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From: Wei Huang <wei.huang2@amd.com>
To: kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, pbonzini@redhat.com,
	vkuznets@redhat.com, mlevitsk@redhat.com, seanjc@google.com,
	joro@8bytes.org, bp@alien8.de, tglx@linutronix.de,
	mingo@redhat.com, x86@kernel.org, jmattson@google.com,
	wanpengli@tencent.com, bsd@redhat.com, dgilbert@redhat.com,
	luto@amacapital.net, wei.huang2@amd.com
Subject: [PATCH v2 4/4] KVM: SVM: Support #GP handling for the case of nested on nested
Date: Thu, 21 Jan 2021 01:55:08 -0500	[thread overview]
Message-ID: <20210121065508.1169585-5-wei.huang2@amd.com> (raw)
In-Reply-To: <20210121065508.1169585-1-wei.huang2@amd.com>

Under the case of nested on nested (e.g. L0->L1->L2->L3), #GP triggered
by SVM instructions can be hided from L1. Instead the hypervisor can
inject the proper #VMEXIT to inform L1 of what is happening. Thus L1
can avoid invoking the #GP workaround. For this reason we turns on
guest VM's X86_FEATURE_SVME_ADDR_CHK bit for KVM running inside VM to
receive the notification and change behavior.

Co-developed-by: Bandan Das <bsd@redhat.com>
Signed-off-by: Bandan Das <bsd@redhat.com>
Signed-off-by: Wei Huang <wei.huang2@amd.com>
---
 arch/x86/kvm/svm/svm.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 2a12870ac71a..89512c0e7663 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -2196,6 +2196,11 @@ static int svm_instr_opcode(struct kvm_vcpu *vcpu)
 
 static int emulate_svm_instr(struct kvm_vcpu *vcpu, int opcode)
 {
+	const int guest_mode_exit_codes[] = {
+		[SVM_INSTR_VMRUN] = SVM_EXIT_VMRUN,
+		[SVM_INSTR_VMLOAD] = SVM_EXIT_VMLOAD,
+		[SVM_INSTR_VMSAVE] = SVM_EXIT_VMSAVE,
+	};
 	int (*const svm_instr_handlers[])(struct vcpu_svm *svm) = {
 		[SVM_INSTR_VMRUN] = vmrun_interception,
 		[SVM_INSTR_VMLOAD] = vmload_interception,
@@ -2203,7 +2208,14 @@ static int emulate_svm_instr(struct kvm_vcpu *vcpu, int opcode)
 	};
 	struct vcpu_svm *svm = to_svm(vcpu);
 
-	return svm_instr_handlers[opcode](svm);
+	if (is_guest_mode(vcpu)) {
+		svm->vmcb->control.exit_code = guest_mode_exit_codes[opcode];
+		svm->vmcb->control.exit_info_1 = 0;
+		svm->vmcb->control.exit_info_2 = 0;
+
+		return nested_svm_vmexit(svm);
+	} else
+		return svm_instr_handlers[opcode](svm);
 }
 
 /*
@@ -4034,6 +4046,11 @@ static void svm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
 	/* Check again if INVPCID interception if required */
 	svm_check_invpcid(svm);
 
+	if (nested && guest_cpuid_has(vcpu, X86_FEATURE_SVM)) {
+		best = kvm_find_cpuid_entry(vcpu, 0x8000000A, 0);
+		best->edx |= (1 << 28);
+	}
+
 	/* For sev guests, the memory encryption bit is not reserved in CR3.  */
 	if (sev_guest(vcpu->kvm)) {
 		best = kvm_find_cpuid_entry(vcpu, 0x8000001F, 0);
-- 
2.27.0


  parent reply	other threads:[~2021-01-21  7:48 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-21  6:55 [PATCH v2 0/4] Handle #GP for SVM execution instructions Wei Huang
2021-01-21  6:55 ` [PATCH v2 1/4] KVM: x86: Factor out x86 instruction emulation with decoding Wei Huang
2021-01-21 14:04   ` Maxim Levitsky
2021-01-21 14:23     ` Paolo Bonzini
2021-01-21 15:31       ` Wei Huang
2021-01-21  6:55 ` [PATCH v2 2/4] KVM: SVM: Add emulation support for #GP triggered by SVM instructions Wei Huang
2021-01-21 14:07   ` Maxim Levitsky
2021-01-21 16:06     ` Wei Huang
2021-01-21 16:55       ` Maxim Levitsky
2021-01-21 22:40         ` Sean Christopherson
2021-01-25 13:22           ` Maxim Levitsky
2021-01-21  6:55 ` [PATCH v2 3/4] KVM: SVM: Add support for VMCB address check change Wei Huang
2021-01-21 14:08   ` Maxim Levitsky
2021-01-21  6:55 ` Wei Huang [this message]
2021-01-21 14:09   ` [PATCH v2 4/4] KVM: SVM: Support #GP handling for the case of nested on nested Maxim Levitsky
2021-01-21 14:25   ` Paolo Bonzini
2021-01-21 14:56   ` Dr. David Alan Gilbert
2021-01-21 15:10     ` Maxim Levitsky

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