Re: [Qemu-devel] [PATCH v5 1/4] cpus: Define callback for QEMU "nmi" command

[Alexey Kardashevskiy <aik@ozlabs.ru>]

On 06/10/2014 09:43 PM, Cornelia Huck wrote:
> On Tue, 10 Jun 2014 16:18:00 +1000
> Alexey Kardashevskiy <aik@ozlabs.ru> wrote:
> 
>> This introduces an NMI (Non Maskable Interrupt) nmi_monitor_handler()
>> callback to the CPU class. It is called from QMP's "nmi" command and
>> performs an action required to cause debug crash dump on in-kernel
>> debugger invocation. The callback returns Error**.
>>
>> This adds support for it in qmp_inject_nmi(). Since no architecture
>> supports it at the moment, there is no change in behaviour.
>>
>> This changes inject-nmi command description for HMP and QMP.
>>
>> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
>> ---
>> Changes:
>> v5:
>> * s/given guest's (CPU|VCPU)/default CPU/
>> * nmi_monitor_handler() now returns Error**
>>
>>
>> v4:
>> * s/\<nmi\>/nmi_monitor_handler/
>>
>> v3:
>> * actual nmi() enablement moved from last patch to first patch
>> * changed description for QMP command too
>> ---
>>  cpus.c            | 9 ++++++++-
>>  hmp-commands.hx   | 6 ++----
>>  include/qom/cpu.h | 1 +
>>  qapi-schema.json  | 4 ++--
>>  qmp-commands.hx   | 3 +--
>>  5 files changed, 14 insertions(+), 9 deletions(-)
>>
>> diff --git a/cpus.c b/cpus.c
>> index dd7ac13..b9d6602 100644
>> --- a/cpus.c
>> +++ b/cpus.c
>> @@ -1495,6 +1495,13 @@ void qmp_inject_nmi(Error **errp)
>>          }
>>      }
>>  #else
>> -    error_set(errp, QERR_UNSUPPORTED);
>> +    CPUState *cs = qemu_get_cpu(monitor_get_cpu_index());
>> +    CPUClass *cc = CPU_GET_CLASS(cs);
> 
> Just wondering: Is CPU_GET_CLASS(NULL) really safe?


I expect it to assert so it is kind of safe.


> 
>> +
>> +    if (cs && cc->nmi_monitor_handler) {
> 
> Or is cs == NULL simply not possible, and the code should check for
> cc != NULL here instead?

This is definitely a mistype, I meant "if (cc &&...)"



>> +        cc->nmi_monitor_handler(cs, errp);
>> +    } else {
>> +        error_set(errp, QERR_UNSUPPORTED);
>> +    }
>>  #endif
>>  }
> 


-- 
Alexey