linux-kernel - [PATCH 2/2] KVM: SVM: fix emulation of msr reads/writes of MSR_FS_BASE and MSR_GS

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Message-Id: <20240725150110.327601-3-mlevitsk@redhat.com>
Date: Thu, 25 Jul 2024 11:01:10 -0400
From: Maxim Levitsky <mlevitsk@...hat.com>
To: kvm@...r.kernel.org
Cc: Dave Hansen <dave.hansen@...ux.intel.com>,
	Sean Christopherson <seanjc@...gle.com>,
	Borislav Petkov <bp@...en8.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	x86@...nel.org,
	linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...hat.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Maxim Levitsky <mlevitsk@...hat.com>
Subject: [PATCH 2/2] KVM: SVM: fix emulation of msr reads/writes of MSR_FS_BASE and MSR_GS_BASE

If these msrs are read by the emulator (e.g due to 'force emulation' prefix),
SVM code currently fails to extract the corresponding segment bases,
and return them to the emulator.

Fix that.

Signed-off-by: Maxim Levitsky <mlevitsk@...hat.com>
---
 arch/x86/kvm/svm/svm.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index c58da281f14f..3fc01ba2bd4a 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -2875,6 +2875,12 @@ static int svm_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 	case MSR_CSTAR:
 		msr_info->data = svm->vmcb01.ptr->save.cstar;
 		break;
+	case MSR_GS_BASE:
+		msr_info->data = svm->vmcb01.ptr->save.gs.base;
+		break;
+	case MSR_FS_BASE:
+		msr_info->data = svm->vmcb01.ptr->save.fs.base;
+		break;
 	case MSR_KERNEL_GS_BASE:
 		msr_info->data = svm->vmcb01.ptr->save.kernel_gs_base;
 		break;
@@ -3100,6 +3106,12 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
 	case MSR_CSTAR:
 		svm->vmcb01.ptr->save.cstar = data;
 		break;
+	case MSR_GS_BASE:
+		svm->vmcb01.ptr->save.gs.base = data;
+		break;
+	case MSR_FS_BASE:
+		svm->vmcb01.ptr->save.fs.base = data;
+		break;
 	case MSR_KERNEL_GS_BASE:
 		svm->vmcb01.ptr->save.kernel_gs_base = data;
 		break;
-- 
2.26.3