[libvirt] [PATCH 3/3] qemu: Prohibit chaning affinity of domain process if placement is 'auto'

[Martin Kletzander]

On 10/24/2012 12:00 PM, Osier Yang wrote:
> On one hand, numad probably will manage the affinity of domain process
> dynamically in future. On the other hand, even numad won't manage it,

s/even/even if/

> it still could confusion. Let's make things simpler enough to avoid

s/could/could cause/

> the lair for now.
> ---
>  src/qemu/qemu_driver.c |    7 +++++++
>  1 files changed, 7 insertions(+), 0 deletions(-)
> 
> diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
> index 8af316f..254f191 100644
> --- a/src/qemu/qemu_driver.c
> +++ b/src/qemu/qemu_driver.c
> @@ -4204,6 +4204,13 @@ qemudDomainPinEmulator(virDomainPtr dom,
>          goto cleanup;
>      }
>  
> +    if (vm->def->placement_mode == VIR_DOMAIN_CPU_PLACEMENT_MODE_AUTO) {
> +        virReportError(VIR_ERR_OPERATION_INVALID, "%s",
> +                       _("Changing affinity for emulator thread dynamically "
> +                         "is not allowed when CPU placement is 'auto'"));
> +        goto cleanup;
> +    }
> +
>      if (virDomainLiveConfigHelperMethod(driver->caps, vm, &flags,
>                                          &persistentDef) < 0)
>          goto cleanup;
> 

We should unify if the vcpu pinning is only meant for starting the
domain or if it's mandatory for the whole time domain is running.  It is
possible now to have auto placement and pin the vcpus while the domain
is running.

If we want to disable it for emulator threads, we should also do it for
VCPU threads.  However, then decision whether we should do it at all
should not be made by me.  Anyone else has an opinion on that?

Martin