linux-kernel - [PATCH 2/2] nSVM: delay MSR permission processing to first nested VM run

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Message-Id: <20200928115144.2446240-3-pbonzini@redhat.com>
Date:   Mon, 28 Sep 2020 07:51:44 -0400
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     mlevitsk@...hat.com
Subject: [PATCH 2/2] nSVM: delay MSR permission processing to first nested VM run

Allow userspace to set up the memory map after KVM_SET_NESTED_STATE;
to do so, move the call to nested_svm_vmrun_msrpm inside the
KVM_REQ_GET_NESTED_STATE_PAGES handler (which is currently
not used by nSVM).  This is similar to what VMX does already.

Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 arch/x86/kvm/svm/nested.c | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index 598a769f1961..ab7ff2701dec 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -200,6 +200,20 @@ static bool nested_svm_vmrun_msrpm(struct vcpu_svm *svm)
 	return true;
 }
 
+static bool svm_get_nested_state_pages(struct kvm_vcpu *vcpu)
+{
+	struct vcpu_svm *svm = to_svm(vcpu);
+	if (!nested_svm_vmrun_msrpm(svm)) {
+		vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
+		vcpu->run->internal.suberror =
+			KVM_INTERNAL_ERROR_EMULATION;
+		vcpu->run->internal.ndata = 0;
+		return false;
+	}
+
+	return true;
+}
+
 static bool nested_vmcb_check_controls(struct vmcb_control_area *control)
 {
 	if ((control->intercept & (1ULL << INTERCEPT_VMRUN)) == 0)
@@ -702,6 +716,8 @@ void svm_leave_nested(struct vcpu_svm *svm)
 		copy_vmcb_control_area(&vmcb->control, &hsave->control);
 		nested_svm_uninit_mmu_context(&svm->vcpu);
 	}
+
+	kvm_clear_request(KVM_REQ_GET_NESTED_STATE_PAGES, &svm->vcpu);
 }
 
 static int nested_svm_exit_handled_msr(struct vcpu_svm *svm)
@@ -1147,8 +1163,7 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu,
 	load_nested_vmcb_control(svm, ctl);
 	nested_prepare_vmcb_control(svm);
 
-	if (!nested_svm_vmrun_msrpm(svm))
-		return -EINVAL;
+	kvm_make_request(KVM_REQ_GET_NESTED_STATE_PAGES, vcpu);
 
 out_set_gif:
 	svm_set_gif(svm, !!(kvm_state->flags & KVM_STATE_NESTED_GIF_SET));
@@ -1163,6 +1178,7 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu,
 
 struct kvm_x86_nested_ops svm_nested_ops = {
 	.check_events = svm_check_nested_events,
+	.get_nested_state_pages = svm_get_nested_state_pages,
 	.get_state = svm_get_nested_state,
 	.set_state = svm_set_nested_state,
 };
-- 
2.26.2