On 07/20/20 16:16, Igor Mammedov wrote:
> CPU hot-unplug with SMM requires firmware participation to prevent
> guest crash (i.e. CPU can be removed only after OS _and_ firmware
> were prepared for th action).
(1) s/th action/the action/
> Previous patches introduced ICH9_LPC_SMI_F_CPU_HOT_UNPLUG_BIT
> feature bit, which is advertised by firmware when it has support
> for CPU hot-unplug. Use it to check if guest is able to handle
> unplug and make device_del fail gracefully if hot-unplug feature
> hasn't been negotiated.
>
> Signed-off-by: Igor Mammedov <imamm...@redhat.com>
> ---
> hw/acpi/ich9.c | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> diff --git a/hw/acpi/ich9.c b/hw/acpi/ich9.c
> index 0acc9a3107..98fc363186 100644
> --- a/hw/acpi/ich9.c
> +++ b/hw/acpi/ich9.c
> @@ -460,6 +460,17 @@ void ich9_pm_device_unplug_request_cb(HotplugHandler
> *hotplug_dev,
> errp);
> } else if (object_dynamic_cast(OBJECT(dev), TYPE_CPU) &&
> !lpc->pm.cpu_hotplug_legacy) {
> + uint64_t negotiated = lpc->smi_negotiated_features;
> +
> + if (negotiated & BIT_ULL(ICH9_LPC_SMI_F_BROADCAST_BIT) &&
> + !(negotiated & BIT_ULL(ICH9_LPC_SMI_F_CPU_HOT_UNPLUG_BIT))) {
> + error_setg(errp, "cpu hot-unplug with SMI wasn't enabled "
> + "by firmware");
> + error_append_hint(errp, "update machine type to newer than 5.1 "
> + "and firmware that suppors CPU hot-unplug with SMM");
(2) I think the "machine type to newer than 5.1" reference should be removed at
this point. (Similarly to how "x-smi-cpu-hotunplug" should default to "false"
at this point in time, in patch#1.) We don't know when hot-unplug will work; we
only know that it doesn't work now.
We could say something like
error_append_hint(errp, "update machine type to a version having "
"x-smi-cpu-hotunplug=on and firmware that "
"suppors CPU hot-unplug with SMM");
> + return;
> + }
> +
> acpi_cpu_unplug_request_cb(hotplug_dev, &lpc->pm.cpuhp_state,
> dev, errp);
> } else {
>
These superficial comments aside, the patch works for me:
Tested-by: Laszlo Ersek <ler...@redhat.com>
and with (1) and (2) fixed:
Reviewed-by: Laszlo Ersek <ler...@redhat.com>
Thanks
Laszlo
