On 2012-02-11 15:11, Blue Swirl wrote: > On Sat, Feb 11, 2012 at 14:00, Jan Kiszka <jan.kiszka@xxxxxx> wrote: >> On 2012-02-11 14:54, Blue Swirl wrote: >>> On Sat, Feb 11, 2012 at 12:43, Jan Kiszka <jan.kiszka@xxxxxx> wrote: >>>> On 2012-02-11 12:49, Andreas Färber wrote: >>>>> Am 11.02.2012 12:25, schrieb Blue Swirl: >>>>>> I think using cpu_single_env is an indication of a problem, like poor >>>>>> code, layering violation or poor API (vmport). What is your use case? >>>>> >>>>> I couldn't spot any in this series. Jan, note that any new use of env or >>>>> cpu_single_env will need to be redone when we convert to QOM CPU. >>>> >>>> cpu_single_env should have nothing to do with QOM. >>>> >>>> The ABIs of vmport and the KVM VAPI require a reference to the calling >>>> VCPU, and that's why you find tons of them in patch 5. >>> >>> Yes, this seems to be another case of a badly designed ABI. I guess >>> there is no way to change that anymore, just like vmport? >> >> Believe me, I grumbled over it more than once while porting it from >> qemu-kvm. The point is that some (Windows) VMs out there are running >> already with this option ROM loaded and working this unfortunate ABI. > > Maybe in time those could be deprecated and a ROM using a sane ABI > introduced instead. After some grace time the old ABI could be finally > removed. At some point. But now we have this interface and no other even thought out. Given that we want to provide a migration path from qemu-kvm to upstream rather sooner than later, I think there is no way around this model for a certain, not too short period. > >>> >>> Some of the cpu_single_env accesses in patch 5 could be avoided when >>> APIC is moved closer to CPU. VAPIC should be also close to APIC so it >>> should be able to access the CPU directly. In some other cases the >>> current state could be passed around instead once it is known. >> >> Some callbacks are I/O-port originated, ie. not associated with the >> per-CPU MMIO area or some MSR. So we would have to pass down the causing >> CPU to every I/O handler - not sure if that is desired... > > I meant things like vapic_enable_tpr_reporting(), current CPUState > could be passed via vapic_prepare() easily. Oh, there is in fact dead code in vapic_enable_tpr_reporting. It just iterates over all VCPUs, no need to know the current one. Jan
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