linux-kernel - Re: [PATCH v6 00/20] Add VFIO mediated device support and DEV-MSI support for the idxd driver

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Date:   Wed, 2 Jun 2021 22:49:32 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     "Tian, Kevin" <kevin.tian@...el.com>
Cc:     "Jiang, Dave" <dave.jiang@...el.com>,
        "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        "kwankhede@...dia.com" <kwankhede@...dia.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "vkoul@...nel.org" <vkoul@...nel.org>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        "Dey, Megha" <megha.dey@...el.com>,
        "Pan, Jacob jun" <jacob.jun.pan@...el.com>,
        "Liu, Yi L" <yi.l.liu@...el.com>, "Lu, Baolu" <baolu.lu@...el.com>,
        "Kumar, Sanjay K" <sanjay.k.kumar@...el.com>,
        "Luck, Tony" <tony.luck@...el.com>,
        "Williams, Dan J" <dan.j.williams@...el.com>,
        "eric.auger@...hat.com" <eric.auger@...hat.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>
Subject: Re: [PATCH v6 00/20] Add VFIO mediated device support and DEV-MSI
 support for the idxd driver

On Thu, Jun 03, 2021 at 01:11:37AM +0000, Tian, Kevin wrote:

> Jason, can you clarify your attitude on mdev guid stuff? Are you 
> completely against it or case-by-case? If the former, this is a big
> decision thus it's better to have consensus with Alex/Kirti. If the
> latter, would like to hear your criteria for when it can be used
> and when not...

I dislike it generally, but it exists so <shrug>. I know others feel
more strongly about it being un-kernely and the wrong way to use sysfs.

Here I was remarking how the example in the cover letter made the mdev
part seem totally pointless. If it is pointless then don't do it.

Remember we have stripped away the actual special need to use
mdev. You don't *have* to use mdev anymore to use vfio. That is a
significant ideology change even from a few months ago.

Jason