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

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Message-ID: <7763531a-625d-10c6-c35e-2ce41e75f606@redhat.com>
Date:   Tue, 7 Dec 2021 11:27:41 +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 12/3/21 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.

Thanks!

Eric
>
> Thanks
>