netdev - Re: [PATCH net-net 0/4] Increase the limit of tuntap queues

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Message-ID: <20141123104623.GA31915@redhat.com>
Date:	Sun, 23 Nov 2014 12:46:23 +0200
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	David Miller <davem@...emloft.net>
Cc:	pagupta@...hat.com, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, jasowang@...hat.com, dgibson@...hat.com,
	vfalico@...il.com, edumazet@...gle.com, vyasevic@...hat.com,
	hkchu@...gle.com, wuzhy@...ux.vnet.ibm.com, xemul@...allels.com,
	therbert@...gle.com, bhutchings@...arflare.com, xii@...gle.com,
	stephen@...workplumber.org, jiri@...nulli.us,
	sergei.shtylyov@...entembedded.com
Subject: Re: [PATCH net-net 0/4] Increase the limit of tuntap queues

On Wed, Nov 19, 2014 at 10:44:27PM +0200, Michael S. Tsirkin wrote:
> On Wed, Nov 19, 2014 at 03:16:28PM -0500, David Miller wrote:
> > From: Pankaj Gupta <pagupta@...hat.com>
> > Date: Tue, 18 Nov 2014 21:52:54 +0530
> > 
> > > - Accept maximum number of queues as sysctl param so that any user space 
> > >   application like libvirt can use this value to limit number of queues. Also
> > >   Administrators can specify maximum number of queues by updating this sysctl
> > >   entry.
> > 
> > This is the only part I don't like.
> > 
> > Just let whoever has privileges to configure the tun device shoot
> > themselves in the foot if they want to by configuring "too many"
> > queues.
> > 
> > If the virtual entity runs itself out of resources by doing something
> > stupid, it's purely their problem.
> 
> Well it will run host out of kernel, no?


To clarify:

At the moment attaching/detaching queues is an unpriveledged operation.

Shouldn't we worry that an application can cause large
allocations, and provide a way to limit these?

David, could you comment on this please?

> -- 
> MST
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