Re: [PATCH v2] intel_iommu: Allow both Status Write and Interrupt Flag in QI wait

[Yi Liu <yi.l.liu@intel.com>]

On 2025/7/15 14:11, CLEMENT MATHIEU--DRIF wrote:
> 
> 
> On 14/07/2025 11:22 pm, Konstantin Belousov wrote:
>> Caution: External email. Do not open attachments or click links, unless this email comes from a known sender and you know the content is safe.
>>
>>
>> On Mon, Jul 14, 2025 at 05:41:22PM +0100, David Woodhouse wrote:
>>> On 14 July 2025 15:28:09 GMT+01:00, Yi Liu <yi.l.liu@intel.com> wrote:
>>>> Hi David,
>>>>
>>>> On 2025/7/14 16:00, David Woodhouse wrote:
>>>>> From: David Woodhouse <dwmw@amazon.co.uk>
>>>>>
>>>>> FreeBSD does both, and this appears to be perfectly valid. The VT-d
>>>>> spec even talks about the ordering (the status write should be done
>>>>> first, unsurprisingly).
> 
> Are you talking about the ordering constraint mentioned in bullet
> "Page-request Drain (PD)"?

David is talking about the IF and SW flags. And he is correct. Spec has 
below sentence. It means a wait descriptor can have both IF and SW set
and indeed completion interrupt happens later than status write.  Let's
go on refine the patch. :)

"The invalidation completion event interrupt must push any in-flight 
invalidation completion status
writes, including status writes that may have originated from the same 
inv_wait_dsc for which the interrupt was generated."


Regards,
Yi Liu