linux-kernel - [PATCH v2 32/46] KVM: SVM: Stuff save->dr6 at during VMSA sync, not at RESET/INIT

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Message-Id: <20210713163324.627647-33-seanjc@google.com>
Date:   Tue, 13 Jul 2021 09:33:10 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Reiji Watanabe <reijiw@...gle.com>
Subject: [PATCH v2 32/46] KVM: SVM: Stuff save->dr6 at during VMSA sync, not
 at RESET/INIT

Move code to stuff vmcb->save.dr6 to its architectural init value from
svm_vcpu_reset() into sev_es_sync_vmsa().  Except for protected guests,
a.k.a. SEV-ES guests, vmcb->save.dr6 is set during VM-Enter, i.e. the
extra write is unnecessary.  For SEV-ES, stuffing save->dr6 handles a
theoretical case where the VMSA could be encrypted before the first
KVM_RUN.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/svm/sev.c | 1 +
 arch/x86/kvm/svm/svm.c | 1 -
 2 files changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 8d36f0c73071..e34ee60fc9d7 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -583,6 +583,7 @@ static int sev_es_sync_vmsa(struct vcpu_svm *svm)
 	save->xcr0 = svm->vcpu.arch.xcr0;
 	save->pkru = svm->vcpu.arch.pkru;
 	save->xss  = svm->vcpu.arch.ia32_xss;
+	save->dr6  = svm->vcpu.arch.dr6;
 
 	/*
 	 * SEV-ES will use a VMSA that is pointed to by the VMCB, not
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 6eff7f1a4672..251b230b2fef 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -1265,7 +1265,6 @@ static void init_vmcb(struct kvm_vcpu *vcpu)
 	svm_set_cr0(vcpu, X86_CR0_NW | X86_CR0_CD | X86_CR0_ET);
 	svm_set_cr4(vcpu, 0);
 	svm_set_efer(vcpu, 0);
-	save->dr6 = 0xffff0ff0;
 	kvm_set_rflags(vcpu, X86_EFLAGS_FIXED);
 	vcpu->arch.regs[VCPU_REGS_RIP] = 0x0000fff0;
 
-- 
2.32.0.93.g670b81a890-goog