Subject: [RFC PATCH 24/30] iommu: Specify PASID state when unbinding a task

From: [email-masked] (Joerg Roedel)
Date: Thu, 23 Mar 2017 17:52:18 +0100

On Thu, Mar 23, 2017 at 03:52:14PM +0000, Jean-Philippe Brucker wrote:
> On 23/03/17 14:30, Joerg Roedel wrote:
> > Are you sure about the meaning of the stop-marker? Can you point me to
> > where it is specified?
> 
> The concept is introduced in the PCI ECN that adds PASIDs to the ATS
> specification. I have the following link, which is probably behind a
> wall:
> 
> https://pcisig.com/sites/default/files/specification_documents/ECN-PASID-ATS-2011-03-31.pdf
> 
> A Stop Marker is a PPR with flags Read=Write=0, Last=1, targeting the
> PASID that is being decommissioned. In section 4.1.2, the specifications
> details the two device-specific ways of stopping use of a PASID, with or
> without a Stop Marker. When done with a Stop Marker, the function doesn't
> have to wait for any outstanding PPR to return, the Stop Marker serves as
> a PASID barrier.

Thanks for that, I have a closer look. Is that stopper packet visible to
software (e.g. is an entry created in the queue)?

I have to check whether the AMD IOMMU makes this visible.

	Joerg