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Re: [PATCH v6 10/13] vpci/header: reset the command register when adding devices
- To: Jan Beulich <jbeulich@xxxxxxxx>
- From: Oleksandr Andrushchenko <Oleksandr_Andrushchenko@xxxxxxxx>
- Date: Mon, 7 Feb 2022 15:59:49 +0000
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- Delivery-date: Mon, 07 Feb 2022 16:00:03 +0000
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- Thread-topic: [PATCH v6 10/13] vpci/header: reset the command register when adding devices
On 07.02.22 17:28, Jan Beulich wrote:
> On 07.02.2022 16:14, Oleksandr Andrushchenko wrote:
>> On 07.02.22 17:05, Jan Beulich wrote:
>>> On 07.02.2022 15:46, Oleksandr Andrushchenko wrote:
>>>> On 07.02.22 16:31, Jan Beulich wrote:
>>>>> But: What's still missing here then is the separation of guest and host
>>>>> views. When we set INTx behind the guest's back, it shouldn't observe the
>>>>> bit set. Or is this meant to be another (big) TODO?
>>>> But, patch [PATCH v6 09/13] vpci/header: emulate PCI_COMMAND register for
>>>> guests
>>>> already takes care of it, I mean that it will set/reset INTx for the guest
>>>> according to MSI/MSI-X. So, if we squash these two patches the whole
>>>> picture will be seen at once.
>>> Does it? I did get the impression that the guest would be able to observe
>>> the bit set even after writing zero to it (while a reason exists that Xen
>>> wants the bit set).
>> Yes, you are correct: guest might not see what it wanted to set.
>> I meant that Xen won't allow resetting INTx if it is not possible
>> due to MSI/MSI-X
>>
>> Anyways, I think squashing will be a good idea to have the relevant
>> functionality in a single change set. Will this work for you?
> It might work, but I'd prefer things which can sensibly be separate to
> remain separate.
Ok, two patches
> Jan
>
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