On 12/03/2013 09:09 AM, Andreas Färber wrote:
> Am 02.12.2013 18:06, schrieb Michael Tokarev:
>> 25.11.2013 07:39, Alexey Kardashevskiy wrote:
>>> Since modern POWER7/POWER8 chips can have more that 256 CPU threads
>>> (>2000 actually), remove this check from smp_parse.
>>>
>>> The CPUs number is still checked against machine->max_cpus and this check
>>> should be enough not to break other archs.
>
> "should be" is not exactly the highest level of confidence for a
> "trivial" patch... :/
>
>> []
>>> - if (max_cpus > 255) {
>>> - fprintf(stderr, "Unsupported number of maxcpus\n");
>>> - exit(1);
>>> - }
>
> I believe Eduardo touched that code last for NUMA, so let's CC him.
>
>> I don't know whenever this is actually safe. Do we have any static arrays
>> of size 255 somewhere, which will be overflowed without this check? :)
>
> s390 has the ipi_states[] array, but not fixed to that size.
s390 machines have QemuMachine::max_cpus == 255.
> x86 APIC IDs I think have or had a limitation to 255 rather than 16-bit?
> Igor?
>
> Alexey, did you actually check that, e.g., x86 machines don't break with
> 256 or 257 CPUs now?
PC_DEFAULT_MACHINE_OPTIONS sets it to 255. And I cannot find any machine
which would not define max_cpus, have I missed any?
--
Alexey
