Re: [PATCH v2 6/7] iommu/vt-d: Add page request draining support

From: Lu Baolu
Date: Thu Apr 16 2020 - 04:44:14 EST


Hi Kevin,

On 2020/4/15 19:10, Tian, Kevin wrote:
the completion of above sequence ensures that previous queued
page group responses are sent out and received by the endpoint
and vice versa all in-fly page requests from the endpoint are queued
in iommu page request queue. Then comes a problem - you didn't
wait for completion of those newly-queued requests and their
responses.

I thought about this again.

We do page request draining after PASID table entry gets torn down and
the devTLB gets invalidated. At this point, if any new page request for
this pasid comes in, IOMMU will generate an unrecoverable fault and
response the device with IR (Invalid Request). IOMMU won't put this page
request into the queue. [VT-d spec 7.4.1]

Hence, we don't need to worry about the newly-queued requests here.

Best regards,
baolu