Re: [RFC] /dev/ioasid uAPI proposal

[Jason Wang]

在 2021/6/4 上午2:19, Jacob Pan 写道:
> Hi Shenming,
>
> On Wed, 2 Jun 2021 12:50:26 +0800, Shenming Lu <lushenming@xxxxxxxxxx>
> wrote:
>
> > On 2021/6/2 1:33, Jason Gunthorpe wrote:
> > > On Tue, Jun 01, 2021 at 08:30:35PM +0800, Lu Baolu wrote:
> > >    
> > > > The drivers register per page table fault handlers to /dev/ioasid which
> > > > will then register itself to iommu core to listen and route the per-
> > > > device I/O page faults.
> > > I'm still confused why drivers need fault handlers at all?
> > Essentially it is the userspace that needs the fault handlers,
> > one case is to deliver the faults to the vIOMMU, and another
> > case is to enable IOPF on the GPA address space for on-demand
> > paging, it seems that both could be specified in/through the
> > IOASID_ALLOC ioctl?
> I would think IOASID_BIND_PGTABLE is where fault handler should be
> registered. There wouldn't be any IO page fault without the binding anyway.
>
> I also don't understand why device drivers should register the fault
> handler, the fault is detected by the pIOMMU and injected to the vIOMMU. So
> I think it should be the IOASID itself register the handler.


As discussed in another thread.

I think the reason is that ATS doesn't forbid the #PF to be reported via 
a device specific way.

Thanks


> > Thanks,
> > Shenming
>
> Thanks,
>
> Jacob