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

[Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>]

> -----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.

Thanks,
Shameer