On 09/11/16 14:39, Boris Ostrovsky wrote:
> This domctl is called when a VCPU is hot-(un)plugged to a guest (via
> 'xl vcpu-set'). While this currently is only intended to be needed by
> PVH guests we will call this domctl for all (x86) guests for consistency.
>
> Signed-off-by: Boris Ostrovsky <boris.ostrov...@oracle.com>
> Acked-by: Daniel De Graaf <dgde...@tycho.nsa.gov>
> ---
> Changes in v2:
> * Added comment in arch_do_domctl() stating that the domctl is only required
> for PVH guests
I am not happy with this change until we understand why it is needed.
Are we genuinely saying that there is no current enforcement in the
PV-hotplug mechanism?
> diff --git a/xen/arch/x86/domctl.c b/xen/arch/x86/domctl.c
> index 2a2fe04..b736d4c 100644
> --- a/xen/arch/x86/domctl.c
> +++ b/xen/arch/x86/domctl.c
> @@ -1430,6 +1430,23 @@ long arch_do_domctl(
> }
> break;
>
> + case XEN_DOMCTL_set_avail_vcpus:
> + {
> + unsigned int num = domctl->u.avail_vcpus.num;
> +
> + /*
> + * This is currently only needed by PVH guests (but
> + * any guest is free to make this call).
> + */
> + ret = -EINVAL;
> + if ( num > d->max_vcpus )
> + break;
> +
> + d->arch.avail_vcpus = num;
> + ret = 0;
> + break;
> + }
What do you actually mean by "avail_vcpus"? What happens if a vcpu
higher than the new number is currently online and running? What
happens to the already-existing vcpus-at-startup value?
~Andrew
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