netdev - Re: [PATCH V7 vfio 00/10] Add device DMA logging support for mlx5 driver

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Date:   Thu, 8 Sep 2022 14:17:31 -0600
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Yishai Hadas <yishaih@...dia.com>
Cc:     <jgg@...dia.com>, <saeedm@...dia.com>, <kvm@...r.kernel.org>,
        <netdev@...r.kernel.org>, <kuba@...nel.org>,
        <kevin.tian@...el.com>, <joao.m.martins@...cle.com>,
        <leonro@...dia.com>, <maorg@...dia.com>, <cohuck@...hat.com>
Subject: Re: [PATCH V7 vfio 00/10] Add device DMA logging support for mlx5
 driver

On Thu, 8 Sep 2022 21:34:38 +0300
Yishai Hadas <yishaih@...dia.com> wrote:

> This series adds device DMA logging uAPIs and their implementation as
> part of mlx5 driver.
> 
> DMA logging allows a device to internally record what DMAs the device is
> initiating and report them back to userspace. It is part of the VFIO
> migration infrastructure that allows implementing dirty page tracking
> during the pre copy phase of live migration. Only DMA WRITEs are logged,
> and this API is not connected to VFIO_DEVICE_FEATURE_MIG_DEVICE_STATE.
> 
> The uAPIs are based on the FEATURE ioctl as were introduced earlier by
> the below RFC [1] and follows the notes that were discussed in the
> mailing list.
> 
> It includes:
> - A PROBE option to detect if the device supports DMA logging.
> - A SET option to start device DMA logging in given IOVAs ranges.
> - A GET option to read back and clear the device DMA log.
> - A SET option to stop device DMA logging that was previously started.
> 
> Extra details exist as part of relevant patches in the series.
> 
> In addition, the series adds some infrastructure support for managing an
> IOVA bitmap done by Joao Martins.
> 
> It abstracts how an IOVA range is represented in a bitmap that is
> granulated by a given page_size. So it translates all the lifting of
> dealing with user pointers into its corresponding kernel addresses.
> This new functionality abstracts the complexity of user/kernel bitmap
> pointer usage and finally enables an API to set some bits.
> 
> This functionality will be used as part of IOMMUFD series for the system
> IOMMU tracking.
> 
> Finally, we come with mlx5 implementation based on its device
> specification for the DMA logging APIs.
> 
> The matching qemu changes can be previewed here [2].
> They come on top of the v2 migration protocol patches that were sent
> already to the mailing list.
> 
> Note:
> - As this series touched mlx5_core parts we may need to send the
>   net/mlx5 patches as a pull request format to VFIO to avoid conflicts
>   before acceptance.
> 
> [1] https://lore.kernel.org/all/20220501123301.127279-1-yishaih@nvidia.com/T/
> [2] https://github.com/avihai1122/qemu/commits/device_dirty_tracking
> 
> Changes from V6: https://lore.kernel.org/all/20220905105852.26398-11-yishaih@nvidia.com/T/
> - Use the first two patches from the PR that was sent by Leon, no code
>   change was involved.
> - Patch #5:
> * Add a documentation note near vfio_log_ops as Alex suggested.

Pulled topic branch from Leon and applied 3-10 to the vfio next branch
for v6.1.  Thanks,

Alex