. Peter Anvin
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x86: introduce noxsave boot parameter 



Introduce "noxsave" boot parameter which will disable the cpu's xsave/xrstor
capabilities. Useful for debugging and working around xsave related issues.

[ Impact: make it possible to debug problems in the field ]

Signed-off-by: default avatarSuresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: default avatarH. Peter Anvin <hpa@zytor.com>
parent bca23dba

Documentation/kernel-parameters.txt

+4 −0
Original line number Diff line number Diff line
@@ -1535,6 +1535,10 @@ and is between 256 and 4096 characters. It is defined in the file 
			register save and restore. The kernel will only save

			legacy floating-point registers on task switch.



	noxsave		[BUGS=X86] Disables x86 extended register state save

			and restore using xsave. The kernel will fallback to

			enabling legacy floating-point and sse state.



	nohlt		[BUGS=ARM,SH] Tells the kernel that the sleep(SH) or

			wfi(ARM) instruction doesn't work correctly and not to

			use it. This is also useful when using JTAG debugger.

arch/x86/kernel/cpu/common.c

+7 −0
Original line number Diff line number Diff line
@@ -114,6 +114,13 @@ DEFINE_PER_CPU_PAGE_ALIGNED(struct gdt_page, gdt_page) = { .gdt = { 
} };

EXPORT_PER_CPU_SYMBOL_GPL(gdt_page);



static int __init x86_xsave_setup(char *s)

{

	setup_clear_cpu_cap(X86_FEATURE_XSAVE);

	return 1;

}

__setup("noxsave", x86_xsave_setup);



#ifdef CONFIG_X86_32

static int cachesize_override __cpuinitdata = -1;

static int disable_x86_serial_nr __cpuinitdata = 1;