Re: [PATCH RFC v2 0/3] vdpa: dedicated descriptor table group

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Hi Jason,

On Mon, 2023-09-11 at 14:43 +0800, Jason Wang wrote:
> On Sat, Sep 9, 2023 at 4:45 PM Si-Wei Liu <si-wei.liu@xxxxxxxxxx> wrote:
> > 
> > Following patchset introduces dedicated group for descriptor table to
> > reduce live migration downtime when passthrough VQ is being switched
> > to shadow VQ. This RFC v2 is sent to incorporate the early feedback
> > from reviewers on the uAPI and driver API part of changes, the
> > associated driver patch set consuming ths API will come around
> > soon along with formal submission of this series.
> > 
> > Some initial performance data will be gathered using the real
> > hardware device with mlx5_vdpa. The target goal of this series is to
> > reduce the SVQ switching overhead to less than 300ms on a ~100GB
> > guest with 2 non-mq vhost-vdpa devices. The reduction in the downtime
> > is thanks to avoiding the full remap in the switching.
> > 
> > The plan of the intended driver implementation is to use a dedicated
> > group (specifically, 2 in below table) to host the descriptor tables
> > for data vqs, different from where buffer addresses are contained (in
> > group 0 as below). cvq does not have to allocate dedicated group for
> > descriptor table, so its buffers and descriptor table would always
> > belong to the same group (1 in table below).
> > 
> > 
> >               |  data vq | ctrl vq
> > ==============+==========+===========
> > vq_group      |    0     |    1
> > vq_desc_group |    2     |    1
> > 
> > 
> > ---
> > 
> > Si-Wei Liu (3):
> >   vdpa: introduce dedicated descriptor group for virtqueue
> >   vhost-vdpa: introduce descriptor group backend feature
> >   vhost-vdpa: uAPI to get dedicated descriptor group id
> 
> Looks good to me but I'd expect example implementations in the parent.
> 
We (Si-Wei and I) will send a non-RFC series with the mlx5_vdpa implementation
as soon as the submission window opens.

Can we add your Acked-by for these core patches?

Thanks,
Dragos
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