On Thu, Nov 16, 2023 at 02:32:47PM +0100, Jan Beulich wrote: > This was used by VMX only, and the intended VMCS write can as well > happen from vmx_set_tsc_offset(), invoked (directly or indirectly) > almost immediately after the present call sites of the hook. > vmx_set_tsc_offset() isn't invoked frequently elsewhere, so the extra > VMCS write shouldn't raise performance concerns. > > Signed-off-by: Jan Beulich <[email protected]>
Acked-by: Roger Pau Monné <[email protected]> I would be lying if I told you I understand guest TSC management in Xen, but patch does keep the previous call sites with adding others that are indeed not hot paths. I do wonder whether it would be possible to set this before the domain is started, as AFAICT the TSC scaling ratio is only set before the domain is started (either by domain create or other toolstack hypercalls). Could we maybe further limit the write to the case where the vCPU is not running? Thanks, Roger.
