Am 12.09.18 um 19:42 schrieb Tony Krowiak: > On 08/23/2018 04:24 AM, Cornelia Huck wrote: >> On Thu, 23 Aug 2018 09:48:48 +0200 >> David Hildenbrand <david@xxxxxxxxxx> wrote: >> >>>> Migration of AP devices is not supported by this patch series, so this >>>> should >>>> not be an issue. >>> Might not be a problem now, but could be later. As I said in a different >>> reply, the CPU model in QEMU does not care about KVM. >>> >>> I want the QEMU CPU model and the KVM interfaces to be clean and future >>> proof. That's why my opinion is to handle PQAP(QCI) just like all the >>> other "feature blocks" we already have. >> +1 to that sentiment. >> >> It's better to try to get this correct now than having to hack around >> should we want to implement things in the future. > > Just so we're on the same page here as far as what to expect for v10 of > this patch series, let me summarize the the very long series of private > exchanges as well as this thread: > > * The APXA facility indicated by a bit returned in the response to the > PQAP(QCI) function indicates only whether the APXA facility is available > on one or more APs installed on the system. > * The only way to change the bit returned from PQAP(QCI) is to intercept the > instruction and emulate it, so it makes no sense for passthrough devices. > * The AP(s) with APXA installed may not necessarily even be in the > configuration. > * The only way to determine whether APXA is installed in a given AP is to > query it using the PQAP(TAPQ) instruction. > > It was decided that APXA is better modeled as device configuration. If > and when > emulation is implemented, APXA can be configured for any AP devices assigned > to a guest. Since AP instructions will be intercepted when emulating AP, > the PQAP(QCI) instruction can return the APXA bit according to whether any > AP is configured with APXA installed. That matches the real architecture > much > more closely. So, the bottom line is that we will not introduce a new > CPU model > feature for APXA in v10 of this series. Yes, that sounds sane to me. In addition, all other QCI indicated "features/facilitites" are handled on a per-device basis and not on a CPU-model basis. -- Thanks, David / dhildenb
