linux-kernel - Re: [RFC v16 0/9] SMMUv3 Nested Stage Setup (IOMMU part)

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Date:   Tue, 7 Dec 2021 12:06:14 +0100
From:   Eric Auger <eric.auger@...hat.com>
To:     Zhangfei Gao <zhangfei.gao@...aro.org>, eric.auger.pro@...il.com,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, kvmarm@...ts.cs.columbia.edu, joro@...tes.org,
        will@...nel.org, robin.murphy@....com, jean-philippe@...aro.org,
        zhukeqian1@...wei.com
Cc:     alex.williamson@...hat.com, jacob.jun.pan@...ux.intel.com,
        yi.l.liu@...el.com, kevin.tian@...el.com, ashok.raj@...el.com,
        maz@...nel.org, peter.maydell@...aro.org, vivek.gautam@....com,
        shameerali.kolothum.thodi@...wei.com, wangxingang5@...wei.com,
        jiangkunkun@...wei.com, yuzenghui@...wei.com,
        nicoleotsuka@...il.com, chenxiang66@...ilicon.com,
        sumitg@...dia.com, nicolinc@...dia.com, vdumpa@...dia.com,
        zhangfei.gao@...il.com, lushenming@...wei.com, vsethi@...dia.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@...aro.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?

Thanks

Eric
>
> Thanks
>
>