linux-kernel - [PATCH v2 1/3] Revert "KVM: SVM: Allow EFER.LMSLE to be set with nested svm"

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Message-ID: <20220920205922.1564814-2-jmattson@google.com>
Date:   Tue, 20 Sep 2022 13:59:20 -0700
From:   Jim Mattson <jmattson@...gle.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H . Peter Anvin" <hpa@...or.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     Jim Mattson <jmattson@...gle.com>
Subject: [PATCH v2 1/3] Revert "KVM: SVM: Allow EFER.LMSLE to be set with
 nested svm"

Revert the hack that allowed a guest to set EFER.LMSLE, since no
attempt was ever made to properly virtualize the feature.

Now that AMD has deprecated the feature, the ROI for properly
virtualizing it is vanishingly small.

This reverts commit eec4b140c924b4c650e9a89e01d223266490e325.

Fixes: eec4b140c924 ("KVM: SVM: Allow EFER.LMSLE to be set with nested svm")
Signed-off-by: Jim Mattson <jmattson@...gle.com>
---
 arch/x86/include/asm/msr-index.h | 2 --
 arch/x86/kvm/svm/svm.c           | 2 +-
 2 files changed, 1 insertion(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index 6674bdb096f3..0a0426f284a3 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -28,7 +28,6 @@
 #define _EFER_LMA		10 /* Long mode active (read-only) */
 #define _EFER_NX		11 /* No execute enable */
 #define _EFER_SVME		12 /* Enable virtualization */
-#define _EFER_LMSLE		13 /* Long Mode Segment Limit Enable */
 #define _EFER_FFXSR		14 /* Enable Fast FXSAVE/FXRSTOR */
 
 #define EFER_SCE		(1<<_EFER_SCE)
@@ -36,7 +35,6 @@
 #define EFER_LMA		(1<<_EFER_LMA)
 #define EFER_NX			(1<<_EFER_NX)
 #define EFER_SVME		(1<<_EFER_SVME)
-#define EFER_LMSLE		(1<<_EFER_LMSLE)
 #define EFER_FFXSR		(1<<_EFER_FFXSR)
 
 /* Intel MSRs. Some also available on other CPUs */
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index f3813dbacb9f..3af360fe21e6 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -5012,7 +5012,7 @@ static __init int svm_hardware_setup(void)
 
 	if (nested) {
 		printk(KERN_INFO "kvm: Nested Virtualization enabled\n");
-		kvm_enable_efer_bits(EFER_SVME | EFER_LMSLE);
+		kvm_enable_efer_bits(EFER_SVME);
 	}
 
 	/*
-- 
2.37.3.968.ga6b4b080e4-goog