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

From: "Michael S. Tsirkin" <[email-masked]>
Date: Sun, 23 Nov 2014 12:46:23 +0200

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 <[email-masked]>
> > 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