On 2021/6/4 2:19, Jacob Pan wrote: > 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. Yeah, I also proposed this before, registering the handler in the BIND_PGTABLE ioctl does make sense for the guest page faults. :-) But how about the page faults from the GPA address space (it's page table is mapped through the MAP_DMA ioctl)? From your point of view, it seems that we should register the handler for the GPA address space in the (first) MAP_DMA ioctl. > > 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. Yeah, and it can also be said that the provider of the page table registers the handler (Baolu). Thanks, Shenming
