RE: [PATCH v5 00/19] Add vfio_device cdev for iommufd support

Shameerali Kolothum Thodi
2023-03-08T16:11:17Z

> -----Original Message-----
> From: Nicolin Chen [mailto:nicolinc@nvidia.com]
> Sent: 04 March 2023 07:01
> To: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>
> Cc: Xu, Terrence <terrence.xu@intel.com>; Liu, Yi L <yi.l.liu@intel.com>;
> Jason Gunthorpe <jgg@nvidia.com>; alex.williamson@redhat.com; Tian,
> Kevin <kevin.tian@intel.com>; joro@8bytes.org; robin.murphy@arm.com;
> cohuck@redhat.com; eric.auger@redhat.com; kvm@vger.kernel.org;
> mjrosato@linux.ibm.com; chao.p.peng@linux.intel.com;
> yi.y.sun@linux.intel.com; peterx@redhat.com; jasowang@redhat.com;
> lulu@redhat.com; suravee.suthikulpanit@amd.com;
> intel-gvt-dev@lists.freedesktop.org; intel-gfx@lists.freedesktop.org;
> linux-s390@vger.kernel.org; Hao, Xudong <xudong.hao@intel.com>; Zhao,
> Yan Y <yan.y.zhao@intel.com>
> Subject: Re: [PATCH v5 00/19] Add vfio_device cdev for iommufd support
>
> On Fri, Mar 03, 2023 at 03:01:03PM +0000, Shameerali Kolothum Thodi
> wrote:
> > External email: Use caution opening links or attachments
> >
> >
> > > -----Original Message-----
> > > From: Nicolin Chen [mailto:nicolinc@nvidia.com]
> > > Sent: 02 March 2023 23:51
> > > To: Shameerali Kolothum Thodi
> <shameerali.kolothum.thodi@huawei.com>
> > > Cc: Xu, Terrence <terrence.xu@intel.com>; Liu, Yi L
> > > <yi.l.liu@intel.com>; Jason Gunthorpe <jgg@nvidia.com>;
> > > alex.williamson@redhat.com; Tian, Kevin <kevin.tian@intel.com>;
> > > joro@8bytes.org; robin.murphy@arm.com; cohuck@redhat.com;
> > > eric.auger@redhat.com; kvm@vger.kernel.org; mjrosato@linux.ibm.com;
> > > chao.p.peng@linux.intel.com; yi.y.sun@linux.intel.com;
> > > peterx@redhat.com; jasowang@redhat.com; lulu@redhat.com;
> > > suravee.suthikulpanit@amd.com; intel-gvt-dev@lists.freedesktop.org;
> > > intel-gfx@lists.freedesktop.org; linux-s390@vger.kernel.org; Hao,
> > > Xudong <xudong.hao@intel.com>; Zhao, Yan Y <yan.y.zhao@intel.com>
> > > Subject: Re: [PATCH v5 00/19] Add vfio_device cdev for iommufd
> > > support
> > >
> > > On Thu, Mar 02, 2023 at 09:43:00AM +0000, Shameerali Kolothum Thodi
> > > wrote:
> > >
> > > > Hi Nicolin,
> > > >
> > > > Thanks for the latest ARM64 branch. Do you have a working Qemu
> > > > branch
> > > corresponding to the
> > > > above one?
> > > >
> > > > I tried the
> > >
> https://github.com/nicolinc/qemu/tree/wip/iommufd_rfcv3%2Bnesting%2B
> > > smmuv3
> > > > but for some reason not able to launch the Guest.
> > > >
> > > > Please let me know.
> > >
> > > I do use that branch. It might not be that robust though as it went
> > > through a big rebase.
> >
> > Ok. The issue seems to be quite random in nature and only happens when
> > there are multiple vCPUs. Also doesn't look like related to VFIO
> > device assignment as I can reproduce Guest hang without it by only
> > having nested-smmuv3 and iommufd object.
> >
> > ./qemu-system-aarch64-iommuf -machine
> > virt,gic-version=3,iommu=nested-smmuv3,iommufd=iommufd0 \
> -enable-kvm
> > -cpu host -m 1G -smp cpus=8,maxcpus=8 \ -object iommufd,id=iommufd0
> \
> > -bios QEMU_EFI.fd \ -kernel Image-6.2-iommufd \ -initrd
> > rootfs-iperf.cpio \ -net none \ -nographic \ -append "rdinit=init
> > console=ttyAMA0 root=/dev/vda rw earlycon=pl011,0x9000000" \ -trace
> > events=events \ -D trace_iommufd
> >
> > When the issue happens, no output on terminal as if Qemu is in a locked
> state.
> >
> > Can you try with the followings?
> > >
> > > --trace "iommufd*" --trace "smmu*" --trace "vfio_*" --trace "pci_*"
> > > --trace "msi_*" --trace "nvme_*"
> >
> > The only trace events with above are this,
> >
> > iommufd_backend_connect fd=22 owned=1 users=1 (0) smmu_add_mr
> > smmuv3-iommu-memory-region-0-0
> >
> > I haven't debugged this further. Please let me know if issue is
> > reproducible with multiple vCPUs at your end. For now will focus on VFIO
> dev specific tests.
>
> Oh. My test environment has been a single-core vCPU. So that doesn't
> happen to me. Can you try a vanilla QEMU branch that our nesting branch is
> rebased on? I took a branch from Yi as the baseline, while he might take
> from Eric for the rfcv3.
>
> I am guessing that it might be an issue in the common tree.

Yes, that looks like the case.
I tried with:
commit 13356edb8750("Merge tag 'block-pull-request' of https://gitlab.com/stefanha/qemu into staging")

And issue is still there. So hopefully once we rebase everything it will go away.

Thanks,
Shameer