Re: [PATCH v4 6/9] KVM: Save/restore state of assigned PCI device

Jan Kiszka
2010-11-09T13:44:55Z

Am 09.11.2010 14:36, Avi Kivity wrote:
> On 11/09/2010 03:29 PM, Jan Kiszka wrote:
>> Am 09.11.2010 13:35, Avi Kivity wrote:
>>> On 11/08/2010 01:21 PM, Jan Kiszka wrote:
>>>> The guest may change states that pci_reset_function does not touch. So
>>>> we better save/restore the assigned device across guest usage.
>>>
>>> Why do we care? Shouldn't the next user reset the state to its taste?
>>
>> Maybe he should, but are we sure this actually happens? E.g.
>> pci_reset_function preserves the config state, thus does not remove the
>> traces of guest.
>
> Oh yes, I read the code but it didn't register. Of course this change
> is quite necessary.
>
> (I understood you to mean that the PCI 2.3 reset doesn't reset
> everything, but that isn't what you said).

What the hardware makes out of the reset is even another story. No
guarantees I bet (isn't function-level reset an optional thing anyway?).

At least I can report that I managed to kick my Intel 82577LM into limbo
land by trying to load the wrong driver in a guest - host reset was
required afterward to reclaim its functionality.

Jan

--
Siemens AG, Corporate Technology, CT T DE IT 1
Corporate Competence Center Embedded Linux