Re: [Xen-devel] [PATCH][XSA-126] xen: limit guest control of PCI command register

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 08.06.15 at 11:30, <mst@xxxxxxxxxx> wrote:
> What happens if you disable SERR# in the command register
> of 83:00.1?

We've just been told that with SERR not enabled in any of the
sibling endpoints the NMI still occurs. Not really surprising with
us now assuming that it's the root port that generates the SERR
in response to the UR coming back from an endpoint. But otoh
in conflict with what we see in the ITP log (where SERR clearly
is enabled on the endpoints, and the information we got says
that it _is_ disabled, not that they had to do anything to disable
it).

> 2.  Has a driver initialized this endpoint? What if you don't
>     load a driver before sending the transaction resulting in the UR?

They now tried at least without loading a driver in Dom0, which
didn't make a difference. Did you mean to also not load any driver
in the guest? Otoh I can't really see what difference this makes,
as the cleanup after the guest inside the hypervisor doesn't
really depend much on whether it actively used any of the MSI-X
entries.

Jan


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