Re: [PATCH ats_vtd v5 04/22] intel_iommu: do not consider wait_desc as an invalid descriptor

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On 02/07/2024 17:29, CLEMENT MATHIEU--DRIF wrote:
> On 02/07/2024 15:33, Yi Liu wrote:
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> >
> > On 2024/7/2 13:52, CLEMENT MATHIEU--DRIF wrote:
> > > From: Clément Mathieu--Drif <clement.mathieu--drif@eviden.com>
> > >
> > > Signed-off-by: Clément Mathieu--Drif <clement.mathieu--drif@eviden.com>
> > > Reviewed-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
> > > ---
> > >    hw/i386/intel_iommu.c | 5 +++++
> > >    1 file changed, 5 insertions(+)
> > >
> > > diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
> > > index 98996ededc..71cebe2fd3 100644
> > > --- a/hw/i386/intel_iommu.c
> > > +++ b/hw/i386/intel_iommu.c
> > > @@ -3500,6 +3500,11 @@ static bool
> > > vtd_process_wait_desc(IntelIOMMUState *s, VTDInvDesc *inv_desc)
> > >        } else if (inv_desc->lo & VTD_INV_DESC_WAIT_IF) {
> > >            /* Interrupt flag */
> > >            vtd_generate_completion_event(s);
> > > +    } else if (inv_desc->lo & VTD_INV_DESC_WAIT_FN) {
> > > +        /*
> > > +         * SW = 0, IF = 0, FN = 1
> > > +         * Nothing to do as we process the events sequentially
> > > +         */
> > This code looks a bit weird. SW field does not co-exist with IF. But
> > either
> > SW or IF can co-exist with FN flag. Is it? Have you already seen a wait
> > descriptor that only has FN flag set but no SW nor IF flag?
> Yes, my test suite triggers that condition
I think it comes from the kernel function intel_drain_pasid_prq 
(https://elixir.bootlin.com/linux/latest/source/drivers/iommu/intel/svm.c#L467)
> > >        } else {
> > >            error_report_once("%s: invalid wait desc: hi=%"PRIx64",
> > > lo=%"PRIx64
> > >                              " (unknown type)", __func__, inv_desc->hi,
> > --
> > Regards,
> > Yi Liu