Re: [Qemu-devel] [RFC PATCH] target-arm/psci.c: wake up sleeping CPUs (MTTCG)

["Alex Bennée" <alex.bennee@linaro.org>]

Paolo Bonzini <pbonzini@redhat.com> writes:

> On 24/06/2015 17:34, Alex Bennée wrote:
>> Testing with Alexander's bare metal syncronisation tests fails in MTTCG
>> leaving one CPU spinning forever waiting for the second CPU to wake up.
>> We simply need to poke the halt_cond once we have processed the PSCI
>> power on call.
>> 
>> Tested-by: Alex Bennée <alex.bennee@linaro.org>
>> CC: Alexander Spyridakis <a.spyridakis@virtualopensystems.com>
>> 
>> ---
>> TODO
>>   - exactly how does the vexpress wake up it's sleeping CPUs?
>> ---
>>  target-arm/psci.c | 2 ++
>>  1 file changed, 2 insertions(+)
>> 
>> diff --git a/target-arm/psci.c b/target-arm/psci.c
>> index d8fafab..661ff28 100644
>> --- a/target-arm/psci.c
>> +++ b/target-arm/psci.c
>> @@ -196,6 +196,8 @@ void arm_handle_psci_call(ARMCPU *cpu)
>>          }
>>          target_cpu_class->set_pc(target_cpu_state, entry);
>>  
>> +        qemu_cond_signal(target_cpu_state->halt_cond);
>
> That's called qemu_cpu_kick(target_cpu_state). :)  The patch should be
> acceptable now upstream, I think.

Oh so this might well fail in KVM too?

The qemu_cpu_kick does a qemu_cond_broadcast(cpu->halt_cond) which seems
a little excessive? Won't all sleeping CPUs wake up (and return to sleep)?

>
> Paolo
>
>>          ret = 0;
>>          break;
>>      case QEMU_PSCI_0_1_FN_CPU_OFF:
>> 

-- 
Alex Bennée