From 55a71224bd90aa485c72cc55c446a26b485a8e36 Mon Sep 17 00:00:00 2001 From: Jon Kohler Date: Wed, 8 Apr 2026 11:42:10 -0400 Subject: [PATCH] KVM: nVMX: allow MBEC with EVMCS Extend EVMCS1_SUPPORTED_2NDEXEC to allow MBEC and EVMCS to coexist. Presenting both EVMCS and MBEC simultaneously causes KVM to filter out MBEC and not present it as a supported control to the guest, preventing performance gains from MBEC when Windows HVCI is enabled. The guest may choose not to use MBEC (e.g., if the admin does not enable Windows HVCI / Memory Integrity), but if they use traditional nested virt (Hyper-V, WSL2, etc.), having EVMCS exposed is important for improving nested guest performance. IOW allowing MBEC and EVMCS to coexist provides maximum optionality to Windows users without overcomplicating VM administration. Signed-off-by: Jon Kohler Message-ID: <20251223054806.1611168-8-jon@nutanix.com> Tested-by: David Riley Signed-off-by: Paolo Bonzini --- arch/x86/kvm/vmx/hyperv_evmcs.h | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/x86/kvm/vmx/hyperv_evmcs.h b/arch/x86/kvm/vmx/hyperv_evmcs.h index fc7c4e7bd1bf..bc08fe40590e 100644 --- a/arch/x86/kvm/vmx/hyperv_evmcs.h +++ b/arch/x86/kvm/vmx/hyperv_evmcs.h @@ -87,6 +87,7 @@ SECONDARY_EXEC_PT_CONCEAL_VMX | \ SECONDARY_EXEC_BUS_LOCK_DETECTION | \ SECONDARY_EXEC_NOTIFY_VM_EXITING | \ + SECONDARY_EXEC_MODE_BASED_EPT_EXEC | \ SECONDARY_EXEC_ENCLS_EXITING) #define EVMCS1_SUPPORTED_3RDEXEC (0ULL)