linux-kernel - [PATCH 2/6] KVM: nSVM: Check that VM_HSAVE

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Message-Id: <20210628104425.391276-3-vkuznets@redhat.com>
Date:   Mon, 28 Jun 2021 12:44:21 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Maxim Levitsky <mlevitsk@...hat.com>,
        Cathy Avery <cavery@...hat.com>,
        Emanuele Giuseppe Esposito <eesposit@...hat.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Michael Roth <mdroth@...ux.vnet.ibm.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 2/6] KVM: nSVM: Check that VM_HSAVE_PA MSR was set before VMRUN

APM states that "The address written to the VM_HSAVE_PA MSR, which holds
the address of the page used to save the host state on a VMRUN, must point
to a hypervisor-owned page. If this check fails, the WRMSR will fail with
a #GP(0) exception. Note that a value of 0 is not considered valid for the
VM_HSAVE_PA MSR and a VMRUN that is attempted while the HSAVE_PA is 0 will
fail with a #GP(0) exception."

svm_set_msr() already checks that the supplied address is valid, so only
check for '0' is missing. Add it to nested_svm_vmrun().

Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
---
 arch/x86/kvm/svm/nested.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index 21d03e3a5dfd..1c6b0698b52e 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -618,6 +618,11 @@ int nested_svm_vmrun(struct kvm_vcpu *vcpu)
 	struct kvm_host_map map;
 	u64 vmcb12_gpa;
 
+	if (!svm->nested.hsave_msr) {
+		kvm_inject_gp(vcpu, 0);
+		return 1;
+	}
+
 	if (is_smm(vcpu)) {
 		kvm_queue_exception(vcpu, UD_VECTOR);
 		return 1;
-- 
2.31.1