On 10/31/2023 2:30 AM, Tom Lendacky wrote:
> On 10/30/23 01:36, Nikunj A Dadhania wrote:
>> For AMD SNP guests having Secure TSC enabled, skip using the kvmclock.
>> The guest kernel will fallback and use Secure TSC based clocksource.
>>
>> Signed-off-by: Nikunj A Dadhania <nikunj@xxxxxxx>
>> ---
>> arch/x86/kernel/kvmclock.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
>> index fb8f52149be9..779e7311fa6f 100644
>> --- a/arch/x86/kernel/kvmclock.c
>> +++ b/arch/x86/kernel/kvmclock.c
>> @@ -288,7 +288,7 @@ void __init kvmclock_init(void)
>> {
>> u8 flags;
>> - if (!kvm_para_available() || !kvmclock)
>> + if (!kvm_para_available() || !kvmclock || cc_platform_has(CC_ATTR_GUEST_SECURE_TSC))
>
> And is setting X86_FEATURE_TSC_RELIABLE, as Dave Hansen suggests, enough
> to prevent usage of kvmclock?
No that wasn't sufficient. kvmclock was always selected before SecureTSC even when X86_FEATURE_TSC_RELIABLE was selected.
>
> There was a discussion here:
> https://lore.kernel.org/lkml/20230808162320.27297-1-kirill.shutemov@xxxxxxxxxxxxxxx/
>
> Thanks,
> Tom
Regards
Nikunj
