x86/entry/32: Pull the MSR_IA32_SYSENTER_CS update code out of native_load_sp0()
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>
diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index 1196625..0936ed3 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -284,9 +284,11 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
/*
* Reload esp0 and cpu_current_top_of_stack. This changes
- * current_thread_info().
+ * current_thread_info(). Refresh the SYSENTER configuration in
+ * case prev or next is vm86.
*/
load_sp0(tss, next);
+ refresh_sysenter_cs(next);
this_cpu_write(cpu_current_top_of_stack,
(unsigned long)task_stack_page(next_p) +
THREAD_SIZE);
