linux-kernel - Re: [PATCH v7 2/4] KVM: async_pf: Add L1 guest async

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Date:   Fri, 14 Jul 2017 09:40:03 +0800
From:   Wanpeng Li <kernellwp@...il.com>
To:     Radim Krčmář <rkrcmar@...hat.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        kvm <kvm@...r.kernel.org>, Paolo Bonzini <pbonzini@...hat.com>,
        Wanpeng Li <wanpeng.li@...mail.com>
Subject: Re: [PATCH v7 2/4] KVM: async_pf: Add L1 guest async_pf #PF vmexit handler

2017-07-13 23:29 GMT+08:00 Radim Krčmář <rkrcmar@...hat.com>:
> 2017-07-12 23:44+0200, Radim Krčmář:
>> 2017-06-28 20:01-0700, Wanpeng Li:
>> > From: Wanpeng Li <wanpeng.li@...mail.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@...hat.com>
>> > Cc: Radim Krčmář <rkrcmar@...hat.com>
>> > Signed-off-by: Wanpeng Li <wanpeng.li@...mail.com>
>> > ---
>>
>> This patch breaks SVM, so I've taken the series off kvm/queue for now;
>
> The error is triggered by 'WARN_ON_ONCE(tdp_enabled);', because
> pf_interception() handles both cases.  (The bizzare part is that it
> doesn't warn.)
>
> I think this hunk on top of the patch would be good.  It makes the

Thanks Radim! The work is really appreciated. :)

> WARN_ON_ONCE specific to VMX and also preserves the parameters that SVM
> had before.

I replace the tdp_enabled by enable_ept in VMX since there is a
warning: "tdp_enabled" in [kvm-intel.ko] undefined! Btw, I just sent
out v8, hope both
the v8 and vm86 stuff can catch the end of the merge window. :)

Regards,
Wanpeng Li

>
> (Passes basic tests, haven't done the nested async_pf test yet.)
>
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index f37c0307dcb0..338cb4c8cbb9 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -3782,17 +3782,16 @@ static bool try_async_pf(struct kvm_vcpu *vcpu, bool prefault, gfn_t gfn,
>  }
>
>  int kvm_handle_page_fault(struct kvm_vcpu *vcpu, u64 error_code,
> -                               u64 fault_address)
> +                               u64 fault_address, char *insn, int insn_len,
> +                               bool need_unprotect)
>  {
>         int r = 1;
>
>         switch (vcpu->arch.apf.host_apf_reason) {
>         default:
> -               /* TDP won't cause page fault directly */
> -               WARN_ON_ONCE(tdp_enabled);
>                 trace_kvm_page_fault(fault_address, error_code);
>
> -               if (kvm_event_needs_reinjection(vcpu))
> +               if (need_unprotect && kvm_event_needs_reinjection(vcpu))
>                         kvm_mmu_unprotect_page_virt(vcpu, fault_address);
>                 r = kvm_mmu_page_fault(vcpu, fault_address, error_code, NULL, 0);
>                 break;
> diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
> index 270d9adaa039..d7d248a000dd 100644
> --- a/arch/x86/kvm/mmu.h
> +++ b/arch/x86/kvm/mmu.h
> @@ -78,7 +78,8 @@ void kvm_init_shadow_ept_mmu(struct kvm_vcpu *vcpu, bool execonly,
>                              bool accessed_dirty);
>  bool kvm_can_do_async_pf(struct kvm_vcpu *vcpu);
>  int kvm_handle_page_fault(struct kvm_vcpu *vcpu, u64 error_code,
> -                               u64 fault_address);
> +                               u64 fault_address, char *insn, int insn_len,
> +                               bool need_unprotect);
>
>  static inline unsigned int kvm_mmu_available_pages(struct kvm *kvm)
>  {
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index 659b610c4711..fb23497cf915 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -2123,7 +2123,9 @@ static int pf_interception(struct vcpu_svm *svm)
>         u64 fault_address = svm->vmcb->control.exit_info_2;
>         u64 error_code = svm->vmcb->control.exit_info_1;
>
> -       return kvm_handle_page_fault(&svm->vcpu, error_code, fault_address);
> +       return kvm_handle_page_fault(&svm->vcpu, error_code, fault_address,
> +                       svm->vmcb->control.insn_bytes,
> +                       svm->vmcb->control.insn_len, !npt_enabled);
>  }
>
>  static int db_interception(struct vcpu_svm *svm)
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index ab33eace4f66..2e8cfb2f1371 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -5699,7 +5699,10 @@ static int handle_exception(struct kvm_vcpu *vcpu)
>
>         if (is_page_fault(intr_info)) {
>                 cr2 = vmcs_readl(EXIT_QUALIFICATION);
> -               return kvm_handle_page_fault(vcpu, error_code, cr2);
> +               /* TDP won't cause page fault directly */
> +               WARN_ON_ONCE(!vcpu->arch.apf.host_apf_reason && tdp_enabled);
> +               return kvm_handle_page_fault(vcpu, error_code, cr2, NULL, 0,
> +                               true);
>         }
>
>         ex_no = intr_info & INTR_INFO_VECTOR_MASK;