From: Paolo Bonzini <pbonzini@redhat.com>
Date: Wed, 8 Apr 2026 15:42:17 +0000 (-0400)
Subject: KVM: nSVM: enable GMET for guests
X-Git-Url: http://git.ipfire.org/gitweb/?a=commitdiff_plain;h=687ee95c1b6d7509a25bbc661e62801aa06cc2ae;p=thirdparty%2Flinux.git

KVM: nSVM: enable GMET for guests

All that needs to be done is moving the GMET bit from vmcb12 to vmcb02.
The only new thing is that __nested_copy_vmcb_control_to_cache now
ensures that ignored-if-unavailable bits are zero in svm->nested.ctl.

Tested-by: David Riley <d.riley@proxmox.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index 74a1df1cb84f..3d1fd1776e19 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -489,11 +489,14 @@ void __nested_copy_vmcb_control_to_cache(struct kvm_vcpu *vcpu,
 	nested_svm_sanitize_intercept(vcpu, to, SKINIT);
 	nested_svm_sanitize_intercept(vcpu, to, RDPRU);
 
-	/* Always clear SVM_MISC_ENABLE_NP if the guest cannot use NPTs */
+	/* Always clear misc_ctl bits that the guest cannot use */
 	to->misc_ctl = from->misc_ctl;
 	if (!guest_cpu_cap_has(vcpu, X86_FEATURE_NPT))
 		to->misc_ctl &= ~SVM_MISC_ENABLE_NP;
 
+	if (!gmet_enabled || !guest_cpu_cap_has(vcpu, X86_FEATURE_GMET))
+		to->misc_ctl &= ~SVM_MISC_ENABLE_GMET;
+
 	to->iopm_base_pa        = from->iopm_base_pa & PAGE_MASK;
 	to->msrpm_base_pa       = from->msrpm_base_pa & PAGE_MASK;
 	to->tsc_offset          = from->tsc_offset;
@@ -898,6 +901,7 @@ static void nested_vmcb02_prepare_control(struct vcpu_svm *svm)
 	/* Use vmcb01 MMU and format if guest does not use nNPT */
 	if (nested_npt_enabled(svm)) {
 		vmcb02->control.misc_ctl &= ~SVM_MISC_ENABLE_GMET;
+		vmcb02->control.misc_ctl |= (svm->nested.ctl.misc_ctl & SVM_MISC_ENABLE_GMET);
 
 		nested_svm_init_mmu_context(vcpu);
 	}
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index fd79874c5f4b..a82471a6d3ea 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -5504,6 +5504,9 @@ static __init void svm_set_cpu_caps(void)
 		if (boot_cpu_has(X86_FEATURE_PFTHRESHOLD))
 			kvm_cpu_cap_set(X86_FEATURE_PFTHRESHOLD);
 
+		if (gmet_enabled)
+			kvm_cpu_cap_set(X86_FEATURE_GMET);
+
 		if (vgif)
 			kvm_cpu_cap_set(X86_FEATURE_VGIF);