linux-kernel - Re: [PATCH vhost 0/7] vdpa/mlx5: Add support for resumable vqs

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Date:   Sat, 2 Dec 2023 15:26:05 -0500
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Dragos Tatulea <dtatulea@...dia.com>
Cc:     Jason Wang <jasowang@...hat.com>,
        Eugenio Perez Martin <eperezma@...hat.com>,
        Si-Wei Liu <si-wei.liu@...cle.com>,
        Saeed Mahameed <saeedm@...dia.com>,
        Leon Romanovsky <leon@...nel.org>,
        virtualization@...ts.linux-foundation.org, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Gal Pressman <galp@...dia.com>,
        Parav Pandit <parav@...dia.com>,
        Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Subject: Re: [PATCH vhost 0/7] vdpa/mlx5: Add support for resumable vqs

On Fri, Dec 01, 2023 at 12:48:50PM +0200, Dragos Tatulea wrote:
> Add support for resumable vqs in the driver. This is a firmware feature
> that can be used for the following benefits:
> - Full device .suspend/.resume.
> - .set_map doesn't need to destroy and create new vqs anymore just to
>   update the map. When resumable vqs are supported it is enough to
>   suspend the vqs, set the new maps, and then resume the vqs.
> 
> The first patch exposes the relevant bits in mlx5_ifc.h. That means it
> needs to be applied to the mlx5-vhost tree [0] first.

I didn't get this. Why does this need to go through that tree?
Is there a dependency on some other commit from that tree?

> Once applied
> there, the change has to be pulled from mlx5-vhost into the vhost tree
> and only then the remaining patches can be applied. Same flow as the vq
> descriptor mappings patchset [1].
> 
> To be able to use resumable vqs properly, support for selectively modifying
> vq parameters was needed. This is what the middle part of the series
> consists of.
> 
> [0] https://git.kernel.org/pub/scm/linux/kernel/git/mellanox/linux.git/log/?h=mlx5-vhost
> [1] https://lore.kernel.org/virtualization/20231018171456.1624030-2-dtatulea@nvidia.com/
> 
> Dragos Tatulea (7):
>   vdpa/mlx5: Expose resumable vq capability
>   vdpa/mlx5: Split function into locked and unlocked variants
>   vdpa/mlx5: Allow modifying multiple vq fields in one modify command
>   vdpa/mlx5: Introduce per vq and device resume
>   vdpa/mlx5: Mark vq addrs for modification in hw vq
>   vdpa/mlx5: Mark vq state for modification in hw vq
>   vdpa/mlx5: Use vq suspend/resume during .set_map
> 
>  drivers/vdpa/mlx5/core/mr.c        |  31 +++---
>  drivers/vdpa/mlx5/net/mlx5_vnet.c  | 172 +++++++++++++++++++++++++----
>  include/linux/mlx5/mlx5_ifc.h      |   3 +-
>  include/linux/mlx5/mlx5_ifc_vdpa.h |   4 +
>  4 files changed, 174 insertions(+), 36 deletions(-)
> 
> -- 
> 2.42.0