Re: [Xen-devel] [PATCH] pci: clear host_maskall field on assign

[Jan Beulich <jbeulich@xxxxxxxx>]

On 08.10.2019 16:16, Roger Pau Monné  wrote:
> On Tue, Oct 08, 2019 at 03:32:25PM +0200, Jan Beulich wrote:
>> On 08.10.2019 15:14, Roger Pau Monné  wrote:
>>> On Tue, Oct 08, 2019 at 01:28:49PM +0200, Jan Beulich wrote:
>>>> On 08.10.2019 13:09, Roger Pau Monné  wrote:
>>>>> Given that as you correctly point out maskall is unset after device
>>>>> reset, I feel that option 4 is the best one since it matches the state
>>>>> of the hardware after reset.
>>>>
>>>> Right, that's the variant coming closest to what hardware state
>>>> ought to be at that point. We'd need to double check that the
>>>> per-entry mask bits are all set at that point.
>>>
>>> I'm not saying such check is not worth doing, but why do it in this
>>> case but not when also clearing the maskall (in msix_capability_init)
>>> when called from prepare_msix?
>>
>> By "double check" I meant inspect the source, not to add checking logic.
> 
> Oh, I implied you wanted to iterate over all entries and check that
> the mask bit is set for each.
> 
> It's my understanding that Xen relies on dom0 having done a device
> reset before it being assigned, which masks all entries. I've checked
> the pciback code and the reset is performed when the device is
> assigned to dom0 (ie: guest shutdown or hot-unplug), and hence when
> the device is assigned to a different domain the state of it should be
> the after reset one.
> 
> I can add a comment in assign_device that Xen expects the device state
> to be the after reset one, and hence host_maskall = guest_maskall =
> false and all entries should have the mask bit set.

Yes please.

Jan

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