Re: [RFC] /dev/ioasid uAPI proposal

Jacob Pan
2021-06-03T18:16:58Z

Hi Shenming,

On Wed, 2 Jun 2021 12:50:26 +0800, Shenming Lu <lushenming@huawei.com>
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.

> Thanks,
> Shenming
>

Thanks,

Jacob