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authorRadim Krčmář <rkrcmar@redhat.com>2018-02-01 22:16:21 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-03-11 16:23:23 +0100
commitdc6fb79de47daa1cb38054af318ff6725eb473cc (patch)
tree3c460bcf947207616162420286d1195c8d66cd16
parenta91064ff43a26357c91be2c77f420a78dce6a19a (diff)
KVM: x86: fix backward migration with async_PF
commit fe2a3027e74e40a3ece3a4c1e4e51403090a907a upstream. 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> [jwang: port to 4.14] Signed-off-by: Jack Wang <jinpu.wang@profitbricks.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--Documentation/virtual/kvm/cpuid.txt4
-rw-r--r--Documentation/virtual/kvm/msr.txt3
-rw-r--r--arch/x86/include/uapi/asm/kvm_para.h1
-rw-r--r--arch/x86/kernel/kvm.c8
-rw-r--r--arch/x86/kvm/cpuid.c3
5 files changed, 13 insertions, 6 deletions
diff --git a/Documentation/virtual/kvm/cpuid.txt b/Documentation/virtual/kvm/cpuid.txt
index 3c65feb83010..a81c97a4b4a5 100644
--- a/Documentation/virtual/kvm/cpuid.txt
+++ b/Documentation/virtual/kvm/cpuid.txt
@@ -54,6 +54,10 @@ KVM_FEATURE_PV_UNHALT || 7 || guest checks this feature bit
|| || before enabling paravirtualized
|| || spinlock support.
------------------------------------------------------------------------------
+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)
diff --git a/arch/x86/include/uapi/asm/kvm_para.h b/arch/x86/include/uapi/asm/kvm_para.h
index 554aa8f24f91..341db0462b85 100644
--- a/arch/x86/include/uapi/asm/kvm_para.h
+++ b/arch/x86/include/uapi/asm/kvm_para.h
@@ -25,6 +25,7 @@
#define KVM_FEATURE_STEAL_TIME 5
#define KVM_FEATURE_PV_EOI 6
#define KVM_FEATURE_PV_UNHALT 7
+#define KVM_FEATURE_ASYNC_PF_VMEXIT 10
/* The last 8 bits are used to indicate how to interpret the flags field
* in pvclock structure. If no bits are set, all flags are ignored.
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index a94de09edbed..652bdd867782 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());
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 13f5d4217e4f..4f544f2a7b06 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -597,7 +597,8 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
(1 << KVM_FEATURE_ASYNC_PF) |
(1 << KVM_FEATURE_PV_EOI) |
(1 << KVM_FEATURE_CLOCKSOURCE_STABLE_BIT) |
- (1 << KVM_FEATURE_PV_UNHALT);
+ (1 << KVM_FEATURE_PV_UNHALT) |
+ (1 << KVM_FEATURE_ASYNC_PF_VMEXIT);
if (sched_info_on())
entry->eax |= (1 << KVM_FEATURE_STEAL_TIME);