Re: xen-unstable warn_on in msi.c:636

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 29/07/11 15:29, Jan Beulich wrote:
>>>> On 30.06.11 at 15:31, George Dunlap <George.Dunlap@eu.citrix.com> wrote:
>> On Thu, Jun 30, 2011 at 1:17 PM, Jan Beulich <JBeulich@novell.com> wrote:
>>>>>> On 30.06.11 at 14:03, George Dunlap <George.Dunlap@eu.citrix.com> wrote:
>>>> Olaf / Jan / all, what do you think of the attached patch, which
>>>> teaches the MSI code how to deal with 0 pbas?
>>> No, definitely not an option. They simply must not be zero. The
>>> problem just is that the BARs for virtual functions all read as zero
>>> (and the real value must be calculated from information from the
>>> PF's config space).
>> But at the moment it IS zero, and this "real value" is simply not
>> being calculated.
>>
>> I realize this needs to be fixed the Right Way eventually, but at the
>> moment anyone who uses SRIOV will have a bunch of scary warnings which
>> they can't do anything about except ignore; and it's never a good idea
>> to condition people to ignore this kind of warning.
>>
>> If the current situation is safe enough that fixing it is a low
>> priority, then it's safe enough to remove the warnings for the time
>> being.  If it's not safe enough to remove the warnings, then it's not
>> safe enough to leave and a fix needs to be a priority.
> Attached a patch that eliminates the warnings for me (tested on a single
> system only so far). It ought to apply cleanly to current tip of -unstable.
>
> Jan

Tested on 2 Citrix SR-IOV boxes:

1) Dell R710 with igb, ixgbe and sfc virtual functions
2) Netscalar with 320 individual ixgbe virtual functions across 40 VMs

I tested against our Xen-4.1.1, but the patch applied cleanly.  There
seems no adverse affect on VF functionality.

-- 
Andrew Cooper - Dom0 Kernel Engineer, Citrix XenServer
T: +44 (0)1223 225 900, http://www.citrix.com