Hi Alex, Eric,
> -----Original Message-----
> From: Qemu-devel [mailto:qemu-devel-
> bounces+bharat.bhushan=nxp....@nongnu.org] On Behalf Of Bharat
> Bhushan
> Sent: Friday, October 06, 2017 9:16 AM
> To: Auger Eric <eric.au...@redhat.com>; Linu Cherian
> <linuc.dec...@gmail.com>
> Cc: peter.mayd...@linaro.org; kevin.t...@intel.com; m...@redhat.com;
> marc.zyng...@arm.com; t...@semihalf.com; will.dea...@arm.com;
> drjo...@redhat.com; qemu-devel@nongnu.org;
> alex.william...@redhat.com; qemu-...@nongnu.org;
> linu.cher...@cavium.com; eric.auger....@gmail.com;
> robin.mur...@arm.com; christoffer.d...@linaro.org;
> bharatb.ya...@gmail.com
> Subject: Re: [Qemu-devel] [Qemu-arm] [PATCH v4 0/5] virtio-iommu: VFIO
> integration
>
>
>
> > >> Thanks
> > >>
> > >> Eric
> > >>>
> > >>> However you should be allowed to map 1 sg element of 5 pages and
> > >>> then notify the host about this event I think. Still looking at the
> > >>> code...
> > >>>
> > >>> I still can't reproduce the issue at the moment. What kind of
> > >>> device are you assigning?
> > >>>
> > >>> Thanks
> > >>>
> > >>> Eric
> > >>>>
> > >>>> Atleast vfio_get_vaddr called from vfio_iommu_map_notify in Qemu
> > >>>> expects the map size to be a power of 2.
> > >
> > > Actually I missed the most important here ;-)
> > >>>>
> > >>>> if (len & iotlb->addr_mask) {
> > > This check looks suspiscious to me. In our case the len is not
> > > modified by the previous translation and it fails, I don't see why.
> > > It should be valid to be able to notify 5 granules.
> >
> > So after discussion with Alex, looks the way we notify the host
> > currently is wrong. we set the addr_mask to the mapping/unmapping size
> > -1 whereas this should be a page mask instead (granule size or block size?).
> > So if the guest maps 5 x 4kB pages we should send 5 notifications for
> > each page and not a single one. It is unclear to me if we can notify
> > with hugepage/block page size mask. Peter may confirm/infirm this. in
> > vsmmuv3 code I notify by granule or block size.
My understanding is that host provides supported page sizes (page_size_mask),
and Size of each notification to host should be exactly best fit of supported
page-size and/or multiples of supported page-sizes.
So if guest maps 20K size (single request), and supported page size is 4K, so
we can still send one 20K size request.
Not sure I get it, why multiples of supported page-size cannot be provided in
one notification to host.
Thanks
-Bharat
> >
> > Bharat, please can you add this to your TODO list?
> >
> > Linu, thanks a lot for the time you spent debugging this issue.
> > Curiously on my side, it is really seldom hit but it is ...
>
> Thanks Linu and Eric, I added this to my todo list.
> While I am still not able to reproduce the issue. I tried with e1000 and now
> try with ixgbe device. May I know which device can be used to reproduce this
> issue?
>
> Thanks
> -Bharat
>
> >
> > Thanks!
> >
> > Eric
> > >
> > > Thanks
> > >
> > > Eric
> > >>>> error_report("iommu has granularity incompatible with target
> AS");
> > >>>> return false;
> > >>>> }
> > >>>>
> > >>>> Just trying to understand how this is not hitting in your case.
> > >>>>
> > >>>>
> > >>>
> > >>
> > >
