From: Ingo Molnar Date: Mon, 12 May 2008 19:21:15 +0000 (+0200) Subject: x86: prevent PGE flush from interruption/preemption X-Git-Tag: v2.6.26-rc4~11^2 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b1979a5fda7869a790f4fd83fb06c78498d26ba1;p=linux-2.6 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 Signed-off-by: Thomas Gleixner --- diff --git a/include/asm-x86/tlbflush.h b/include/asm-x86/tlbflush.h index 0c0674d942..35c76ceb9f 100644 --- a/include/asm-x86/tlbflush.h +++ b/include/asm-x86/tlbflush.h @@ -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)