Similar to exit_ctls_low, entry_ctls_low, procbased_ctls_low, pinbased_ctls_low should be set to PIN_BASED_ALWAYSON_WITHOUT_TRUE_MSR and not host's MSR_IA32_VMX_PINBASED_CTLS value |= PIN_BASED_ALWAYSON_WITHOUT_TRUE_MSR. The commit eabeaaccfca0 ("KVM: nVMX: Clean up and fix pin-based execution controls") which introduced '|=' doesn't mention anything about why this is needed, the change seems rather accidental. Note: normally, required-1 portion of MSR_IA32_VMX_PINBASED_CTLS should be equal to PIN_BASED_ALWAYSON_WITHOUT_TRUE_MSR so no behavioral change is expected, however, it is (in theory) possible to observe something different there when e.g. KVM is running as a nested hypervisor. Hope this doesn't happen in practice. Reported-by: Jim Mattson <jmattson@xxxxxxxxxx> Reviewed-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx> Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> --- arch/x86/kvm/vmx/nested.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index dcf3ee645212..09654d5c2144 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -6586,7 +6586,7 @@ void nested_vmx_setup_ctls_msrs(struct nested_vmx_msrs *msrs, u32 ept_caps) rdmsr(MSR_IA32_VMX_PINBASED_CTLS, msrs->pinbased_ctls_low, msrs->pinbased_ctls_high); - msrs->pinbased_ctls_low |= + msrs->pinbased_ctls_low = PIN_BASED_ALWAYSON_WITHOUT_TRUE_MSR; msrs->pinbased_ctls_high &= PIN_BASED_EXT_INTR_MASK | -- 2.35.3