On Mon, 20 Apr 2020 14:13:17 +0200 Cornelia Huck <cohuck@xxxxxxxxxx> wrote: > > Remove the explicit prefetch check when using vfio-ccw devices. > > This check is not needed as all Linux channel programs are intended > > to use prefetch and will be executed in the same way regardless. > > Hm... my understanding is that we have the reasonable expectation that > our guests will always issue channel programs that work fine with > prefetch even if the bit is not set in the orb (including CCW IPL, in > the way it is implemented in the s390-ccw QEMU bios), and therefore > this patch is just making things less complicated. AFAIR the problem is not s390-ccw QEMU bios. We could easily fix that. The practical problem is some channel programs generated by zipl that simply fail to set the bit (although they could). That is a perfectly legit thing to do, because the prefetch bit was originally about performance. Sorry I missed your mail, so complained about the same issues. Regards, Halil
