On 25.08.2022 12:13, Juergen Gross wrote: > On 25.08.22 11:50, Jan Beulich wrote: >> On 25.08.2022 11:26, Juergen Gross wrote: >>> --- a/drivers/xen/privcmd.c >>> +++ b/drivers/xen/privcmd.c >>> @@ -602,6 +602,10 @@ static int lock_pages( >>> *pinned += page_count; >>> nr_pages -= page_count; >>> pages += page_count; >>> + >>> + /* Exact reason isn't known, EFAULT is one possibility. */ >>> + if (page_count < requested) >>> + return -EFAULT; >>> } >> >> I don't really know the inner workings of pin_user_pages_fast() >> nor what future plans there are with it. To be as independent of >> its behavior as possible, how about bailing here only when >> page_count actually is zero (i.e. no forward progress)? > > This would require to rework the loop in lock_pages() to be able to > handle only a partial buffer. Oh, I see - I've misread the code as if the loop was capping each iteration's count to the capacity of some internal buffer (as iirc is being done elsewhere). So ... > This would add some complexity, but OTOH I'd get an exact error code > back in case of failure. ... perhaps not worth it then, ... > I'll have a try and see how the result would look like. ... unless you think this might be relevant in certain cases. Jan
