On Thursday, January 09, 2014 04:44:25 PM Vivek Goyal wrote: > On Thu, Jan 09, 2014 at 04:34:16PM -0500, KOSAKI Motohiro wrote: > > On Thu, Jan 9, 2014 at 10:00 AM, Vivek Goyal <vgoyal at redhat.com> wrote: > > > On Thu, Jan 09, 2014 at 12:00:29AM +0100, Rafael J. Wysocki wrote: > > > > > > [..] > > >> > The system then panics and the kdump/kexec kernel boots. During this boot > > >> > ACPi is initialized and the kernel (as can be seen above) > > >> > > >> Which is a bug. You're not supposed to initialize ACPI twice in a row. > > > > > > [CC lkml, kexec mailing list, dave young] > > > > > > It is a fresh instance of kernel booting and it is initializing its data > > > structures fresh. It is *not* re-initializing ACPI in same kernel. > > > > > >> > This patchset resolves the problem by adding a kernel parameter, > > >> > no_memory_hotplug, to disable ACPI memory hotplug. It can be added by default > > >> > as a parameter to the kexec/kdump kernel so the kernel boots correctly. > > >> > > >> This problem is specific to kexec/kdump, so please don't add *generic* command > > >> line parameters to address this. > > >> > > > > > > There are other command line options to solve kdump problems. In general > > > one might want to disable memory hogplug on the fly even if it is compiled > > > in the kernel. So it can act as a good debugging aid. > > > > > > Secondly, it can be specified with memmap=exactmap and mem=X paramters to > > > make sure no memory is hot added in the system. > > > > > > So I can see other usages of this parameter. To me it makes sense to have > > > a separate command line option to disable memory hotplug feature on the > > > fly. > > > > I'm ok this option. But note, even if this option is specified, SH, > > Power and S390 still > > be able to use memory hotplug because their firmware are totally > > different from ACPI. > > > > Maybe, adding acpi prefix provides good clarification. > > Makes sense. Something like "acpi_no_memhotplug" or "acpi_disable_memhotplug" > or something else. acpi_no_memhotplug would make more sense. That said if you make memmap=exactmap disable the memhotplug driver, the existing kexec/kdump users won't need to be updated. Thanks, Rafael
