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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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6
arch/x86/kernel/vm86_32.c
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@@ -54,6 +54,7 @@
#include <asm/irq.h>
#include <asm/traps.h>
#include <asm/vm86.h>
#include <asm/switch_to.h>
/*
* Known problems:
@@ -149,6 +150,7 @@ void save_v86_state(struct kernel_vm86_regs *regs, int retval)
tsk->thread.sp0 = vm86->saved_sp0;
tsk->thread.sysenter_cs = __KERNEL_CS;
load_sp0(tss, &tsk->thread);
refresh_sysenter_cs(&tsk->thread);
vm86->saved_sp0 = 0;
put_cpu();
@@ -368,8 +370,10 @@ static long do_sys_vm86(struct vm86plus_struct __user *user_vm86, bool plus)
/* make room for real-mode segments */
tsk->thread.sp0 += 16;
if (static_cpu_has(X86_FEATURE_SEP))
if (static_cpu_has(X86_FEATURE_SEP)) {
tsk->thread.sysenter_cs = 0;
refresh_sysenter_cs(&tsk->thread);
}
load_sp0(tss, &tsk->thread);
put_cpu();