Avi Kivity wrote: > On 03/17/2010 09:45 AM, Jan Kiszka wrote: >> Avi Kivity wrote: >> >>> Once upon a time, locked operations were emulated while holding the >>> mmu mutex. >>> Since mmu pages were write protected, it was safe to emulate the >>> writes in >>> a non-atomic manner, since there could be no other writer, either in the >>> guest or in the kernel. >>> >>> These days emulation takes place without holding the mmu spinlock, so >>> the >>> write could be preempted by an unshadowing event, which exposes the page >>> to writes by the guest. This may cause corruption of guest page tables. >>> >>> Fix by using an atomic cmpxchg for these operations. >>> >>> Signed-off-by: Avi Kivity<avi@xxxxxxxxxx> >>> --- >>> arch/x86/kvm/x86.c | 69 >>> ++++++++++++++++++++++++++++++++++++---------------- >>> 1 files changed, 48 insertions(+), 21 deletions(-) >>> >>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c >>> index 9d02cc7..d724a52 100644 >>> --- a/arch/x86/kvm/x86.c >>> +++ b/arch/x86/kvm/x86.c >>> @@ -3299,41 +3299,68 @@ int emulator_write_emulated(unsigned long addr, >>> } >>> EXPORT_SYMBOL_GPL(emulator_write_emulated); >>> >>> +#define CMPXCHG_TYPE(t, ptr, old, new) \ >>> + (cmpxchg((t *)(ptr), *(t *)(old), *(t *)(new)) == *(t *)(old)) >>> + >>> +#ifdef CONFIG_X86_64 >>> +# define CMPXCHG64(ptr, old, new) CMPXCHG_TYPE(u64, ptr, old, new) >>> +#else >>> +# define CMPXCHG64(ptr, old, new) \ >>> + (cmpxchg64((u64 *)(ptr), *(u64 *)(old), *(u *)(new)) == *(u64 >>> *)(old)) >>> >> ^^^^^^ >> This should cause the 32-bit build breakage I see with the current next >> branch. >> > > Also, Marcelo sees autotest breakage, so it's also broken on 64-bit > somehow. > Obviously, the 64-bit case is considered stable now and 32 bit remained untested (not included in autotest?). So here is the build fix: ----------> KVM: x86: Fix 32-bit build breakage due to typo Signed-off-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx> --- arch/x86/kvm/x86.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index bb9a24a..097ad3a 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -3322,7 +3322,7 @@ EXPORT_SYMBOL_GPL(emulator_write_emulated); # define CMPXCHG64(ptr, old, new) CMPXCHG_TYPE(u64, ptr, old, new) #else # define CMPXCHG64(ptr, old, new) \ - (cmpxchg64((u64 *)(ptr), *(u64 *)(old), *(u *)(new)) == *(u64 *)(old)) + (cmpxchg64((u64 *)(ptr), *(u64 *)(old), *(u64 *)(new)) == *(u64 *)(old)) #endif static int emulator_cmpxchg_emulated(unsigned long addr, -- 1.6.0.2
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