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x86/entry/32: Pull the MSR_IA32_SYSENTER_CS update code out of native_load_sp0()

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This causes the MSR_IA32_SYSENTER_CS write to move out of the
paravirt callback.  This shouldn't affect Xen PV: Xen already ignores
MSR_IA32_SYSENTER_ESP writes.  In any event, Xen doesn't support
vm86() in a useful way.

Note to any potential backporters: This patch won't break lguest, as
lguest didn't have any SYSENTER support at all.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bpetkov@suse.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/75cf09fe03ae778532d0ca6c65aa58e66bc2f90c.1509609304.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Andy Lutomirski
2017-11-02 00:59:09 -07:00
committed by Ingo Molnar
parent 929bacec21
commit bd7dc5a6af
5 changed files with 21 additions and 10 deletions
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12
arch/x86/include/asm/switch_to.h
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@@ -72,4 +72,16 @@ do { \
((last) = __switch_to_asm((prev), (next))); \
} while (0)
#ifdef CONFIG_X86_32
static inline void refresh_sysenter_cs(struct thread_struct *thread)
{
/* Only happens when SEP is enabled, no need to test "SEP"arately: */
if (unlikely(this_cpu_read(cpu_tss.x86_tss.ss1) == thread->sysenter_cs))
return;
this_cpu_write(cpu_tss.x86_tss.ss1, thread->sysenter_cs);
wrmsr(MSR_IA32_SYSENTER_CS, thread->sysenter_cs, 0);
}
#endif
#endif /* _ASM_X86_SWITCH_TO_H */