Re: [PATCH v15 09/13] tsc: Use the GUEST_TSC_FREQ MSR for discovering TSC frequency

Nikunj A. Dadhania
2024-12-17T07:57:43Z

On 12/17/2024 12:35 PM, Tom Lendacky wrote:
> On 12/17/24 00:27, Nikunj A Dadhania wrote:
>> On 12/16/2024 10:01 PM, Tom Lendacky wrote:
>>> On 12/3/24 03:00, Nikunj A Dadhania wrote:
>>>> Calibrating the TSC frequency using the kvmclock is not correct for
>>>> SecureTSC enabled guests. Use the platform provided TSC frequency via the
>>>> GUEST_TSC_FREQ MSR (C001_0134h).
>>>>
>>>> Signed-off-by: Nikunj A Dadhania <nikunj@amd.com>
>>>> ---
>>>> arch/x86/include/asm/sev.h | 2 ++
>>>> arch/x86/coco/sev/core.c | 16 ++++++++++++++++
>>>> arch/x86/kernel/tsc.c | 5 +++++
>>>> 3 files changed, 23 insertions(+)
>>>>
>
>> @@ -3282,16 +3283,18 @@ void __init snp_secure_tsc_prepare(void)
>>
>> static unsigned long securetsc_get_tsc_khz(void)
>> {
>> - unsigned long long tsc_freq_mhz;
>> -
>> setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ);
>
> I was thinking even this can be moved.

Yes, I am testing that out. If there is no dependency, I will move it.

Regards,
Nikunj