On 12/13/2012 10:42 PM, Toshi Kani wrote: > On Tue, 2012-12-11 at 22:34 +0800, Jiang Liu wrote: >> On 12/08/2012 09:08 AM, Toshi Kani wrote: >>> On Fri, 2012-12-07 at 13:57 +0800, Jiang Liu wrote: >>>> On 2012-12-7 10:57, Toshi Kani wrote: >>>>> On Fri, 2012-12-07 at 00:40 +0800, Jiang Liu wrote: >>>>>> On 12/04/2012 08:10 AM, Toshi Kani wrote: >>>>>>> On Mon, 2012-12-03 at 12:25 +0800, Hanjun Guo wrote: >>>>>>>> On 2012/11/30 6:27, Toshi Kani wrote: >>>>>>>>> On Thu, 2012-11-29 at 12:48 +0800, Hanjun Guo wrote: > : >>>>> Yes, the framework should allow such future work. I also think that the >>>>> framework itself should be independent from such ACPI issue. Ideally, >>>>> it should be able to support non-ACPI platforms. >>>> The same point here. The ACPI based hotplug framework is designed as: >>>> 1) an ACPI based hotplug slot driver to handle platform specific logic. >>>> Platform may provide platform specific slot drivers to discover, manage >>>> hotplug slots. We have provided a default implementation of slot driver >>>> according to the ACPI spec. >>> >>> The ACPI spec does not define that _EJ0 is required to receive a hot-add >>> request, i.e. bus/device check. This is a major issue. Since Windows >>> only supports hot-add, I think there are platforms that only support >>> hot-add today. >>> >>>> 2) an ACPI based hotplug manager driver, which is a platform independent >>>> driver and manages all hotplug slot created by the slot driver. >>> >>> It is surely impressive work, but I think is is a bit overdoing. I >>> expect hot-pluggable servers come with management console and/or GUI >>> where a user can manage hardware units and initiate hot-plug operations. >>> I do not think the kernel needs to step into such area since it tends to >>> be platform-specific. >> One of the major usages of this feature is for testing. >> It will be hard for OSVs and OEMs to verify hotplug functionalities if it could >> only be tested by physical hotplug or through management console. So to pave the >> way for hotplug, we need to provide a mechanism for OEMs and OSVs to execute >> auto stress tests for hotplug functionalities. > > Yes, but such OS->FW interface is platform-specific. Some platforms use > IPMI for the OS to communicate with the management console. In this > case, an OEM-specific command can be used to request a hotplug through > IPMI. Some platforms may also support test programs to run on the > management console for validations. > > For early development testing, Yinghai's SCI emulation patch can be used > to emulate hotplug events from the OS. It would be part of the kernel > debugging features once this patch is accepted. Hi Toshi, ACPI 5.0 has provided some mechanism to normalize the way to issue RAS related requests to firmware. I hope ACPI 5.x will define some standardized ways based on the PCC defined in 5.0. If needed, we may provide platform specific methods for them too. Regards! Gerry > > >>>> We haven't gone further enough to provide an ACPI independent hotplug framework >>>> because we only have experience with x86 and Itanium, both are ACPI based. >>>> We may try to implement an ACPI independent hotplug framework by pushing all >>>> ACPI specific logic into the slot driver, I think it's doable. But we need >>>> suggestions from experts of other architectures, such as SPARC and Power. >>>> But seems Power already have some sorts of hotplug framework, right? >>> >>> I do not know about the Linux hot-plug support on other architectures. >>> PA-RISC SuperDome also supports Node hot-plug, but it is not supported >>> by Linux. Since ARM is getting used by servers, I would not surprise if >>> there will be an ARM based server with hot-plug support in future. >> Seems ARM is on the way to adopt ACPI, so may be we could support ARM servers >> in the future. > > That's good to know. > > : >>>>>> So in our framework, we have an option to relay hotplug event from firmware >>>>>> to userspace, so the userspace has a chance to reject the hotplug operations >>>>>> if it may cause unacceptable disturbance to userspace services. >>>>> >>>>> I think validation from user-space is necessary for deleting I/O >>>>> devices. For CPU and memory, the kernel check works fine. >>>> Agreed. But we may need help from userspace to handle cgroup/cpuset/cpuisol >>>> etc for cpu and memory hot-removal. Especially for telecom applications, they >>>> have strong dependency on cgroup/cpuisol to guarantee latency. >>> >>> I have not looked at the code, but isn't these cpu attributes managed in >>> the kernel? >> Some Telecom applications want to run in an deterministic environment, so they >> depend on cpuisol/cpuset to provide such an environment. If hotplug event happens, >> these Telecom application should be notified so they have a chance to redistribute >> the workload. > > I agree that we need to generate an event that can be subscribed by > those applications, so that they can react quickly on the change. > > Thanks, > -Toshi > > -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
