On Mon, 28 Jan 2019 16:48:10 -0500 Eric Farman <farman@xxxxxxxxxxxxx> wrote: > On 01/28/2019 02:15 PM, Halil Pasic wrote: > > On Mon, 28 Jan 2019 18:09:48 +0100 > > Cornelia Huck <cohuck@xxxxxxxxxx> wrote: > I guess if > > the ssch() returns with non cc == 0 the CP_PENDING ---IRQ---> IDLE > > transition > > won't take place. And I guess the IRQ is a final one. > > Yes this is the one point I hadn't seen explicitly stated. We shouldn't > remain in state=BUSY if the ssch got cc!=0, and probably return to IDLE > when processing the failure. In Connie's response (Mon, 28 Jan 2019 > 18:24:24 +0100) to my note, she expressed some agreement to that. Yes, I think that's what should happen. > >> state for I/O) > >> (normal ssch) > >> > >> BUSY --- IO_REQ ---> return -EAGAIN, stay in BUSY > >> (user space is supposed to retry, as we'll eventually progress from > >> BUSY) > >> > >> CP_PENDING --- IO_REQ ---> return -EBUSY, stay in CP_PENDING > >> (user space is supposed to map this to the appropriate cc for the guest) > > > > From this it seems you don't intend to issue the second requested ssch() > > any more (and don't want to do any translation). Is that right? (If it > > is, that what I was asking for for a while, but then it's a pity for the > > retries.) > > > >> > >> IDLE --- ASYNC_REQ ---> IDLE > >> (user space is welcome to do anything else right away) > > > > Your idea is to not issue a requested hsch() if we think we are IDLE > > it seems. Do I understand this right? We would end up with a different > > semantic for hsch()/and csch() (compared to PoP) in the guest with this > > (AFAICT). > > > >> > >> BUSY --- ASYNC_REQ ---> return -EAGAIN, stay in BUSY > >> (user space is supposed to retry, as above) > >> > >> CP_PENDING --- ASYNC_REQ ---> return success, stay in CP_PENDING > >> (the interrupt will get us out of CP_PENDING eventually) > > > > Issue (c|h)sch() is an action that is done on this internal > > transition (within CP_PENDING). > > These three do read like CSCH/HSCH are subject to the same rules as > SSCH, when in fact they would be (among other reasons) issued to clean > up a lost interrupt from a previous SSCH. So maybe return -EAGAIN on > state=BUSY (don't race ourselves with the start), but issue to hardware > if CP_PENDING. I think there are some devices which require a certain hsch/csch sequence during device bringup, so it's not just cleaning up after a ssch. Therefore, we should always try to do the requested hsch/csch, unless things like "we're in the process of translating a cp, and can't deal with another request right now" prevent it. > > If we get an async request when state=IDLE, then maybe just issue it for > fun, as if it were an SSCH? For fun, but mainly because the guest wants it :)
