On Tue, 29 Jan 2019 20:39:33 +0100 Halil Pasic <pasic@xxxxxxxxxxxxx> wrote: > On Tue, 29 Jan 2019 10:58:40 +0100 > Cornelia Huck <cohuck@xxxxxxxxxx> wrote: > > > > > > The problem I see with the let the hardware sort it out is that, for > > > > > that to work, we need to juggle multiple translations simultaneously > > > > > (or am I wrong?). Doing that does not appear particularly simple to > > > > > me. > > > > > > > > None in the first stage, at most two in the second stage, I guess. > > > > > > > > > > Expected benefit of the second stage over the first stage? (I see none.) > > > > Making something possible that is allowed by the architecture. Not > > really important, though. > > > > I had a chat with Farhan, and he suggested that by 'allowed by > architecture' you mean " You can submit a new request if the subchannel > is pending with primary, but not with secondary state." (from Message-ID: > <20190125152154.05120461.cohuck@xxxxxxxxxx>). Yes. I might have mixed things up, though. > > 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 “Function Control > (FC)” 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. That's not what I meant. The vfio-ccw driver still holds on to one cp, while a second one could be submitted. 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.
