Re: [PATCH 5/7] KVM: nSVM: fix running nested guests when npt=0

From: Maxim Levitsky <mlevitsk@redhat.com>
To: kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, Wanpeng Li <wanpengli@tencent.com>,
	Borislav Petkov <bp@alien8.de>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Joerg Roedel <joro@8bytes.org>, Jim Mattson <jmattson@google.com>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Sean Christopherson <seanjc@google.com>,
	"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
	<x86@kernel.org>, Thomas Gleixner <tglx@linutronix.de>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Ingo Molnar <mingo@redhat.com>
Subject: Re: [PATCH 5/7] KVM: nSVM: fix running nested guests when npt=0
Date: Wed, 17 Feb 2021 17:27:11 +0200	[thread overview]
Message-ID: <a458e946b469329b03a3f58ffa7ebd48c27005bb.camel@redhat.com> (raw)
In-Reply-To: <20210217145718.1217358-6-mlevitsk@redhat.com>

On Wed, 2021-02-17 at 16:57 +0200, Maxim Levitsky wrote:
> In case of npt=0 on host,
> nSVM needs the same .inject_page_fault tweak as VMX has,
> to make sure that shadow mmu faults are injected as vmexits.
> 
> Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
> ---
>  arch/x86/kvm/svm/nested.c | 18 ++++++++++++++++++
>  arch/x86/kvm/svm/svm.c    |  5 ++++-
>  arch/x86/kvm/svm/svm.h    |  1 +
>  3 files changed, 23 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
> index 1bc31e2e8fe0..53b9037259b5 100644
> --- a/arch/x86/kvm/svm/nested.c
> +++ b/arch/x86/kvm/svm/nested.c
> @@ -53,6 +53,23 @@ static void nested_svm_inject_npf_exit(struct kvm_vcpu *vcpu,
>  	nested_svm_vmexit(svm);
>  }
>  
> +void svm_inject_page_fault_nested(struct kvm_vcpu *vcpu, struct x86_exception *fault)
> +{
> +       struct vcpu_svm *svm = to_svm(vcpu);
> +       WARN_ON(!is_guest_mode(vcpu));
> +
> +       if (vmcb_is_intercept(&svm->nested.ctl, INTERCEPT_EXCEPTION_OFFSET + PF_VECTOR) &&
> +	   !svm->nested.nested_run_pending) {
> +               svm->vmcb->control.exit_code = SVM_EXIT_EXCP_BASE + PF_VECTOR;
> +               svm->vmcb->control.exit_code_hi = 0;
> +               svm->vmcb->control.exit_info_1 = fault->error_code;
> +               svm->vmcb->control.exit_info_2 = fault->address;
> +               nested_svm_vmexit(svm);
> +       } else {
> +               kvm_inject_page_fault(vcpu, fault);
> +       }
> +}
> +
>  static u64 nested_svm_get_tdp_pdptr(struct kvm_vcpu *vcpu, int index)
>  {
>  	struct vcpu_svm *svm = to_svm(vcpu);
> @@ -531,6 +548,7 @@ int enter_svm_guest_mode(struct vcpu_svm *svm, u64 vmcb12_gpa,
>  	if (ret)
>  		return ret;
>  
> +
Sorry for this whitespace change.
Best regards,
	Maxim Levitsky
>  	svm_set_gif(svm, true);
>  
>  	return 0;
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index 74a334c9902a..59e1767df030 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -3915,7 +3915,10 @@ static void svm_load_mmu_pgd(struct kvm_vcpu *vcpu, unsigned long root,
>  
>  static void svm_complete_mmu_init(struct kvm_vcpu *vcpu)
>  {
> -
> +	if (!npt_enabled && is_guest_mode(vcpu)) {
> +		WARN_ON(mmu_is_nested(vcpu));
> +		vcpu->arch.mmu->inject_page_fault = svm_inject_page_fault_nested;
> +	}
>  }
>  
>  static int is_disabled(void)
> diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
> index 7b6ca0e49a14..fda80d56c6e3 100644
> --- a/arch/x86/kvm/svm/svm.h
> +++ b/arch/x86/kvm/svm/svm.h
> @@ -437,6 +437,7 @@ static inline bool nested_exit_on_nmi(struct vcpu_svm *svm)
>  	return vmcb_is_intercept(&svm->nested.ctl, INTERCEPT_NMI);
>  }
>  
> +void svm_inject_page_fault_nested(struct kvm_vcpu *vcpu, struct x86_exception *fault);
>  int enter_svm_guest_mode(struct vcpu_svm *svm, u64 vmcb_gpa, struct vmcb *vmcb12);
>  void svm_leave_nested(struct vcpu_svm *svm);
>  void svm_free_nested(struct vcpu_svm *svm);