On Mon, Apr 12, 2021 at 07:55:01AM -0500, Brijesh Singh wrote:
> The cur_entry is updated by the hypervisor. While building the psc
> buffer the guest sets the cur_entry=0 and the end_entry point to the
> last valid entry. The cur_entry is incremented by the hypervisor after
> it successfully processes one 4K page. As per the spec, the hypervisor
> could get interrupted in middle of the page state change and cur_entry
> allows the guest to resume the page state change from the point where it
> was interrupted.
This is non-obvious and belongs in a comment above it. Otherwise it
looks weird.
> Since we can get interrupted while executing the PSC so just to be safe
> I re-initialized the scratch scratch area with our buffer instead of
> relying on old values.
Ditto.
> As per the spec the caller must check that the cur_entry > end_entry to
> determine whether all the entries are processed. If not then retry the
> state change. The hypervisor will skip the previously processed entries.
> The snp_page_state_vmgexit() is implemented to return only after all the
> entries are changed.
Ditto.
This whole mechanism of what the guest does and what the HV does, needs
to be explained in a bigger comment somewhere around there so that it is
clear what's going on.
Thx.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
