Re: Direct rdtsc call side-effect

Thomas Gleixner
2023-06-01T10:31:31Z

On Thu, Jun 01 2023 at 10:56, Peter Zijlstra wrote:
> On Thu, Jun 01, 2023 at 01:45:35PM +0500, Muhammad Usama Anjum wrote:
>> We are thinking of saving and restoring the timestamp counter at suspend
>> and resume time respectively. In theory it can work on Intel because of
>> TSC_ADJUST register. But it'll never work on AMD until:
>> * AMD supports the same kind of adjust register. (AMD has said that the
>> adjust register cannot be implemented in their firmware. They'll have to
>> add it to their hardware.)
>> * by manual synchronization in kernel (I know you don't like this idea. But
>> there is something Windows is doing to save/restore and sync the TSC)
>
> Wine could set TIF_NOTSC, which will cause it to run with CR4.TSD
> cleared and cause RDTSC to #GP, at which point you can emulate it.

We should ask Microsoft to do the same. That'll fix the direct RDTSC
usage quickly. :)