From mboxrd@z Thu Jan 1 00:00:00 1970 From: Cornelia Huck Subject: Re: [PATCH v2 2/5] vfio-ccw: concurrent I/O handling Date: Fri, 25 Jan 2019 15:21:54 +0100 Message-ID: <20190125152154.05120461.cohuck@redhat.com> References: <20190121110354.2247-1-cohuck@redhat.com> <20190121110354.2247-3-cohuck@redhat.com> <2dac6201-9e71-b188-0385-d09d05071a1c@linux.ibm.com> <5627cb78-22b3-0557-7972-256bc9560d86@linux.ibm.com> <20190125112437.2c06fac6.cohuck@redhat.com> <20190125135835.2d59b511.cohuck@redhat.com> <20190125150101.3b61f0a1@oc2783563651> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: linux-s390@vger.kernel.org, Eric Farman , Alex Williamson , Pierre Morel , kvm@vger.kernel.org, Farhan Ali , qemu-devel@nongnu.org, qemu-s390x@nongnu.org To: Halil Pasic Return-path: In-Reply-To: <20190125150101.3b61f0a1@oc2783563651> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+gceq-qemu-devel2=m.gmane.org@nongnu.org Sender: "Qemu-devel" List-Id: kvm.vger.kernel.org On Fri, 25 Jan 2019 15:01:01 +0100 Halil Pasic wrote: > On Fri, 25 Jan 2019 13:58:35 +0100 > Cornelia Huck wrote: > > - We currently do not want the user space to submit another channel > > program while the first one is still in flight. As submitting another > > one is a valid request, however, we should allow this in the future > > (once we have the code to handle that in place). > > I don't agree. There is at most one channel program processed by a > subchannel at any time. I would prefer an early error code if channel > programs are issued on top of each other (our virtual subchannel > is channel pending or FC start function bit set or similar). You can submit a new request if the subchannel is pending with primary, but not with secondary state. Regardless of that, I think it is much easier to push as much as possible of sorting out of requests to the hardware.