Re: [PATCH v7 7/9] iommu/vt-d: Allow qi_submit_sync() to return the QI faults

[Ethan Zhao]

On 12/27/2023 5:06 PM, Duan, Zhenzhong wrote:
> > -----Original Message-----
> > From: Liu, Yi L <yi.l.liu@xxxxxxxxx>
> > Sent: Tuesday, December 26, 2023 4:44 PM
> > Subject: Re: [PATCH v7 7/9] iommu/vt-d: Allow qi_submit_sync() to return
> > the QI faults
> >
> > On 2023/12/26 14:15, Yi Liu wrote:
> > > On 2023/12/26 12:13, Tian, Kevin wrote:
> > > > > From: Liu, Yi L <yi.l.liu@xxxxxxxxx>
> > > > > Sent: Tuesday, December 26, 2023 12:03 PM
> > > > >
> > > > > On 2023/12/22 12:23, Tian, Kevin wrote:
> > > > > > > From: Liu, Yi L <yi.l.liu@xxxxxxxxx>
> > > > > > > Sent: Thursday, December 21, 2023 11:40 PM
> > > > > > >
> > > > > > > +    fault &= DMA_FSTS_IQE | DMA_FSTS_ITE | DMA_FSTS_ICE;
> > > > > > > +    if (fault) {
> > > > > > > +        if (fsts)
> > > > > > > +            *fsts |= fault;
> > > > > > do we expect the fault to be accumulated? otherwise it's clearer to
> > > > > > just do direct assignment instead of asking for the caller to clear
> > > > > > the variable before invocation.
> > > > > not quite get. do you mean the fault should not be cleared in the caller
> > > > > side?
> > > > I meant:
> > > >
> > > >      if (fsts)
> > > >          *fsts = fault;
> > > >
> > > > unless there is a reason to *OR* the original value.
> > > I guess no such a reason. :) let me modify it.
> > hmmm, replied too soon. The qi_check_fault() would be called multiple
> > times in one invalidation circle as qi_submit_sync() needs to see if any
> > fault happened before the hw writes back QI_DONE to the wait descriptor.
> > There can be ICE which may eventually result in ITE. So caller of
> > qi_check_fault()
> > would continue to wait for QI_DONE. So qi_check_fault() returns 0 to let
> > qi_submit_sync() go on though ICE detected. If we use '*fsts = fault;',
> > then ICE would be missed since the input fsts pointer is the same in
> > one qi_submit_sync() call.
> Is it necessary to return fault to user if qi_check_fault() return -EAGAIN and
> a restart run succeeds?

Issue a device-TLB invalidation to no response device there is possibility

will be trapped there loop for ITE , never get return.

Thanks,

Ethan

> Thanks
> Zhenzhong