On Thu, Mar 23, 2017 at 01:37:41PM +0000, Jean-Philippe Brucker wrote: > On 22/03/17 22:53, Joerg Roedel wrote: > > That can't happen, when the device driver does its job right. It has to > > shut down the context which causes the PPR requests for the PASID on the > > device. This includes stopping the context and waiting until all PPR > > requests it sent are processed. > > By "processed", do you mean that they are committed to the IOMMU, or that > they came back with a PRG response? By processed I mean the device received a response to the request, or is at least no longer waiting for responses. > The driver might not be able to do the latter, since PCI defines two ways > of shutting down a context: > > * Either wait for all PPR requests to come back with a PRG response, > * Or send a Stop Marker PPR request and forget about it. Are you sure about the meaning of the stop-marker? Can you point me to where it is specified? I know about a different marker, which allows a device to issue several PPR requests and only get one response for all of them. The last request then has that marker set. But I am not aware (yet) of a marker with which the device says it no longer sends requests with this PASID. > My intent with passing flags to unbind() was to handle the case where VFIO > is unable to tell us whether PPRs are still being issued by the device. > But the issue seems moot to me now that I have a better understanding, as > there will be a detach_dev/attach_dev sequence before we start rebinding > PASIDs, and we can simply reset the PRI interface there (I'm currently > doing that in add_device, but I should move it.) VFIO should completly reset the device before it is re-used, so I don't think we run into problems there. Joerg
