On 21.11.2023 17:24, Roger Pau Monné wrote:
> On Thu, Nov 16, 2023 at 02:31:05PM +0100, Jan Beulich wrote:
>> ... or we fail to enable the functionality on the BSP for other reasons.
>> The only place where hardware announcing the feature is recorded is the
>> raw CPU policy/featureset.
>>
>> Inspired by
>> https://lore.kernel.org/all/[email protected]/.
>>
>> Signed-off-by: Jan Beulich <[email protected]>
>
> Acked-by: Roger Pau Monné <[email protected]>
Thanks.
>> --- a/xen/arch/x86/hvm/vmx/vmcs.c
>> +++ b/xen/arch/x86/hvm/vmx/vmcs.c
>> @@ -2163,6 +2163,23 @@ int __init vmx_vmcs_init(void)
>>
>> if ( !ret )
>> register_keyhandler('v', vmcs_dump, "dump VT-x VMCSs", 1);
>> + else
>> + {
>> + setup_clear_cpu_cap(X86_FEATURE_VMX);
>> +
>> + /*
>> + * _vmx_vcpu_up() may have made it past feature identification.
>> + * Make sure all dependent features are off as well.
>> + */
>> + vmx_basic_msr = 0;
>> + vmx_pin_based_exec_control = 0;
>> + vmx_cpu_based_exec_control = 0;
>> + vmx_secondary_exec_control = 0;
>> + vmx_vmexit_control = 0;
>> + vmx_vmentry_control = 0;
>> + vmx_ept_vpid_cap = 0;
>> + vmx_vmfunc = 0;
>
> Are there really any usages of those variables if VMX is disabled in
> CPUID?
I wanted to be on the safe side, as to me the question was "Are there really
_no_ uses anywhere of those variables if VMX is disabled in CPUID?" And I
couldn't easily convince myself of this being the case, seeing how all of
vmcs.h's cpu_has_* are defined (and I'm pretty sure we have uses outside of
arch/x86/hvm/vmx/).
Jan
