On 23.08.2018 19:35, Tony Krowiak wrote: > On 08/23/2018 10:59 AM, Pierre Morel wrote: >> On 23/08/2018 15:38, David Hildenbrand wrote: >>> On 23.08.2018 15:22, Halil Pasic wrote: >>>> >>>> >>>> On 08/23/2018 02:47 PM, Pierre Morel wrote: >>>>> On 23/08/2018 13:12, David Hildenbrand wrote: >>>> [..] >>>>>>>>> >>>>>>>>> I'm confused, which 128 bit? >>>>>>>> >>>>>>>> >>>>>>>> Me too :) , I was assuming this block to be 128bit, but the qci >>>>>>>> block >>>>>>>> has 128 bytes.... >>>>>>>> >>>>>>>> And looking at arch/s390/include/asm/ap.h, there is a lot of >>>>>>>> information >>>>>>>> contained that is definitely not of interest for CPU models... >>>>>>>> >>>>>>>> I wonder if there is somewhere defined which bits are reserved for >>>>>>>> future features/facilities, compared to ap masks and such. >>>>>>>> >>>>>>>> This is really hard to understand/plan without access to >>>>>>>> documentation. >>>>>>>> >>>>>>>> You (Halil, Tony, Pier, ...) should have a look if what I described >>>>>>>> related to PQAP(QCI) containing features that should get part of >>>>>>>> the CPU >>>>>>>> model makes sense or not. For now I was thinking that there is >>>>>>>> some part >>>>>>>> inside of QCI that is strictly reserved for facilities/features >>>>>>>> that we >>>>>>>> can use. >>>> >>>> No there is no such part. The architecture documentation is quite >>>> confusing >>>> with some aspects (e.g. persistence) of how exactly some of these >>>> features >>>> work and are indicated. I'm having a hard time finding my opinion. I >>>> may >>>> end up asking some questions later, but for now i have to think first. >>>> >>>> Just one hint. There is a programming note stating that if bit 2 of the >>>> QCI block is one there is at least one AP card in the machine that >>>> actually >>>> has APXA installed. >>>> >>>> I read the architecture so that the APXA has a 'cpu part' (if we are >>>> doing APXA the cpu can't spec exception on certain bits not being zor9) >>>> and a 'card(s) part'. >>>> >>>> Since the stuff seems quite difficult to sort out properly, I ask >>>> myself >>>> are there real problems we must solve? >>>> >>>> This ultimately seems to be about the migration, right? You say >>>> 'This helps >>>> to catch nasty migration bugs (e.g. APXA suddenly disappearing).' at >>>> the very >>>> beginning of the discussion. Yes, we don't have to have an vfio_ap >>>> device, >>>> he guest can and will start looking for AP resources if >>>> only the cpu model features installed. So the guest could observe >>>> a disappearing APXA, but I don't think that would lead to problems >>>> (with >>>> Linux at least). >>>> >>>> And there ain't much AP a guest can sanely do without if no AP >>>> resources >>>> are there. >>>> >>>> I would really prefer not rushing a solution if we don't have to. >>>> >>>>> >>>>> >>>>>> >>>>>> What is apsc, qact, rc8a in the qci blocks? are the facility bits? >>>>> >>>>> Yes, facility bits concerning the AP instructions >>>>> >>>> >>>> According to the current AR document rc8a ain't a facility but bits >>>> 0-2 and 4-7 kind of are. >>>> >>> >>> Easy ( :) ) answer. Everything that is the CPU part should get into the >>> CPU model. Everything that is AP specific not. If APXA is not a CPU >>> facility, fine with me to leave it out. >>> >>> Ack to not rushing, but also ack to not leaving out important things. >>> Ack that this stuff is hard to ficure out. >> >> APXA is not a CPU part, it is a machine part (SIE) and a AP part >> (QCI,TAPQ), >> it has no influence on CPU instructions but on the AP instructions. >> Consequently, if I understood the definition correctly, it should not >> go in the CPU model. > > The APXA bit returned via the PQAP(QCI) instruction indicates the APXA > facility is > installed in the CPUs of the configuration. This means that the facility is > installed in one or more adjunct processors but not necessarily all. > Given that > it indicates a CPU property, maybe it does belong in the CPU model? > Hmmm, I tend to agree - especially as it affects SIE behavior. But as this is not a feature block (compared to what I thought), this clould be model as a CPU feature like AP. What about the other facilities? Do they smell more like AP card specific stuff? -- Thanks, David / dhildenb
