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

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Message-ID: <aff0361edcb0fd0c384bf297e71d25fb77570e15.camel@nvidia.com>
Date:   Sun, 3 Dec 2023 15:21:01 +0000
From:   Dragos Tatulea <dtatulea@...dia.com>
To:     "mst@...hat.com" <mst@...hat.com>
CC:     "xuanzhuo@...ux.alibaba.com" <xuanzhuo@...ux.alibaba.com>,
        Parav Pandit <parav@...dia.com>,
        "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>,
        "eperezma@...hat.com" <eperezma@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "si-wei.liu@...cle.com" <si-wei.liu@...cle.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "jasowang@...hat.com" <jasowang@...hat.com>,
        Saeed Mahameed <saeedm@...dia.com>,
        "galp@...dia.com" <galp@...dia.com>,
        "leon@...nel.org" <leon@...nel.org>
Subject: Re: [PATCH vhost 0/7] vdpa/mlx5: Add support for resumable vqs

On Sat, 2023-12-02 at 15:26 -0500, Michael S. Tsirkin wrote:
> 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?
> 
To avoid merge issues in Linus's tree in mlx5_ifc.h. The idea is the same as for
the "vq descriptor mappings" patchset [1].

Thanks,
Dragos

> > 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
>