Re: [patch] qemu-kvm introduce -maxcpus argument

["Daniel P. Berrange" <berrange@redhat.com>]

On Fri, Jun 19, 2009 at 03:59:57PM +0200, Jes Sorensen wrote:
> Hi,
> 
> This one introduces a -maxcpus setting, allowing the user to specify
> the maximum number of vCPUs the system can have, as discussed with Gleb
> earlier in the week.

What is the maximum value for the 'maxcpus' setting for KVM ? 

libvirt currently does

    fd = open("/dev/kvm")
    r = ioctl(fd, KVM_CHECK_EXTENSION, KVM_CAP_NR_VCPUS);

to figure out what the maximum allowed vCPUs will be for KVM,
and currently it is returning 16 IIRC.

> @@ -5666,6 +5667,13 @@ int main(int argc, char **argv, char **e
>                      exit(1);
>                  }
>                  break;
> +            case QEMU_OPTION_maxcpus:
> +                max_cpus = atoi(optarg);
> +                if ((max_cpus < 1) || (max_cpus > machine->max_cpus)) {
> +                    fprintf(stderr, "Invalid number of CPUs\n");
> +                    exit(1);
> +                }
> +                break;
>  	    case QEMU_OPTION_vnc:
>                  display_type = DT_VNC;
>  		vnc_display = optarg;

This implies the limit (for x86 pc machine at least) is now 255. Is that
the correct interpretation on my part ?


Regards,
Daniel
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