Re: xsa46-4.2.patch breaks PCI passthrough?

[Steven Haigh <netwiz@crc.id.au>]

On 05/02/2013 02:07 AM, Andrew Cooper wrote:
> On 01/05/13 16:26, Steven Haigh wrote:
>> On 2/05/2013 1:18 AM, George Dunlap wrote:
>>> On Wed, May 1, 2013 at 6:29 AM, Steven Haigh <netwiz@crc.id.au> wrote:
>>>> Hi all,
>>>>
>>>> I've had a report lodged against my packages that the patch provided for
>>>> XSA46 against Xen 4.2.1 causes PCI passthru to break.
>>>>
>>>> It seems that 4.2.1 *without* the XSA46 patch works perfectly. 4.2.2 does
>>>> not work.
>>> Have you tried this with xen-unstable tip?  That would be a blocker
>>> bug for the 4.3 release.
>> Hi George,
>>
>> It hasn't been tried it against anything other than 4.2.1 & 4.2.2 as
>> yet. As I'm not the end user with the problem here, I need to wait for
>> feedback.
>>
>> I have passed the patch provided by Andrew to the bug author - when I've
>> got feedback on this I'll be able to provide more information. I think
>> when we've got a root cause for this then it should be simple to verify
>> it on 4.3.
>>
> I have been investigating this issue on XenServer.
>
> On XenServer, PCIPassthrough to a SLES11SP1 guest is working correctly,
> even with the XSA-46 patch applied.
>
> When passing through physical devices, my hypervisor debugging is being
> triggered, but the actions of XEN_DOMCTL_irq_permission appear to be
> correct, given sensible input from the Xapi toolstack.  When passing
> through an SRIOV virtual function, no hypervisor debugging is being
> triggered.
>
> At a preliminary guess, I would say that XM looks to be doing something
> stupid which it used to be getting away with, but is not now given the
> changed in the hypervisor.
>
> I suspect that it will be hard to progress this issue until Gordan
> applied my debugging patch and gets back with the results.
>
Hi Andrew,

Got a reply from Gordon -> http://xen.crc.id.au/bugs/view.php?id=5

The 'xm dmesg' output shows the following:
(XEN) sh error: sh_remove_all_mappings(): can't find all mappings of mfn 
4bc435: c=c000000000000002 t=7400000000000001
(XEN) **DBG perms { 16, 1 } = 0
(XEN) **DBG perms { 34, 1 } = -22
(XEN) sh error: sh_remove_all_mappings(): can't find all mappings of mfn 
4be230: c=c000000000000002 t=7400000000000001
(XEN) **DBG perms { 16, 1 } = 0
(XEN) **DBG perms { 34, 1 } = -22

The full dmesg is attached to the bug report.

--
Steven Haigh