Re: [RFC] /dev/ioasid uAPI proposal

[Jacob Pan]

Hi Jason,

On Fri, 4 Jun 2021 09:30:37 +0800, Jason Wang <jasowang@xxxxxxxxxx> wrote:

> 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.
> 
Yes, in that case we should support both. Give the device driver a chance
to handle the IOPF if it can.

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


Thanks,

Jacob