From 2abb25273c82061dd4670690c81c319c03740bf6 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Thu, 13 Aug 2026 14:44:03 -0700 Subject: [PATCH] KVM: nVMX: Force MSR bitmap refresh if runtime eVMCS controls are modified Force a refresh of the vmcs02 MSR bitmap during nested VM-Enter if the runtime eVMCS controls (pin, primary, secondary, etc.) are being updated. If L1 isn't intercepting TPR writes, runs L2 with TPR virtualization, and then runs the same L2 with TPR virtualization disabled, KVM will fail to refresh msr_bitmap02 and leave TPR in passthrough mode even though TPR virtualization is disabled. I.e. failure to refresh the bitmap lets L2 (or L1 by proxy) read and write L0's TPR. Fixes: 502d2bf5f2fd ("KVM: nVMX: Implement Enlightened MSR Bitmap feature") Cc: stable@vger.kernel.org Reviewed-by: Vitaly Kuznetsov Signed-off-by: Sean Christopherson Signed-off-by: Paolo Bonzini --- arch/x86/kvm/vmx/nested.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index 40c1a5f6fa8a..b25216862740 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -1754,6 +1754,9 @@ static void copy_vmcs12_to_shadow(struct vcpu_vmx *vmx) static void copy_enlightened_to_vmcs12(struct vcpu_vmx *vmx, u32 hv_clean_fields) { #ifdef CONFIG_KVM_HYPERV + const u64 runtime_controls = HV_VMX_ENLIGHTENED_CLEAN_FIELD_CONTROL_GRP1 | + HV_VMX_ENLIGHTENED_CLEAN_FIELD_CONTROL_GRP2 | + HV_VMX_ENLIGHTENED_CLEAN_FIELD_CONTROL_PROC; struct vmcs12 *vmcs12 = vmx->nested.cached_vmcs12; struct hv_enlightened_vmcs *evmcs = nested_vmx_evmcs(vmx); struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(&vmx->vcpu); @@ -1762,6 +1765,9 @@ static void copy_enlightened_to_vmcs12(struct vcpu_vmx *vmx, u32 hv_clean_fields vmcs12->tpr_threshold = evmcs->tpr_threshold; vmcs12->guest_rip = evmcs->guest_rip; + if ((hv_clean_fields & runtime_controls) != runtime_controls) + vmx->nested.force_msr_bitmap_recalc = true; + if (unlikely(!(hv_clean_fields & HV_VMX_ENLIGHTENED_CLEAN_FIELD_ENLIGHTENMENTSCONTROL))) { hv_vcpu->nested.pa_page_gpa = evmcs->partition_assist_page;