linux-kernel - Re: [PATCH vhost v3 0/6] vdpa/mlx5: Add support for resumable vqs

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Date: Fri, 15 Dec 2023 14:10:51 +0000
From: Dragos Tatulea <dtatulea@...dia.com>
To: "virtualization@...ts.linux-foundation.org"
	<virtualization@...ts.linux-foundation.org>, "eperezma@...hat.com"
	<eperezma@...hat.com>, Gal Pressman <gal@...dia.com>, "si-wei.liu@...cle.com"
	<si-wei.liu@...cle.com>, "mst@...hat.com" <mst@...hat.com>, "leon@...nel.org"
	<leon@...nel.org>, Saeed Mahameed <saeedm@...dia.com>, "jasowang@...hat.com"
	<jasowang@...hat.com>
CC: "kvm@...r.kernel.org" <kvm@...r.kernel.org>, Parav Pandit
	<parav@...dia.com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "xuanzhuo@...ux.alibaba.com"
	<xuanzhuo@...ux.alibaba.com>
Subject: Re: [PATCH vhost v3 0/6] vdpa/mlx5: Add support for resumable vqs

On Fri, 2023-12-15 at 16:01 +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. 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].
> 
> The second part adds support for resumable vqs in the form of a device .resume
> operation but also for the .set_map call (suspend/resume device instead
> of re-creating vqs with new mappings).
> 
> The last part of the series introduces reference counting for mrs which
> is necessary to avoid freeing mkeys too early or leaking them.
> 
> * Changes in v3:
> - Dropped patches that allowed vq modification of state and addresses
>   when state is DRIVER_OK. This is not allowed by the standard.
>   Should be re-added under a vdpa feature flag.
> 
> * Changes in v2:
> - Added mr refcounting patches.
> - Deleted unnecessary patch: "vdpa/mlx5: Split function into locked and
>   unlocked variants"
> - Small print improvement in "Introduce per vq and device resume"
>   patch.
> - Patch 1/7 has been applied to mlx5-vhost branch.
> 
> [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 (6):
>   vdpa/mlx5: Expose resumable vq capability
>   vdpa/mlx5: Allow modifying multiple vq fields in one modify command
>   vdpa/mlx5: Introduce per vq and device resume
>   vdpa/mlx5: Use vq suspend/resume during .set_map
>   vdpa/mlx5: Introduce reference counting to mrs
>   vdpa/mlx5: Add mkey leak detection
> 
>  drivers/vdpa/mlx5/core/mlx5_vdpa.h |  10 +-
>  drivers/vdpa/mlx5/core/mr.c        |  69 +++++++---
>  drivers/vdpa/mlx5/net/mlx5_vnet.c  | 194 +++++++++++++++++++++++++----
>  include/linux/mlx5/mlx5_ifc.h      |   3 +-
>  include/linux/mlx5/mlx5_ifc_vdpa.h |   1 +
>  5 files changed, 239 insertions(+), 38 deletions(-)
> 

Please disregard this version. I will send a v4. Sorry about the noise.