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x86: prevent PGE flush from interruption/preemption 

CR4 manipulation is not protected against interrupts and preemption,
but KVM uses smp_function_call to manipulate the X86_CR4_VMXE bit
either from the CPU hotplug code or from the kvm_init call.

We need to protect the CR4 manipulation from both interrupts and
preemption.

Original bug report: http://lkml.org/lkml/2008/5/7/48
Bugzilla entry: http://bugzilla.kernel.org/show_bug.cgi?id=10642

This is not a regression from 2.6.25, it's a long standing and hard to
trigger bug.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Ingo Molnar 2008-05-12 21:21:15 +02:00 committed by Thomas Gleixner
parent a1289643ad
commit b1979a5fda
1 changed files with 12 additions and 1 deletions
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13
include/asm-x86/tlbflush.h
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@ -22,12 +22,23 @@ static inline void __native_flush_tlb(void)
static inline void __native_flush_tlb_global(void)
{
unsigned long cr4 = read_cr4();
unsigned long flags;
unsigned long cr4;
/*
* Read-modify-write to CR4 - protect it from preemption and
* from interrupts. (Use the raw variant because this code can
* be called from deep inside debugging code.)
*/
raw_local_irq_save(flags);
cr4 = read_cr4();
/* clear PGE */
write_cr4(cr4 & ~X86_CR4_PGE);
/* write old PGE again and flush TLBs */
write_cr4(cr4);
raw_local_irq_restore(flags);
}
static inline void __native_flush_tlb_single(unsigned long addr)