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SubjectRE: [PATCH RFC 10/11] iommu: Make IOPF handling framework generic
> From: Jean-Philippe Brucker <>
> Sent: Monday, March 21, 2022 7:42 PM
> Hi Kevin,
> On Mon, Mar 21, 2022 at 08:09:36AM +0000, Tian, Kevin wrote:
> > > From: Lu Baolu <>
> > > Sent: Sunday, March 20, 2022 2:40 PM
> > >
> > > The existing IOPF handling framework only handles the I/O page faults for
> > > SVA. Ginven that we are able to link iommu domain with each I/O page
> fault,
> > > we can now make the I/O page fault handling framework more general
> for
> > > more types of page faults.
> >
> > "make ... generic" in subject line is kind of confusing. Reading this patch I
> > think you really meant changing from per-device fault handling to per-
> domain
> > fault handling. This is more accurate in concept since the fault is caused by
> > the domain page table. 😊
> I tend to disagree with that last part. The fault is caused by a specific
> device accessing shared page tables. We should keep that device
> information throughout the fault handling, so that we can report it to the
> driver when things go wrong. A process can have multiple threads bound to
> different devices, they share the same mm so if the driver wanted to
> signal a misbehaving thread, similarly to a SEGV on the CPU side, it would
> need the device information to precisely report it to userspace.

iommu driver can include the device information in the fault data. But
in concept the IOPF should be reported per domain.

and I agree with Jason that at most we can send SEGV to the entire thread
group since there is no way to associate a DMA back to a thread which
initiates the DMA.


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