Re: [Xen-devel] [PATCH v2] AMD/intremap: Prevent use of per-device vector maps until irq logic is fixed

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 03/06/13 16:28, Jan Beulich wrote:
>>>> On 03.06.13 at 17:17, Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote:
>> On 03/06/13 16:01, Jan Beulich wrote:
>>>>>> On 03.06.13 at 16:35, Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote:
>>>> As I said, this reverts to the behaviour before XSA-36, but without the
>>>> security issue of a single IOMMU interrupt remapping table.  Before
>>>> XSA-36, all AMD systems were limited in vector range because of the
>>>> global used_vector map.
>>> Right, so you'd trade one regression for another (less severe, but
>>> anyway).
>> Absolutely, especially when it comes to trying to fix a regression we
>> have pushed out in a security fix.
>>
>> Ideally a proper fix to MSI-X issue can be found, but failing a timely
>> fix, reverting to the pre XSA-36 behaviour but without the security
>> issue is a good solution.
> Just to repeat - "can be found" is the wrong term, as we already
> have a patch pending that - from all I can tell - would take care of
> the problem (and you not stating anything to the contrary makes
> me assume you agree).
>
> Jan

I would agree that it looks to fix the underlying issue.

It is however quite a large change to a subtle part of the code, which
makes me hesitant about declaring it a good backport candidate for
previous versions.

~Andrew

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