Commit b1979a5f authored May 12, 2008 by Ingo Molnar Committed by Thomas Gleixner May 23, 2008

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>

parent a1289643

include/asm-x86/tlbflush.h

+12 −1

Original line number	Diff line number	Diff line
		@@ -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)

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