Re: nested-smmuv3 topic for QEMU/libvirt, Nov 2024

[Zhangfei Gao]

On Mon, 2 Dec 2024 at 16:07, Shameerali Kolothum Thodi
<shameerali.kolothum.thodi@huawei.com> wrote:
>
>
>
> > -----Original Message-----
> > From: Zhangfei Gao <zhangfei.gao@linaro.org>
> > Sent: Monday, December 2, 2024 6:05 AM
> > To: Jason Gunthorpe <jgg@nvidia.com>
> > Cc: Nicolin Chen <nicolinc@nvidia.com>; Shameerali Kolothum Thodi
> > <shameerali.kolothum.thodi@huawei.com>; Eric Auger
> > <eric.auger@redhat.com>; Mostafa Saleh <smostafa@google.com>; qemu-
> > arm@nongnu.org; qemu-devel@nongnu.org; Peter Maydell
> > <peter.maydell@linaro.org>; Jean-Philippe Brucker <jean-
> > philippe@linaro.org>; Moritz Fischer <mdf@kernel.org>; Michael Shavit
> > <mshavit@google.com>; Andrea Bolognani <abologna@redhat.com>;
> > Michael S. Tsirkin <mst@redhat.com>; Peter Xu <peterx@redhat.com>;
> > nathanc@nvidia.com; arighi@nvidia.com; ianm@nvidia.com;
> > jan@nvidia.com; mochs@nvidia.com
> > Subject: Re: nested-smmuv3 topic for QEMU/libvirt, Nov 2024
> >
> > Hi, Nico
> >
> > On Fri, 1 Nov 2024 at 19:55, Jason Gunthorpe <jgg@nvidia.com> wrote:
> > >
> > > On Thu, Oct 31, 2024 at 09:09:20PM -0700, Nicolin Chen wrote:
> > >
> > > > FWIW, Robin requested a different solution for MSI mapping [1], v.s.
> > > > the RMR one that we have been using since Eric's work. I drafted a
> > > > few VFIO/IOMMUFD patches for that,
> > >
> > > I also talked to MarcZ about this at LPC and he seems willing to
> > > consider it. It took a bit to explain everything though. So I think we
> > > should try in Nov/Dec
> >
> > When boot qemu, reports this
> >
> > qemu-system-aarch64: warning: IOMMU_IOAS_MAP failed: Bad address, PCI
> > BAR?
> > qemu-system-aarch64: vfio_container_dma_map(0xaaaadd30f110,
> > 0x8000200000, 0x10000, 0xffffb8031000) = -14 (Bad address)
> > qemu-system-aarch64: warning: IOMMU_IOAS_MAP failed: Bad address, PCI
> > BAR?
> > qemu-system-aarch64: vfio_container_dma_map(0xaaaadd2bc310,
> > 0x8000200000, 0x10000, 0xffffb8031000) = -14 (Bad address)
> > qemu-system-aarch64: warning: IOMMU_IOAS_MAP failed: Bad address, PCI
> > BAR?
> > qemu-system-aarch64: vfio_container_dma_map(0xaaaadcf90000,
> > 0x8000200000, 0x10000, 0xffffb8031000) = -14 (Bad address)
> >
> > Will this also be solved in the new MSI mapping patchset?
>
> Nope. These are not related to MSIs. These mappings are required for
> P2P DMA between devices and is not supported by IOMMUFD at the moment.
>
> See the discussion here,
> https://lore.kernel.org/all/20220426103507.5693a0ca.alex.williamson@redhat.com/

Thanks Shameer