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

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Message-Id: <20210217145718.1217358-6-mlevitsk@redhat.com>
Date:   Wed, 17 Feb 2021 16:57:16 +0200
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     kvm@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, Wanpeng Li <wanpengli@...cent.com>,
        Borislav Petkov <bp@...en8.de>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Joerg Roedel <joro@...tes.org>,
        Jim Mattson <jmattson@...gle.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Sean Christopherson <seanjc@...gle.com>,
        x86@...nel.org (maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)),
        Thomas Gleixner <tglx@...utronix.de>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Ingo Molnar <mingo@...hat.com>,
        Maxim Levitsky <mlevitsk@...hat.com>
Subject: [PATCH 5/7] KVM: nSVM: fix running nested guests when npt=0

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@...hat.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;
 
+
 	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);
-- 
2.26.2