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

[Eric Auger]

Hi Nicolin,

On 11/1/24 05:09, Nicolin Chen wrote:
> Hi,
>
> This is a continued discussion following previous month's:
> https://lore.kernel.org/qemu-devel/Zvr%2Fbf7KgLN1cjOl@Asurada-Nvidia/
>
> Kernel changes are getting closer to merge, as Jason's planning to
> take vIOMMU series and smmuv3_nesting series into the iommufd tree:
> https://lore.kernel.org/all/cover.1730313494.git.nicolinc@nvidia.com/
> https://lore.kernel.org/all/cover.1730313494.git.nicolinc@nvidia.com/
> https://lore.kernel.org/all/0-v4-9e99b76f3518+3a8-smmuv3_nesting_jgg@nvidia.com/
>
> So, I think it's probably a good time to align with each others and
> talk about kicking off some QEMU upstream work in the month ahead.
>
> @Shameer,
> Do you have some update on the pluggable smmuv3 module?
>
> Updates on my side:
> 1) I have kept uAPI updated to the latest version and verified too.
>    There should be some polishing changes depending on how the basic
>    nesting infrastructure would look like from Intel/Duan's work.
> 2) I got some help from NVIDIA folks for the libvirt task. And they
>    have done some drafting and are now verifying the PCI topology
>    with "iommu=none".
>
> Once the pluggable smmuv3 module is ready to test, we will make some
> change to libvirt for that and drop the auto-assigning patches from
> the VIRT code, so as to converge for a libvirt+QEMU test.
>
> 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, yet paused for getting the vIOMMU
> series merged to this kernel cycle. I plan to continue in Nov/Dec.
> So, for the near term we will continue with the RMR solution, until
> we have something solid later.
>
> [1] https://lore.kernel.org/linux-iommu/ZrVN05VylFq8lK4q@Asurada-Nvidia/

At Red Hat we may find some cycles to resume working on the QEMU
integration. Please can you sketch some tasks we could carry out in
coordination with you and Shameer? Adding Don in the loop.

Thank you in advance

Eric
>
> Thanks
> Nicolin
>