Re: [Qemu-ppc] [kvm-devel] [PATCH v2] kvm-ppc: halt secondary cpus when guest reset

[Alexander Graf]

On 09.01.2012, at 22:23, Scott Wood wrote:

> On 01/09/2012 01:41 AM, Liu Yu wrote:
>> When guest reset, we need to halt secondary cpus until guest kick them.
>> This already works for tcg. The patch add the support for kvm.
>> 
>> There are two cases for kvm:
>> 
>> 1. If not use in-kernel mpic. We return env->halted in
>> kvm_arch_process_async_events(), in order to tell kvm common code
>> whether we request to halt.
>> 
>> 2. If use in-kernel mpic. Even we request to halt,
>> the common code cpu_thread_is_idle() refuses to halt,
>> because if vcpu halts while use in-kernel mpic, then there's
>> no external interrupt handled in qemu to wake up the vcpu thread.
>> In this case, we set stopped to pause the sencondaries instead,
>> And resume secondaries when primary cpu access ppce500_spin.
>> 
>> Signed-off-by: Liu Yu <address@hidden>
>> ---
>> v2:
>> Add comment and modify commit log
>> 
>> hw/ppce500_spin.c |    1 +
>> target-ppc/kvm.c  |   15 ++++++++++++++-
>> 2 files changed, 15 insertions(+), 1 deletions(-)
>> 
>> diff --git a/hw/ppce500_spin.c b/hw/ppce500_spin.c
>> index cccd940..2b52728 100644
>> --- a/hw/ppce500_spin.c
>> +++ b/hw/ppce500_spin.c
>> @@ -112,6 +112,7 @@ static void spin_kick(void *data)
>> 
>>     env->halted = 0;
>>     env->exception_index = -1;
>> +    env->stopped = 0;
>>     qemu_cpu_kick(env);
>> }
>> 
>> diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c
>> index 429349f..b7c70e2 100644
>> --- a/target-ppc/kvm.c
>> +++ b/target-ppc/kvm.c
>> @@ -504,7 +504,20 @@ void kvm_arch_post_run(CPUState *env, struct kvm_run 
>> *run)
>> 
>> int kvm_arch_process_async_events(CPUState *env)
>> {
>> -    return 0;
>> +    if (kvm_irqchip_in_kernel()) {
>> +        if (env->halted == 1 && env->exception_index == EXCP_HLT) {
>> +            /* We're here because secondary vcpus are requested to halt
>> +             * before get kicked. But it's not allowed to halt vcpu when
>> +             * kvm_irqchip_in_kernel() is true. Instead, set stopped=1
>> +             * so that vcpu thread can be paused until guest kick them */
>> +            env->stopped = 1;
>> +            return 1;
>> +        } else {
>> +            return 0;
>> +        }
>> +    }
>> +
>> +    return env->halted;
>> }
> 
> 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.

But x86 does some weird things with an mp_state variable that I have no clue 
what it's about. Jan, do you know what's going on here?


Alex