On Fri, Sep 13, 2024 at 02:33:59AM +0000, Tian, Kevin wrote: > > From: Jason Gunthorpe <jgg@xxxxxxxxxx> > > Sent: Thursday, September 12, 2024 7:08 AM > > > > On Wed, Sep 11, 2024 at 08:13:01AM +0000, Tian, Kevin wrote: > > > > > Probably there is a good reason e.g. for simplification or better > > > aligned with hw accel stuff. But it's not explained clearly so far. > > > > Probably the most concrete thing is if you have a direct assignment > > invalidation queue (ie DMA'd directly by HW) then it only applies to a > > single pIOMMU and invalidation commands placed there are unavoidably > > limited in scope. > > > > This creates a representation problem, if we have a vIOMMU that spans > > many pIOMMUs but invalidations do some subset how to do we model > > that. Just saying the vIOMMU is linked to the pIOMMU solves this > > nicely. > > > > yes that is a good reason. > > btw do we expect the VMM to try-and-fail when deciding whether a > new vIOMMU object is required when creating a new vdev? I think there was some suggestion the getinfo could return this, but also I think qemu needs to have a command line that matches physical so maybe it needs some sysfs? Jason
