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authorRadim Krčmář <rkrcmar@redhat.com>2018-02-01 22:16:21 +0100
committerPaolo Bonzini <pbonzini@redhat.com>2018-02-24 01:43:48 +0100
commitfe2a3027e74e40a3ece3a4c1e4e51403090a907a (patch)
tree1f69d431c10dd68c11f429d2cac9af9cea3bb490 /arch/x86/kernel/kvm.c
parentf75e4924f0152be747bf04c9d16bb23fd8baf5f9 (diff)
KVM: x86: fix backward migration with async_PF
Guests on new hypersiors might set KVM_ASYNC_PF_DELIVERY_AS_PF_VMEXIT bit when enabling async_PF, but this bit is reserved on old hypervisors, which results in a failure upon migration. To avoid breaking different cases, we are checking for CPUID feature bit before enabling the feature and nothing else. Fixes: 52a5c155cf79 ("KVM: async_pf: Let guest support delivery of async_pf from guest mode") Cc: <stable@vger.kernel.org> Reviewed-by: Wanpeng Li <wanpengli@tencent.com> Reviewed-by: David Hildenbrand <david@redhat.com> Signed-off-by: Radim Krčmář <rkrcmar@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/kernel/kvm.c')
-rw-r--r--arch/x86/kernel/kvm.c8
1 files changed, 4 insertions, 4 deletions
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 4e37d1a851a6..971babe964d2 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -341,10 +341,10 @@ static void kvm_guest_cpu_init(void)
#endif
pa |= KVM_ASYNC_PF_ENABLED;
- /* Async page fault support for L1 hypervisor is optional */
- if (wrmsr_safe(MSR_KVM_ASYNC_PF_EN,
- (pa | KVM_ASYNC_PF_DELIVERY_AS_PF_VMEXIT) & 0xffffffff, pa >> 32) < 0)
- wrmsrl(MSR_KVM_ASYNC_PF_EN, pa);
+ if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF_VMEXIT))
+ pa |= KVM_ASYNC_PF_DELIVERY_AS_PF_VMEXIT;
+
+ wrmsrl(MSR_KVM_ASYNC_PF_EN, pa);
__this_cpu_write(apf_reason.enabled, 1);
printk(KERN_INFO"KVM setup async PF for cpu %d\n",
smp_processor_id());