Re: [PATCH] x86/PoD: defer nested P2M flushes

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Tue, Oct 19, 2021 at 10:19:57AM +0200, Jan Beulich wrote:
> On 19.10.2021 10:17, Jan Beulich wrote:
> > On 19.10.2021 10:09, Roger Pau Monné wrote:
> >> On Mon, Oct 11, 2021 at 10:17:08AM +0200, Jan Beulich wrote:
> >>> @@ -1229,8 +1242,9 @@ p2m_pod_demand_populate(struct p2m_domai
> >>>          __trace_var(TRC_MEM_POD_POPULATE, 0, sizeof(t), &t);
> >>>      }
> >>>  
> >>> -    pod_unlock(p2m);
> >>> +    pod_unlock_and_flush(p2m);
> >>>      return true;
> >>> +
> >>>  out_of_memory:
> >>>      pod_unlock(p2m);
> >>
> >> Don't you need to set defer_nested_flush = false in the out_of_memory
> >> label? (as you don't call pod_unlock_and_flush that would do it)
> > 
> > Yes of course - thanks for spotting. I had pod_unlock_and_flush() here
> > too initially, and when switching back I forgot to convert rather than
> > just delete that.
> 
> Oh, wait, that was on purpose: There's no point clearing the flag
> when the next thing we do is invoke domain_crash(). If it wasn't
> that way, I don't think I could avoid using pod_unlock_and_flush()
> here as well.

Oh, I see. We would need to be careful if that domain crash is ever
removed.

Thanks, Roger.