On Wed, 30 Jul 2025 17:47:52 -0400
Peter Xu <[email protected]> wrote:
> On Wed, Jul 30, 2025 at 02:39:29PM +0200, Igor Mammedov wrote:
> > diff --git a/system/memory.c b/system/memory.c
> > index 5646547940..9a5a262112 100644
> > --- a/system/memory.c
> > +++ b/system/memory.c
> > @@ -2546,6 +2546,12 @@ void
> > memory_region_clear_flush_coalesced(MemoryRegion *mr)
> > }
> > }
> >
> > +void memory_region_enable_lockless_io(MemoryRegion *mr)
> > +{
> > + mr->lockless_io = true;
/*
* reentrancy_guard has per device scope, that when enabled
* will effectively prevent concurrent access to device's IO
* MemoryRegion(s) by not calling accessor callback.
*
* Turn it off for lock-less IO enabled devices, to allow
* concurrent IO.
* TODO: remove this when reentrancy_guard becomes per transaction.
*/
would something like this be sufficient?
> > + mr->disable_reentrancy_guard = true;
>
> IIUC this is needed only because the re-entrancy guard is not
> per-transaction but per-device, am I right?
>
> Maybe some comment would be nice here to explain how mmio concurrency could
> affect this. If my above comment is correct, it could also be a TODO so we
> could re-enable this when it is per-transaction (even though I don't know
> whether it's easy / useful to do..).
>
> Thanks,
>
