On 2012-01-10 18:43, Scott Wood wrote: > On 01/10/2012 03:38 AM, Jan Kiszka wrote: >> On 2012-01-10 00:17, Scott Wood wrote: >>> On 01/09/2012 04:39 PM, Alexander Graf wrote: >>>> >>>> On 09.01.2012, at 22:23, Scott Wood wrote: >>>>> Alex, is there a better way to deal with the IRQ chip issue? >>>> >>>> To be honest, I'm not sure what the issue really is. >>> >>> If irqchip is enabled, env->halted won't result in a CPU being >>> considered idle -- since QEMU won't see the interrupt that wakes the >>> vcpu, and the idling is handled in the kernel. In this case we're >>> waiting for MMIO rather than an interrupt, and it's the kernel that >>> doesn't know what's going on. >>> >>> It seems wrong to use env->stopped, though, as a spin-table release >>> should not override a user's explicit request to stop a CPU. It might >>> be OK (though a bit ugly) if the only usage of env->stopped is through >>> pause_all_vcpus(), and the boot thread is the first one to be kicked >>> (though in theory the boot cpu could wake another cpu, and that could >>> wake a cpu that comes before it, causing a race with pause_all_vcpus()). >>> >>> If it is OK to use env->stopped, is there any reason not to always use >>> it (versus just with irqchip)? >> >> Why don't you wait in the kernel with in-kernel irqchip under all >> condition (except pausing VCPUs, of course) on PPC? Just like x86 does. > > We do for normal idling. This is a bit different, in that we're not > waiting for an interrupt, but for an MMIO that releases the cpu at > boot-time.
Where is the state stored that declares a VCPU to wait for that event? Where is it set, where removed? What about implementing MP_STATE on PPC, at least those states that make sense? Don't you need that anyway for normal HALT<->RUNNABLE transitions? Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux
