RE: [RFC v16 0/9] SMMUv3 Nested Stage Setup (IOMMU part)

Shameerali Kolothum Thodi
2021-12-08T13:33:30Z

> -----Original Message-----
> From: Eric Auger [mailto:eric.auger@redhat.com]
> Sent: 07 December 2021 11:06
> To: Zhangfei Gao <zhangfei.gao@linaro.org>; eric.auger.pro@gmail.com;
> iommu@lists.linux-foundation.org; linux-kernel@vger.kernel.org;
> kvm@vger.kernel.org; kvmarm@lists.cs.columbia.edu; joro@8bytes.org;
> will@kernel.org; robin.murphy@arm.com; jean-philippe@linaro.org;
> zhukeqian <zhukeqian1@huawei.com>
> Cc: alex.williamson@redhat.com; jacob.jun.pan@linux.intel.com;
> yi.l.liu@intel.com; kevin.tian@intel.com; ashok.raj@intel.com;
> maz@kernel.org; peter.maydell@linaro.org; vivek.gautam@arm.com;
> Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>;
> wangxingang <wangxingang5@huawei.com>; jiangkunkun
> <jiangkunkun@huawei.com>; yuzenghui <yuzenghui@huawei.com>;
> nicoleotsuka@gmail.com; chenxiang (M) <chenxiang66@hisilicon.com>;
> sumitg@nvidia.com; nicolinc@nvidia.com; vdumpa@nvidia.com;
> zhangfei.gao@gmail.com; lushenming@huawei.com; vsethi@nvidia.com
> Subject: Re: [RFC v16 0/9] SMMUv3 Nested Stage Setup (IOMMU part)
>
> Hi Zhangfei,
>
> On 12/7/21 11:35 AM, Zhangfei Gao wrote:
> >
> >
> > On 2021/12/7 下午6:27, Eric Auger wrote:
> >> Hi Zhangfei,
> >>
> >> On 12/3/21 1:27 PM, Zhangfei Gao wrote:
> >>> Hi, Eric
> >>>
> >>> On 2021/10/27 下午6:44, Eric Auger wrote:
> >>>> This series brings the IOMMU part of HW nested paging support
> >>>> in the SMMUv3.
> >>>>
> >>>> The SMMUv3 driver is adapted to support 2 nested stages.
> >>>>
> >>>> The IOMMU API is extended to convey the guest stage 1
> >>>> configuration and the hook is implemented in the SMMUv3 driver.
> >>>>
> >>>> This allows the guest to own the stage 1 tables and context
> >>>> descriptors (so-called PASID table) while the host owns the
> >>>> stage 2 tables and main configuration structures (STE).
> >>>>
> >>>> This work mainly is provided for test purpose as the upper
> >>>> layer integration is under rework and bound to be based on
> >>>> /dev/iommu instead of VFIO tunneling. In this version we also get
> >>>> rid of the MSI BINDING ioctl, assuming the guest enforces
> >>>> flat mapping of host IOVAs used to bind physical MSI doorbells.
> >>>> In the current QEMU integration this is achieved by exposing
> >>>> RMRs to the guest, using Shameer's series [1]. This approach
> >>>> is RFC as the IORT spec is not really meant to do that
> >>>> (single mapping flag limitation).
> >>>>
> >>>> Best Regards
> >>>>
> >>>> Eric
> >>>>
> >>>> This series (Host) can be found at:
> >>>> https://github.com/eauger/linux/tree/v5.15-rc7-nested-v16
> >>>> This includes a rebased VFIO integration (although not meant
> >>>> to be upstreamed)
> >>>>
> >>>> Guest kernel branch can be found at:
> >>>> https://github.com/eauger/linux/tree/shameer_rmrr_v7
> >>>> featuring [1]
> >>>>
> >>>> QEMU integration (still based on VFIO and exposing RMRs)
> >>>> can be found at:
> >>>>
> https://github.com/eauger/qemu/tree/v6.1.0-rmr-v2-nested_smmuv3_v10
> >>>> (use iommu=nested-smmuv3 ARM virt option)
> >>>>
> >>>> Guest dependency:
> >>>> [1] [PATCH v7 0/9] ACPI/IORT: Support for IORT RMR node
> >>> Thanks a lot for upgrading these patches.
> >>>
> >>> I have basically verified these patches on HiSilicon Kunpeng920.
> >>> And integrated them to these branches.
> >>> https://github.com/Linaro/linux-kernel-uadk/tree/uacce-devel-5.16
> >>> https://github.com/Linaro/qemu/tree/v6.1.0-rmr-v2-nested_smmuv3_v10
> >>>
> >>> Though they are provided for test purpose,
> >>>
> >>> Tested-by: Zhangfei Gao <zhangfei.gao@linaro.org>
> >> Thank you very much. As you mentioned, until we do not have the
> >> /dev/iommu integration this is maintained for testing purpose. The SMMU
> >> changes shouldn't be much impacted though.
> >> The added value of this respin was to propose an MSI binding solution
> >> based on RMRRs which simplify things at kernel level.
> >
> > Current RMRR solution requires uefi enabled,
> > and QEMU_EFI.fd  has to be provided to start qemu.
> >
> > Any plan to support dtb as well, which will be simpler since no need
> > QEMU_EFI.fd anymore.
> Yes the solution is based on ACPI IORT nodes. No clue if some DT
> integration is under work. Shameer?

There was some attempt in the past to create identity mappings using DT.
This is the latest I can find on it,
https://lore.kernel.org/linux-iommu/YTelDHx2REIIvV%2FN@orome.fritz.box/T/

Thanks,
Shameer