linux-kernel - Re: [PATCH RFC v2 00/18] Add VFIO mediated device support and DEV-MSI support for the idxd driver

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Date:   Tue, 18 Aug 2020 13:49:03 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
CC:     "Tian, Kevin" <kevin.tian@...el.com>,
        Alex Williamson <alex.williamson@...hat.com>,
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Subject: Re: [PATCH RFC v2 00/18] Add VFIO mediated device support and
 DEV-MSI support for the idxd driver

On Tue, Aug 18, 2020 at 06:27:21PM +0200, Paolo Bonzini wrote:
> On 18/08/20 13:50, Jason Gunthorpe wrote:
> > For instance, what about suspend/resume of containers using idxd?
> > Wouldn't you want to have the same basic approach of controlling the
> > wq from userspace that virtualization uses?
> 
> The difference is that VFIO more or less standardizes the approach you
> use for live migration.  With another interface you'd have to come up
> with something for every driver, and add support in CRIU for every
> driver as well.

VFIO is very unsuitable for use as some general userspace. It only 1:1
with a single process and just can't absorb what the existing idxd
userspace is doing.

So VFIO is already not a solution for normal userspace idxd where CRIU
becomes interesting. Not sure what you are trying to say?

My point was the opposite, if you want to enable CRIU for idxd then
you probably need all the same stuff as for qemu/VFIO except in the
normal idxd user API.

Jason