linux-kernel - [PATCH 2/2] KVM:SVM: Mask SEV encryption bit from CR3 reserved bits

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Date:   Wed, 11 Nov 2020 18:28:26 -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 2/2] KVM:SVM: Mask SEV encryption bit from CR3 reserved bits

Add support to the mask_cr3_rsvd_bits() callback to mask the
encryption bit from the CR3 value when SEV is enabled.

Additionally, cache the encryption mask for quick access during
the check.

Fixes: a780a3ea628268b2 ("KVM: X86: Fix reserved bits check for MOV to CR3")
Signed-off-by: Babu Moger <babu.moger@....com>
---
 arch/x86/kvm/svm/svm.c |   11 ++++++++++-
 arch/x86/kvm/svm/svm.h |    3 +++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index a491a47d7f5c..c2b1e52810c6 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) &&
@@ -3771,6 +3772,12 @@ static void svm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
 	if (nested && guest_cpuid_has(vcpu, X86_FEATURE_SVM))
 		kvm_request_apicv_update(vcpu->kvm, false,
 					 APICV_INHIBIT_REASON_NESTED);
+
+	best = kvm_find_cpuid_entry(vcpu, 0x8000001F, 0);
+	if (best)
+		svm->sev_enc_mask = ~(1UL << (best->ebx & 0x3f));
+	else
+		svm->sev_enc_mask = ~0UL;
 }
 
 static bool svm_has_wbinvd_exit(void)
@@ -4072,7 +4079,9 @@ static void enable_smi_window(struct kvm_vcpu *vcpu)
 
 static unsigned long svm_mask_cr3_rsvd_bits(struct kvm_vcpu *vcpu, unsigned long cr3)
 {
-	return cr3;
+	struct vcpu_svm *svm = to_svm(vcpu);
+
+	return sev_guest(vcpu->kvm) ? (cr3 & svm->sev_enc_mask) : cr3;
 }
 
 static bool svm_can_emulate_instruction(struct kvm_vcpu *vcpu, void *insn, int insn_len)
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 1d853fe4c778..57a36645a0e4 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -152,6 +152,9 @@ struct vcpu_svm {
 	u64 *avic_physical_id_cache;
 	bool avic_is_running;
 
+	/* SEV Memory encryption mask */
+	unsigned long sev_enc_mask;
+
 	/*
 	 * Per-vcpu list of struct amd_svm_iommu_ir:
 	 * This is used mainly to store interrupt remapping information used