From mboxrd@z Thu Jan 1 00:00:00 1970 From: Farhan Ali Subject: Re: [PATCH v2 2/5] vfio-ccw: concurrent I/O handling Date: Wed, 30 Jan 2019 09:32:50 -0500 Message-ID: <12c10ee1-2ef4-313f-459a-132f4e7900d8@linux.ibm.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> <20190125152154.05120461.cohuck@redhat.com> <20190125170404.28c61eab@oc2783563651> <20190128181355.2d79cae7.cohuck@redhat.com> <20190128203000.6dbf7ba3@oc2783563651> <20190129105840.1bf46c3b.cohuck@redhat.com> <20190129203933.4e57cd91@oc2783563651> <20190130142956.57f9eff3.cohuck@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable Cc: linux-s390@vger.kernel.org, Eric Farman , kvm@vger.kernel.org, Pierre Morel , qemu-s390x@nongnu.org, qemu-devel@nongnu.org, Alex Williamson To: Cornelia Huck , Halil Pasic Return-path: In-Reply-To: <20190130142956.57f9eff3.cohuck@redhat.com> Content-Language: en-US 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 01/30/2019 08:29 AM, Cornelia Huck wrote: > On Tue, 29 Jan 2019 20:39:33 +0100 > Halil Pasic wrote: >=20 >> On Tue, 29 Jan 2019 10:58:40 +0100 >> Cornelia Huck wrote: >> >>>>>> The problem I see with the let the hardware sort it out is that, f= or >>>>>> that to work, we need to juggle multiple translations simultaneous= ly >>>>>> (or am I wrong?). Doing that does not appear particularly simple t= o >>>>>> me. >>>>> >>>>> None in the first stage, at most two in the second stage, I guess. >>>>> =20 >>>> >>>> Expected benefit of the second stage over the first stage? (I see no= ne.) >>> >>> Making something possible that is allowed by the architecture. Not >>> really important, though. >>> =20 >> >> I had a chat with Farhan, and he suggested that by 'allowed by >> architecture' you mean " You can submit a new request if the subchanne= l >> is pending with primary, but not with secondary state." (from Message-= ID: >> <20190125152154.05120461.cohuck@redhat.com>). >=20 > Yes. I might have mixed things up, though. >=20 >> >> So I re-read the PoP. >> >> From the description of the start subchannel instruction: >> """ >> Special Conditions >> >> Condition code 1 is set, and no other action is >> taken, when the subchannel is status pending when >> START SUBCHANNEL is executed. On some mod- >> els, condition code 1 is not set when the subchannel >> is status pending with only secondary status; instead, >> the status-pending condition is discarded. >> >> Condition code 2 is set, and no other action is >> taken, when a start, halt, or clear function is currently >> in progress at the subchannel (see =E2=80=9CFunction Control >> (FC)=E2=80=9D on page 13). >> >> """ >> >> So I guess you mixed primary and secondary up and wanted to say: >> "You can submit a new request if the subchannel >> is pending with _secondary_, but not with _primary_ _status_." >> >> But does that really mean architecture allows the subchannel >> to accept multiple ssch() instructions so that it ends up processing >> two or more channel programs in parallel. >=20 > That's not what I meant. The vfio-ccw driver still holds on to one cp, > while a second one could be submitted. >=20 > But let's just end discussing this here, and continue with discussing > the reworked state machine, ok? It's not really relevant for going > forward with halt/clear. >=20 >=20 +1 I think we should move forward with halt/clear. Thanks Farhan