[openib-general] has anyone tried MSI-X on Opteron?

[Eric W. Biederman]

Roland Dreier <roland at topspin.com> writes:

>     Tziporet> Hi, We are seeing problems (not getting the interrupt)
>     Tziporet> when trying to work with MSIX on Opteron with Fedora
>     Tziporet> core3.
> 
> As far as I can tell from reading the data sheet, the standard AMD
> 8131 PCI-X does not support MSI/MSI-X, so if that's what you are using
> then MSI-X will not work.  I have no information on the nForce4 or
> other Opteron PCI Express chipsets, but they should support MSI (since
> it is a mandatory part of the PCI Express spec).  The only question is
> whether they will use the same message address/contents as Intel.  If
> not then updates to the core Linux support are required.

I just did a quick look at the hypertransport spec.  The mapping
from MSI/MSI-X interrupts to native hypertransport interrupts was
defined in rev 1.05 which post-dates the 8131 by a little but
but it is certainly newer than the more recent chips.

Given that hypertransport interrupts are simply encoded as posted
write packets it may be possible to send an appropriate interrupt
even without explicit bridge support.

Anyway there looks to be sufficient information up at hypertransport.org
to code the support to code MSI/MSI-X support for the x86 devices with
a hypertransport FSB.  Which should be more then enough information to see
if the use the same message address/contents as Intel.

Eric