On 23/03/17 16:52, Joerg Roedel wrote: > 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)? As far as I understand, it should be added to the queue like a normal PPR, and software should check the R/W/L flags combination. For SMMU at least, it is the same. The only difference is that when the PRI queue overflows, the SMMU would discard a Stop Marker instead of sending an automated response to the device (as it would do with others PPR that have the L flag.) Software shouldn't send a response to a Stop Marker either. Thanks, Jean-Philippe
