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Re: [Qemu-arm] [Qemu-devel] [RFC v4 00/27] vSMMUv3/pSMMUv3 2 stage VFIO

From: Zhangfei Gao
Subject: Re: [Qemu-arm] [Qemu-devel] [RFC v4 00/27] vSMMUv3/pSMMUv3 2 stage VFIO integration
Date: Thu, 11 Jul 2019 09:53:35 +0800

On Mon, May 27, 2019 at 7:44 PM Eric Auger <address@hidden> wrote:
> Up to now vSMMUv3 has not been integrated with VFIO. VFIO
> integration requires to program the physical IOMMU consistently
> with the guest mappings. However, as opposed to VTD, SMMUv3 has
> no "Caching Mode" which allows easy trapping of guest mappings.
> This means the vSMMUV3 cannot use the same VFIO integration as VTD.
> However SMMUv3 has 2 translation stages. This was devised with
> virtualization use case in mind where stage 1 is "owned" by the
> guest whereas the host uses stage 2 for VM isolation.
> This series sets up this nested translation stage. It only works
> if there is one physical SMMUv3 used along with QEMU vSMMUv3 (in
> other words, it does not work if there is a physical SMMUv2).
> The series uses a new kernel user API [1], still under definition.
> - We force the host to use stage 2 instead of stage 1, when we
>   detect a vSMMUV3 is behind a VFIO device. For a VFIO device
>   without any virtual IOMMU, we still use stage 1 as many existing
>   SMMUs expect this behavior.
> - We introduce new IOTLB "config" notifiers, requested to notify
>   changes in the config of a given iommu memory region. So now
>   we have notifiers for IOTLB changes and config changes.
> - vSMMUv3 calls config notifiers when STE (Stream Table Entries)
>   are updated by the guest.
> - We implement a specific UNMAP notifier that conveys guest
>   IOTLB invalidations to the host
> - We implement a new MAP notifiers only used for MSI IOVAs so
>   that the host can build a nested stage translation for MSI IOVAs
> - As the legacy MAP notifier is not called anymore, we must make
>   sure stage 2 mappings are set. This is achieved through another
>   memory listener.
> - Physical SMMUs faults are reported to the guest via en eventfd
>   mechanism and reinjected into this latter.
> Note: The first patch is a code cleanup and was sent separately.
> Best Regards
> Eric
> This series can be found at:
> https://github.com/eauger/qemu/tree/v4.0.0-2stage-rfcv4
> Compatible with kernel series:
> [PATCH v8 00/29] SMMUv3 Nested Stage Setup
> (https://lkml.org/lkml/2019/5/26/95)

Have tested vfio mode in qemu on arm64 platform.

Tested-by: Zhangfei Gao <address@hidden>
qemu: https://github.com/eauger/qemu/tree/v4.0.0-2stage-rfcv4
kernel: https://github.com/eauger/linux/tree/v5.2-rc1-2stage-v8

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