Konrad Rzeszutek Wilk wrote: > On Thu, Dec 06, 2012 at 04:27:36AM +0000, Liu, Jinsong wrote: >>>>>> diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig index >>>>>> 126d8ce..abd0396 100644 --- a/drivers/xen/Kconfig >>>>>> +++ b/drivers/xen/Kconfig >>>>>> @@ -206,4 +206,15 @@ config XEN_MCE_LOG >>>>>> Allow kernel fetching MCE error from Xen platform and >>>>>> converting it into Linux mcelog format for mcelog tools >>>>>> >>>>>> +config XEN_ACPI_MEMORY_HOTPLUG >>>>>> + bool "Xen ACPI memory hotplug" >>>>> >>>>> There should be a way to make this a module. >>>> >>>> I have some concerns to make it a module: >>>> 1. xen and native memhotplug driver both work as module, while we >>>> need early load xen driver. >>>> 2. if possible, a xen stub driver may solve load sequence issue, >>>> but it may involve other issues * if xen driver load then unload, >>>> native driver may have chance to load successfully; >>> >>> The stub driver would still "occupy" the ACPI bus for the memory >>> hotplug PnP, so I think this would not be a problem. >>> >> >> I'm not quite clear your mean here, do you mean it has >> 1. xen_stub driver + xen_memhoplug driver, then xen_strub driver >> unload and entirely replaced by xen_memhotplug driver, or >> 2. xen_stub driver (w/ stub ops) + xen_memhotplug ops (not driver), >> then xen_stub driver keep occupying but its stub ops later replaced >> by xen_memhotplug ops? > > #2 >> >> If in way #1, it has risk that native driver may load (if xen driver >> unload). >> If in way #2, xen_memhotplug ops lose the chance to probe/add/bind >> existed memory devices (since it's done when driver registerred). > > Could the stub driver have a queue of events?
If so, why not do 'real' add ops (like our patch did, to build-in xen memory hotplug logic)? I'm not quite clear your purpose of insisting module -- what's advantage of module you prefer? > >> >>>> * if xen driver load --> unload --> load again, then it will lose >>>> hotplug notification during unload period; >>> >>> Sure. But I think we can do it with this driver? After all the >>> function of it is to just tell the firmware to turn on/off sockets >>> - and if we miss one notification we won't take advantage of the >>> power savings - but we can do that later on. >>> >> >> Not only inform firmware. >> Hotplug notify callback will invoke acpi_bus_add -> ... -> >> implicitly invoke drv->ops.add method to add the hotadded memory >> device. > > Gotcha. ? So it will lose the notification and no way to add the new memory device in the future. Xen memory hotplug logic consist of 2 parts: 1) driver logic (.add/.remove etc) 2) notification install/callback logic If you want to use 'xen_stub driver + .add/.remove ops', then notification install/callback logic would implement with xen_stub driver (means in build-in part, otherwise it would lose notification when the ops unload) --> but that would make xen_stub in big build-in size. >> >>> >>>> * if xen driver load --> unload --> load again, then it will >>>> re-add all memory devices, but the handle for 'booting memory >>>> device' and 'hotplug memory device' are different while we have no >>>> way to distinguish these 2 kind of devices. >>> >>> Wouldn't the stub driver hold onto that? >>> >> >> Same question as comment #1. Do you mean it has a xen_stub driver >> (w/ stub ops) and a xen_memhotplug ops? > > Correct. >> >>>> >>>> IMHO I think to make xen hotplug logic as module may involves >>>> unexpected result. Is there any obvious advantages of doing so? >>>> after all we have provided config choice to user. Thoughts? >>> >>> Yes, it becomes a module - which is what we want. >>> >> >> What I meant here is, module will bring some unexpected issues for >> xen hotplug. >> We can provide user 'bool' config choice, let them decide to >> build-in or not, but not 'tristate' choice. > > What would be involved in making it an tristate choice? >> >> Thanks >> Jinsong -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
