On 10/24/2024 4:44 PM, Nikunj A. Dadhania wrote:
On 10/24/2024 1:26 PM, Xiaoyao Li wrote:
On 10/21/2024 1:51 PM, Nikunj A Dadhania wrote:
The hypervisor should not be intercepting RDTSC/RDTSCP when Secure TSC is
enabled. A #VC exception will be generated if the RDTSC/RDTSCP instructions
are being intercepted. If this should occur and Secure TSC is enabled,
terminate guest execution.
There is another option to ignore the interception and just return back to
guest execution.
That is not correct, RDTSC/RDTSCP should return the timestamp counter value
computed using the GUEST_TSC_SCALE and GUEST_TSC_OFFSET part of VMSA.
Ah, I missed this. Yes, if ignore the interception, guest needs to do
TSC scale itself with GUEST_TSC_SCALE and GUEST_TSC_OFFSET to get the
correct TSC. It's complicating things while making not intercepting
RDTSC/RDTSP a hard requirement is much simple.
I think it's worth adding it as the justification.
I think it better to add some justification on why make it> fatal and terminate the guest is better than ignoring the interception.
How about the below updated commit message:
The hypervisor should not be intercepting RDTSC/RDTSCP when Secure TSC is
enabled. A #VC exception will be generated if the RDTSC/RDTSCP instructions
are being intercepted. If this should occur and Secure TSC is enabled,
terminate guest execution as the guest cannot rely on the TSC value provided
by the hypervisor.
Regards
Nikunj
