linux-kernel - [PATCH v2 2/2] KVM:SVM: Update cr3_lm_rsvd

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Message-ID: <160521948301.32054.5783800787423231162.stgit@bmoger-ubuntu>
Date:   Thu, 12 Nov 2020 16:18:03 -0600
From:   Babu Moger <babu.moger@....com>
To:     pbonzini@...hat.com
Cc:     junaids@...gle.com, wanpengli@...cent.com, kvm@...r.kernel.org,
        joro@...tes.org, x86@...nel.org, linux-kernel@...r.kernel.org,
        sean.j.christopherson@...el.com, mingo@...hat.com, bp@...en8.de,
        hpa@...or.com, tglx@...utronix.de, vkuznets@...hat.com,
        jmattson@...gle.com
Subject: [PATCH v2 2/2] KVM:SVM: Update cr3_lm_rsvd_bits for AMD SEV guests

For AMD SEV guests, update the cr3_lm_rsvd_bits to mask
the memory encryption bit in reserved bits.

Signed-off-by: Babu Moger <babu.moger@....com>
---
 arch/x86/kvm/svm/svm.c |   11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 2f32fd09e259..b418eeabcccc 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -3741,6 +3741,7 @@ static u64 svm_get_mt_mask(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio)
 static void svm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
+	struct kvm_cpuid_entry2 *best;
 
 	vcpu->arch.xsaves_enabled = guest_cpuid_has(vcpu, X86_FEATURE_XSAVE) &&
 				    boot_cpu_has(X86_FEATURE_XSAVE) &&
@@ -3753,6 +3754,16 @@ static void svm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
 	/* Check again if INVPCID interception if required */
 	svm_check_invpcid(svm);
 
+	/*
+	 * For sev guests, update the cr3_lm_rsvd_bits to mask the memory
+	 * encryption bit from reserved bits
+	 */
+	if (sev_guest(vcpu->kvm)) {
+		best = kvm_find_cpuid_entry(vcpu, 0x8000001F, 0);
+		if (best)
+			vcpu->arch.cr3_lm_rsvd_bits &= ~(1UL << (best->ebx & 0x3f));
+	}
+
 	if (!kvm_vcpu_apicv_active(vcpu))
 		return;