Re: [virtio-comment] RE: [PATCH v13] virtio-net: support the virtqueue coalescing moderation

From: "Michael S. Tsirkin" <mst@redhat.com>
To: Parav Pandit <parav@nvidia.com>
Cc: Cornelia Huck <cohuck@redhat.com>,
	Heng Qi <hengqi@linux.alibaba.com>,
	"virtio-dev@lists.oasis-open.org"
	<virtio-dev@lists.oasis-open.org>,
	"virtio-comment@lists.oasis-open.org"
	<virtio-comment@lists.oasis-open.org>,
	Jason Wang <jasowang@redhat.com>,
	Alvaro Karsz <alvaro.karsz@solid-run.com>,
	David Edmondson <david.edmondson@oracle.com>,
	Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Subject: Re: [virtio-comment] RE: [PATCH v13] virtio-net: support the virtqueue coalescing moderation
Date: Wed, 22 Mar 2023 12:50:44 -0400	[thread overview]
Message-ID: <20230322124843-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <PH0PR12MB5481F9FF6580D1F8847B9D3BDC869@PH0PR12MB5481.namprd12.prod.outlook.com>

On Wed, Mar 22, 2023 at 04:46:36PM +0000, Parav Pandit wrote:
> 
> > From: Cornelia Huck <cohuck@redhat.com>
> > Sent: Wednesday, March 22, 2023 12:44 PM
> > 
> > >> Well, I think we want to avoid having to add a normative statement
> > >> for the device, so we need to be strict with what the driver is allowed to do.
> > > Drivers are untrusted entities.
> > > device normative statement is needed, it will do the checks anyway where it
> > is applying the config.
> > 
> > But isn't that implementation specific? I.e. if the driver sends junk, the device
> > needs to be able to deal with it in any case.
> Not sure which part is implementation specific.
> The device will deal with it and return an error code when supplied qid is invalid (of cvq or of disabled vq).

spec currently defines, generally, how devices behave if driver matches
spec. We do not generally specify what happens if driver is out of spec.
For example it's ok for device to just get wedged until reset.
It's doable to change this but if yes we should do it over the board.
And the benefit, IMHO, is limited.
And doing it just for the coalescing commands would be super weird.

-- 
MST

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