Re: megasas stops I/O when running kernel as dom0 under xen4.1/4.2

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

On 15/08/11 13:52, Andreas Olsowski wrote:
> On 08/15/2011 12:49 PM, Simon Rowe wrote:
>> I've found adding
>>
>> 	options megaraid_sas poll_mode_io=1
>>
>> makes both of the systems we're seeing this on stable.
> ive been told to try that one and it works for me too (been running test 
> io for roughly 5 minutes now).
>
> driver version
> megasas: 00.00.05.30 Tue. Jan. 4 17:00:00 PDT 2011

Hello - I am now debugging.

It seems that the megaraid_sas driver will try and use either MSI-X or
legacy PCI interrupts mode, but will never try to use MSI.  The box we
can reproduce the problem on has MSI support but not MSI-X support.

As an experiment, I put a single call to pci_enable_msi() in the
megasas_probe_one() function, immediately after pci_set_master().  I now
cannot reproduce the problem.

Do any of the boxes you have which reproduce the problem set up MSI-X
interrupts for the megasas driver, or are they all using legacy PCI
interrupts?

(I am also emailing an LSI contact asking why they do not use MSI
interrupts)

~Andrew

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