Re: [PATCH] fix XSA-46 regression with xend/xm

[George Dunlap <george.dunlap@eu.citrix.com>]

On 24/05/13 12:41, Gordan Bobic wrote:
> On Fri, 24 May 2013 12:19:32 +0100, George Dunlap 
> <George.Dunlap@eu.citrix.com> wrote:
>> On Wed, May 22, 2013 at 9:51 PM, Gordan Bobic <gordan@bobich.net> wrote:
>>> On 05/21/2013 09:56 AM, Ian Campbell wrote:
>>>>
>>>> On Tue, 2013-05-21 at 09:40 +0100, Jan Beulich wrote:
>>>>>
>>>>> The hypervisor side changes for XSA-46 require the tool stack to now
>>>>> always map the guest pIRQ before granting access permission to the
>>>>> underlying host IRQ (GSI). This in particular requires that pciif.py
>>>>> no longer can skip this step (assuming qemu would do it) for HVM
>>>>> guests.
>>>>>
>>>>> This in turn exposes, however, an inconsistency between xend and 
>>>>> qemu:
>>>>> The former wants to always establish 1:1 mappings between pIRQ and 
>>>>> host
>>>>> IRQ (for non-MSI only of course), while the latter always wants to
>>>>> allocate an arbitrary mapping. Since the whole tool stack obviously
>>>>> should always agree on the mapping model, make libxc enforce the 1:1
>>>>> mapping as the more natural one (as well as being the one that allows
>>>>> for easier debugging, since there no need to find out the extra
>>>>> mapping). Users of libxc that want to establish a particular (rather
>>>>> than an allocated) mapping are still free to do so, as well as tool
>>>>> stacks not based on libxc wanting to implement an allocation based
>>>>> model (which is why it's not the hypervisor that's being changed to
>>>>> enforce either model).
>>>>>
>>>>> Since libxl, like xend, already uses a 1:1 model, it's unaffected by
>>>>> the libxc change (and it being unaffected by the original hypervisor
>>>>> side changes is - afaict - simply due to qemu getting spawned at a
>>>>> later point in time compared to the xend event flow).
>>>>>
>>>>> Signed-off-by: Jan Beulich <jbeulich@suse.com>
>>>>> Tested-by: Andreas Falck <falck.andreas.lists@gmail.com> (on 4.1)
>>>>> Tested-by: Gordan Bobic <gordan@bobich.net> (on 4.2)
>>>>
>>>>
>>>> In both cases tested with xend rather than xl or both?
>>>
>>>
>>> I can confirm that my VMs start fine with xl with this patch applied.
>>
>> ...and they are HVM guests with devices passed through?
>
> Yes, HVM guests with PCI passthrough NIC, VGA passthrough, and USB
> passthrough.

Great, thanks!  I'll check this off my list.

  -George