On Tue, Feb 18, 2025 at 02:50:46PM -0400, Jason Gunthorpe wrote:
> On Tue, Feb 18, 2025 at 10:28:04AM -0800, Nicolin Chen wrote:
> > On Tue, Feb 18, 2025 at 01:18:21PM -0400, Jason Gunthorpe wrote:
> > > On Fri, Jan 24, 2025 at 04:30:42PM -0800, Nicolin Chen wrote:
> > >
> > > > @@ -1831,31 +1831,30 @@ static int arm_smmu_handle_event(struct arm_smmu_device *smmu,
> > > > return -EOPNOTSUPP;
> > > > }
> > >
> > > There is still the filter at the top:
> > >
> > > switch (event->id) {
> > > case EVT_ID_TRANSLATION_FAULT:
> > > case EVT_ID_ADDR_SIZE_FAULT:
> > > case EVT_ID_ACCESS_FAULT:
> > > case EVT_ID_PERMISSION_FAULT:
> > > break;
> > > default:
> > > return -EOPNOTSUPP;
> > > }
> > >
> > > Is that right here or should more event types be forwarded to the
> > > guest?
> >
> > That doesn't seem to be right. Something like EVT_ID_BAD_CD_CONFIG
> > should be forwarded too. I will go through the list.
>
> I think the above should decode into a 'faultable' path because they
> all decode to something with an IOVA
>
> The rest should decode to things that include a SID and the SID decode
> should always be forwarded to the VM. Maybe there are small
> exclusions, but generally that is how I would see it..
Ack. SMMU spec defines three type:
"Three categories of events might be recorded into the Event queue:
• Configuration errors.
• Faults from the translation process.
• Miscellaneous."
The driver cares the first two only, as you remarked here.
> > > This already holds the streams_mutex across all of this, do you think
> > > we should get rid of the vmaster_rwsem and hold the streams_mutex on
> > > write instead?
> >
> > They are per master v.s. per smmu. The latter one would make master
> > commits/attaches exclusive, which feels unnecessary to me, although
> > it would make the code here slightly cleaner..
>
> I'd pay the cost on the attach side to have a single lock on the fault
> side..
OK. Maybe a small patch to turn the streams_mutex to streams_rwsem?
Thanks
Nicolin
