On Fri, Mar 9, 2018 at 3:43 PM, Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:
> On 09/03/2018 14:20, Jack Wang wrote:
>> From: Radim Krčmář <rkrcmar@xxxxxxxxxx>
>>
>> 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@xxxxxxxxxxxxxxx>
>> Reviewed-by: Wanpeng Li <wanpengli@xxxxxxxxxxx>
>> Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
>> Signed-off-by: Radim Krčmář <rkrcmar@xxxxxxxxxx>
>> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
>> [jwang: port to 4.14]
>> Signed-off-by: Jack Wang <jinpu.wang@xxxxxxxxxxxxxxxx>
>> ---
>> Documentation/virtual/kvm/cpuid.txt | 4 ++++
>> Documentation/virtual/kvm/msr.txt | 3 ++-
>> arch/x86/include/uapi/asm/kvm_para.h | 1 +
>> arch/x86/kernel/kvm.c | 8 ++++----
>> arch/x86/kvm/cpuid.c | 3 ++-
>> 5 files changed, 13 insertions(+), 6 deletions(-)
>>
>> diff --git a/Documentation/virtual/kvm/cpuid.txt b/Documentation/virtual/kvm/cpuid.txt
>> index 3c65feb..a81c97a 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 1ebecc1..f3f0d57 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 09cc064..989db88 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 b40ffbf..0a93e83b 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 13f5d42..4f544f2 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);
>>
>
> Acked-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
>
> Thanks Jack!
>
> Paolo
Thanks Paolo!
Jack