The ABI is broken and we cannot support it properly. Turn it off. If this causes a meaningful performance regression for someone, KVM can introduce an improved ABI that is supportable. Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx> --- arch/x86/kernel/kvm.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index 93ab0cbd304e..71f9f39f93da 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -318,11 +318,16 @@ static void kvm_guest_cpu_init(void) pa = slow_virt_to_phys(this_cpu_ptr(&apf_reason)); -#ifdef CONFIG_PREEMPTION - pa |= KVM_ASYNC_PF_SEND_ALWAYS; -#endif pa |= KVM_ASYNC_PF_ENABLED; + /* + * We do not set KVM_ASYNC_PF_SEND_ALWAYS. With the current + * KVM paravirt ABI, if an async page fault occurs on an early + * memory access in the normal (sync) #PF path or in an NMI + * that happens early in the #PF code, the combination of CR2 + * and the APF reason field will be corrupted. + */ + if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF_VMEXIT)) pa |= KVM_ASYNC_PF_DELIVERY_AS_PF_VMEXIT; -- 2.24.1
