linux-kernel - [RFC PATCH 28/35] KVM: X86: Update kvm_skip_emulated

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Date:   Mon, 14 Sep 2020 15:15:42 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org, x86@...nel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Brijesh Singh <brijesh.singh@....com>
Subject: [RFC PATCH 28/35] KVM: X86: Update kvm_skip_emulated_instruction() for an SEV-ES guest

From: Tom Lendacky <thomas.lendacky@....com>

The register state for an SEV-ES guest is encrypted so the value of the
RIP cannot be updated. For an automatic exit, the RIP will be advanced
as necessary. For a non-automatic exit, it is up to the #VC handler in
the guest to advance the RIP.

Add support to skip any RIP updates in kvm_skip_emulated_instruction()
for an SEV-ES guest.

Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
---
 arch/x86/kvm/x86.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 23564d02d158..1dbdca607511 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6874,13 +6874,17 @@ static int kvm_vcpu_do_singlestep(struct kvm_vcpu *vcpu)
 
 int kvm_skip_emulated_instruction(struct kvm_vcpu *vcpu)
 {
-	unsigned long rflags = kvm_x86_ops.get_rflags(vcpu);
+	unsigned long rflags;
 	int r;
 
 	r = kvm_x86_ops.skip_emulated_instruction(vcpu);
 	if (unlikely(!r))
 		return 0;
 
+	if (vcpu->arch.vmsa_encrypted)
+		return 1;
+
+	rflags = kvm_x86_ops.get_rflags(vcpu);
 	/*
 	 * rflags is the old, "raw" value of the flags.  The new value has
 	 * not been saved yet.
-- 
2.28.0