Re: [PATCH v5 2/4] KVM: async_pf: Add L1 guest async_pf #PF vmexit handler

[Wanpeng Li <kernellwp@gmail.com>]

2017-06-27 21:30 GMT+08:00 Paolo Bonzini <pbonzini@redhat.com>:
>
>
> On 27/06/2017 03:46, Wanpeng Li wrote:
>> From: Wanpeng Li <wanpeng.li@hotmail.com>
>>
>> This patch adds the L1 guest async page fault #PF vmexit handler, such
>> #PF is converted into vmexit from L2 to L1 on #PF which is then handled
>> by L1 similar to ordinary async page fault.
>>
>> Cc: Paolo Bonzini <pbonzini@redhat.com>
>> Cc: Radim Krčmář <rkrcmar@redhat.com>
>> Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
>> ---
>>  arch/x86/kvm/vmx.c | 34 ++++++++++++++++++++++++++++------
>>  1 file changed, 28 insertions(+), 6 deletions(-)
>>
>> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
>> index df825bb..f533cc1 100644
>> --- a/arch/x86/kvm/vmx.c
>> +++ b/arch/x86/kvm/vmx.c
>> @@ -616,6 +616,7 @@ struct vcpu_vmx {
>>       bool emulation_required;
>>
>>       u32 exit_reason;
>> +     u32 apf_reason;
>
> Can you instead of move vcpu_svm's apf_reason field to kvm_vcpu_arch?
> (e.g. vcpu->arch.apf.host_apf_reason)?

Agreed.

>
>>       /* Posted interrupt descriptor */
>>       struct pi_desc pi_desc;
>> @@ -5648,14 +5649,31 @@ static int handle_exception(struct kvm_vcpu *vcpu)
>>       }
>>
>>       if (is_page_fault(intr_info)) {
>> -             /* EPT won't cause page fault directly */
>> -             BUG_ON(enable_ept);
>>               cr2 = vmcs_readl(EXIT_QUALIFICATION);
>> -             trace_kvm_page_fault(cr2, error_code);
>> +             switch (vmx->apf_reason) {
>> +             default:
>> +                     /* EPT won't cause page fault directly */
>> +                     BUG_ON(enable_ept);
>> +                     trace_kvm_page_fault(cr2, error_code);
>>
>> -             if (kvm_event_needs_reinjection(vcpu))
>> -                     kvm_mmu_unprotect_page_virt(vcpu, cr2);
>> -             return kvm_mmu_page_fault(vcpu, cr2, error_code, NULL, 0);
>> +                     if (kvm_event_needs_reinjection(vcpu))
>> +                             kvm_mmu_unprotect_page_virt(vcpu, cr2);
>> +                     return kvm_mmu_page_fault(vcpu, cr2, error_code, NULL, 0);
>> +                     break;
>> +             case KVM_PV_REASON_PAGE_NOT_PRESENT:
>> +                     vmx->apf_reason = 0;
>> +                     local_irq_disable();
>> +                     kvm_async_pf_task_wait(cr2);
>> +                     local_irq_enable();
>> +                     break;
>> +             case KVM_PV_REASON_PAGE_READY:
>> +                     vmx->apf_reason = 0;
>> +                     local_irq_disable();
>> +                     kvm_async_pf_task_wake(cr2);
>> +                     local_irq_enable();
>> +                     break;
>> +             }
>> +             return 0;
>>       }
>
>
> This code can be moved to a common function
>
>         int kvm_handle_page_fault(struct kvm_vcpu *vcpu, u64 error_code,
>                                   u64 fault_address);
>
> in mmu.c.  It can be used by vmx.c here and in svm.c's pf_interception.
>
> You can change "enable_ept" to "tdp_enabled" (but please make that a
> WARN_ON_ONCE, too).

Agreed. :)

Regards,
Wanpeng Li