Bug#850425: linux-image-3.16.0-4-amd64: mpt3sas "swiotlb buffer is full" problem only under Xen

[Andy Smith <andy@strugglers.net>]

On Fri, Jan 06, 2017 at 11:37:11AM +0000, Andy Smith wrote:
> Andrew Cooper suggested trying two patches:
> > https://github.com/xenserver/linux-3.x.pg/blob/master/master/series#L613-L614

[…]

> Using a kernel built with those patches the problem has gone away for
> me and has been stable for about a month of production load.

Sarah Newman pointed me at another message from David Vrabel:

    https://lists.xenproject.org/archives/html/xen-devel/2016-01/msg03033.html

> > As a workaround, you can give dom0 more than 4 GiB and then the
> > driver will set a 64-bit DMA mask.  I don't think the memory needs
> > to populated so something like dom0_mem=2GiB,max:4GiB might work.

I've booted the stock jessie kernel with hypervisor command line
containing "dom0_mem=2GiB,max:4GiB" and have not yet been able to
induce a crash, whereas without this I can do so within seconds by
triggering a full-speed md array check. Normally I just have
"dom0_mem=2GiB".

This has been running less than 24hrs but is looking good so far.

Thanks,
Andy