breakage in blkfront with ring_pages > 1

[Colin Percival]

Hi all,

I'm seeing breakage with ring_pages > 1 on a blkfront; more precisely, request
#32 has a garbage response (resulting in a panic) exactly as if the dom0 thinks
we're only using a single page for the ring.  Forcing ring_pages to 1 makes the
problem go away.

Has anyone seen anything like this?  Is it possible that there's a bug in how
our blkfront negotiates the request ring?  Does anyone have ring_pages > 1 in
use?

-- 
Colin Percival
Security Officer, FreeBSD | freebsd.org | The power to serve
Founder / author, Tarsnap | tarsnap.com | Online backups for the truly paranoid