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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Message-ID: <07fca197-3587-a45e-640b-bab0858067e2@redhat.com>
Date:   Tue, 18 Aug 2020 19:05:16 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Jason Gunthorpe <jgg@...dia.com>
Cc:     "Tian, Kevin" <kevin.tian@...el.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        "Jiang, Dave" <dave.jiang@...el.com>,
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        "Pan, Jacob jun" <jacob.jun.pan@...el.com>,
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        "Liu, Yi L" <yi.l.liu@...el.com>, "Lu, Baolu" <baolu.lu@...el.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 18/08/20 18:49, Jason Gunthorpe wrote:
> 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.

The point of mdev is that it's not 1:1 anymore.

Paolo

> 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
>