Re: [Qemu-devel] [PATCH 4/4] s390x/kvm: hw debugging support via guest PER facility

[Christian Borntraeger]

On 30/05/14 10:32, Alexander Graf wrote:

>> +    case KVM_HW_BP:
>> +        if (find_hw_breakpoint(arch_info->addr, -1, arch_info->type)) {
>> +            ret = EXCP_DEBUG;
>> +        }
>> +        break;
>> +    case KVM_SINGLESTEP:
>> +        if (cs->singlestep_enabled) {
>> +            ret = EXCP_DEBUG;
>> +        }
>> +        break;
>> +    default:
>> +        ret = -ENOSYS;
>> +    }
>> +
>> +    return ret;
> 
> What happens to the diag 501 now? Are we safe to just drop it?

There can only be a small number of HW breakpoints (basically only one from-to 
range on s390).
So gdb can (and will) use both (hbreak vs. break)