On Wed, Sep 21, 2016 at 10:18:00AM +0530, Bharata B Rao wrote: > CPU unplug doesn't work in TCG mode currently and causes frequent system > freeze. In addition to other potential problems, the main problem arises > of out the requirement to support synchronous removal of a CPU thread. > The CPU thread that performs the cleanup of the unplugged CPU, kicks and > waits for the unplugged CPU thread to finish. This wait never finishes in > TCG mode when the waiting thread and the unplugged CPU thread are one and > the same. > > So wait till proper MTTCG support is available before enabling > CPU unplug in TCG mode.
MTTCG seems like a very big hammer to fix this with. Surely we could
come up with a simpler interlock that would work for TCG in the
meantime.
>
> Signed-off-by: Bharata B Rao <bhar...@linux.vnet.ibm.com>
> ---
> hw/ppc/spapr.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index ca77bb0..d7864c6 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -2300,6 +2300,10 @@ static void spapr_machine_device_unplug(HotplugHandler
> *hotplug_dev,
> error_setg(errp, "CPU hot unplug not supported on this machine");
> return;
> }
> + if (!kvm_enabled()) {
> + error_setg(errp, "CPU hot unplug not supported in TCG mode");
> + return;
> + }
> spapr_core_unplug(hotplug_dev, dev, errp);
> }
> }
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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