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Re: [PATCH v10 00/10] virtio-iommu: VFIO integration

From: Auger Eric
Subject: Re: [PATCH v10 00/10] virtio-iommu: VFIO integration
Date: Fri, 16 Oct 2020 15:13:08 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0

Hi Jean,

On 10/8/20 7:15 PM, Jean-Philippe Brucker wrote:
> This series adds support for VFIO endpoints to virtio-iommu.
> Versions 1 to 9 were posted by Bharat Bhushan, but I am taking over for
> now since he doesn't have much time to spend on it. Thanks again Bharat
> for the work!
> Two major changes since [v9]:
> * Don't use per-endoint page_size_mask properties. Instead keep a global
>   page size for the virtio-iommu device, updated when adding a VFIO
>   endpoint. Reject hotplug if the page size is incompatible.
> * Try to make the MAP/UNMAP paths more efficient, by keeping track of
>   memory region within the endpoint structure.
> More testing would be appreciated, since I can only test using a software
> model as host at the moment. But it does seem to hold well with PCIe
> hotplug/unplug, and pass-through to guest userspace, which are no mean
> feat.

I tested vhost migration and the following configurations:
host 4K- guest 4K: vhost, vfio, vfio hotplug
host 64K - guest 64K: vhost, vfio, vfio hotplug
host 4K - guest 64K: vhost, vfio, vfio hoplug

All those configs worked for me. I haven't noticed any isse with those.


> Note that one page size combination is not supported: host 64kB guest
> 4kB cannot work, because the host IOMMU driver will automatically pick
> 64kB pages which prevents mapping at a smaller granule. Supporting this
> case would require introducing a page size negotiation mechanism from
> the guest all the way to the host IOMMU driver. Possible, but not
> planned at the moment.
> [v9] 
> https://lore.kernel.org/qemu-devel/20200323084617.1782-1-bbhushan2@marvell.com/
> Bharat Bhushan (7):
>   virtio-iommu: Add memory notifiers for map/unmap
>   virtio-iommu: Call memory notifiers in attach/detach
>   virtio-iommu: Add replay() memory region callback
>   virtio-iommu: Add notify_flag_changed() memory region callback
>   memory: Add interface to set iommu page size mask
>   vfio: Set IOMMU page size as per host supported page size
>   virtio-iommu: Set supported page size mask
> Jean-Philippe Brucker (3):
>   virtio-iommu: Fix virtio_iommu_mr()
>   virtio-iommu: Store memory region in endpoint struct
>   vfio: Don't issue full 2^64 unmap
>  include/exec/memory.h    |  26 +++++
>  hw/vfio/common.c         |  19 ++++
>  hw/virtio/virtio-iommu.c | 204 ++++++++++++++++++++++++++++++++++++++-
>  softmmu/memory.c         |  13 +++
>  hw/virtio/trace-events   |   5 +
>  5 files changed, 265 insertions(+), 2 deletions(-)

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