Re: [PATCH RFC v1 00/15] iommu/virtio: Nested stage support with Arm

[Vivek Kumar Gautam]

Hi Shameer,


On 1/22/21 9:19 PM, Shameerali Kolothum Thodi wrote:
> Hi Vivek,
>
> > -----Original Message-----
> > From: Vivek Kumar Gautam [mailto:vivek.gautam@xxxxxxx]
> > Sent: 21 January 2021 17:34
> > To: Auger Eric <eric.auger@xxxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx;
> > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx;
> > virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx
> > Cc: joro@xxxxxxxxxx; will.deacon@xxxxxxx; mst@xxxxxxxxxx;
> > robin.murphy@xxxxxxx; jean-philippe@xxxxxxxxxx;
> > alex.williamson@xxxxxxxxxx; kevin.tian@xxxxxxxxx;
> > jacob.jun.pan@xxxxxxxxxxxxxxx; yi.l.liu@xxxxxxxxx; lorenzo.pieralisi@xxxxxxx;
> > Shameerali Kolothum Thodi <shameerali.kolothum.thodi@xxxxxxxxxx>
> > Subject: Re: [PATCH RFC v1 00/15] iommu/virtio: Nested stage support with
> > Arm
> >
> > Hi Eric,
> >
> >
> > On 1/19/21 2:33 PM, Auger Eric wrote:
> > > Hi Vivek,
> > >
> > > On 1/15/21 1:13 PM, Vivek Gautam wrote:
> > > > This patch-series aims at enabling Nested stage translation in guests
> > > > using virtio-iommu as the paravirtualized iommu. The backend is
> > > > supported with Arm SMMU-v3 that provides nested stage-1 and stage-2
> > translation.
> > > > This series derives its purpose from various efforts happening to add
> > > > support for Shared Virtual Addressing (SVA) in host and guest. On
> > > > Arm, most of the support for SVA has already landed. The support for
> > > > nested stage translation and fault reporting to guest has been proposed [1].
> > > > The related changes required in VFIO [2] framework have also been put
> > > > forward.
> > > >
> > > > This series proposes changes in virtio-iommu to program PASID tables
> > > > and related stage-1 page tables. A simple iommu-pasid-table library
> > > > is added for this purpose that interacts with vendor drivers to
> > > > allocate and populate PASID tables.
> > > > In Arm SMMUv3 we propose to pull the Context Descriptor (CD)
> > > > management code out of the arm-smmu-v3 driver and add that as a glue
> > > > vendor layer to support allocating CD tables, and populating them with right
> > values.
> > > > These CD tables are essentially the PASID tables and contain stage-1
> > > > page table configurations too.
> > > > A request to setup these CD tables come from virtio-iommu driver
> > > > using the iommu-pasid-table library when running on Arm. The
> > > > virtio-iommu then pass these PASID tables to the host using the right
> > > > virtio backend and support in VMM.
> > > >
> > > > For testing we have added necessary support in kvmtool. The changes
> > > > in kvmtool are based on virtio-iommu development branch by
> > > > Jean-Philippe Brucker [3].
> > > >
> > > > The tested kernel branch contains following in the order bottom to
> > > > top on the git hash -
> > > > a) v5.11-rc3
> > > > b) arm-smmu-v3 [1] and vfio [2] changes from Eric to add nested page
> > > >      table support for Arm.
> > > > c) Smmu test engine patches from Jean-Philippe's branch [4]
> > > > d) This series
> > > > e) Domain nesting info patches [5][6][7].
> > > > f) Changes to add arm-smmu-v3 specific nesting info (to be sent to
> > > >      the list).
> > > >
> > > > This kernel is tested on Neoverse reference software stack with Fixed
> > > > virtual platform. Public version of the software stack and FVP is
> > > > available here[8][9].
> > > >
> > > > A big thanks to Jean-Philippe for his contributions towards this work
> > > > and for his valuable guidance.
> > > >
> > > > [1]
> > > > https://lore.kernel.org/linux-iommu/20201118112151.25412-1-eric.auger
> > > > @redhat.com/T/ [2]
> > https://lore.kernel.org/kvmarm/20201116110030.32335-12-eric.auger@red
> > > > hat.com/T/ [3]
> > > > https://jpbrucker.net/git/kvmtool/log/?h=virtio-iommu/devel
> > > > [4] https://jpbrucker.net/git/linux/log/?h=sva/smmute
> > > > [5]
> > > > https://lore.kernel.org/kvm/1599734733-6431-2-git-send-email-yi.l.liu
> > > > @intel.com/ [6]
> > > > https://lore.kernel.org/kvm/1599734733-6431-3-git-send-email-yi.l.liu
> > > > @intel.com/ [7]
> > > > https://lore.kernel.org/kvm/1599734733-6431-4-git-send-email-yi.l.liu
> > > > @intel.com/ [8]
> > > > https://developer.arm.com/tools-and-software/open-source-software/arm
> > > > -platforms-software/arm-ecosystem-fvps
> > > > [9]
> > > > https://git.linaro.org/landing-teams/working/arm/arm-reference-platfo
> > > > rms.git/about/docs/rdn1edge/user-guide.rst
> > >
> > > Could you share a public branch where we could find all the kernel pieces.
> > >
> > > Thank you in advance
> >
> > Apologies for the delay. It took a bit of time to sort things out for a public
> > branch.
> > The branch is available in my github now. Please have a look.
> >
> > https://github.com/vivek-arm/linux/tree/5.11-rc3-nested-pgtbl-arm-smmuv3-vi
> > rtio-iommu
>  > Thanks for this. Do you have a corresponding kvmtool branch mentioned 
above as public?

Thanks for showing interest. I will publish the kvmtool branch asap. 
Though the current development is based on Jean's branch for 
virtio-iommu [1], I plan to rebase the changes to master soon.

Thanks & regards
Vivek

[1] https://jpbrucker.net/git/kvmtool/log/?h=virtio-iommu/devel
> Thanks,
> Shameer