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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 /Documentation
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 'Documentation')
-rw-r--r--Documentation/virtual/kvm/cpuid.txt4
-rw-r--r--Documentation/virtual/kvm/msr.txt3
2 files changed, 6 insertions, 1 deletions
diff --git a/Documentation/virtual/kvm/cpuid.txt b/Documentation/virtual/kvm/cpuid.txt
index dcab6dc11e3b..87a7506f31c2 100644
--- a/Documentation/virtual/kvm/cpuid.txt
+++ b/Documentation/virtual/kvm/cpuid.txt
@@ -58,6 +58,10 @@ KVM_FEATURE_PV_TLB_FLUSH || 9 || guest checks this feature bit
|| || before enabling paravirtualized
|| || tlb flush.
------------------------------------------------------------------------------
+KVM_FEATURE_ASYNC_PF_VMEXIT || 10 || paravirtualized async PF VM exit
+ || || can be enabled by setting bit 2
+ || || when writing to msr 0x4b564d02
+------------------------------------------------------------------------------
KVM_FEATURE_CLOCKSOURCE_STABLE_BIT || 24 || host will warn if no guest-side
|| || per-cpu warps are expected in
|| || kvmclock.
diff --git a/Documentation/virtual/kvm/msr.txt b/Documentation/virtual/kvm/msr.txt
index 1ebecc115dc6..f3f0d57ced8e 100644
--- a/Documentation/virtual/kvm/msr.txt
+++ b/Documentation/virtual/kvm/msr.txt
@@ -170,7 +170,8 @@ MSR_KVM_ASYNC_PF_EN: 0x4b564d02
when asynchronous page faults are enabled on the vcpu 0 when
disabled. Bit 1 is 1 if asynchronous page faults can be injected
when vcpu is in cpl == 0. Bit 2 is 1 if asynchronous page faults
- are delivered to L1 as #PF vmexits.
+ are delivered to L1 as #PF vmexits. Bit 2 can be set only if
+ KVM_FEATURE_ASYNC_PF_VMEXIT is present in CPUID.
First 4 byte of 64 byte memory location will be written to by
the hypervisor at the time of asynchronous page fault (APF)