On Fri, Nov 27, 2009 at 02:05:46PM +0530, M. Mohan Kumar wrote: > On 11/27/2009 12:56 AM, Bernhard Walle wrote: > >M. Mohan Kumar schrieb: > >>On 11/26/2009 12:22 AM, Bernhard Walle wrote: > >>>M. Mohan Kumar schrieb: > >>>>Reserve memory for kdump kernel within RMO region > >>>> > >>>>When the kernel size exceeds 32MB(observed with some distros), memory > >>>>for kdump kernel can not be reserved as kdump kernel base is assumed to > >>>>be 32MB always. When the kernel has CONFIG_RELOCATABLE option enabled, > >>>>provide the feature to reserve the memory for kdump kernel anywhere in > >>>>the RMO region. > >> > >>Hi Bernhard, > >> > >>>Correct me if I'm wrong, but: CONFIG_RELOCATABLE is for the kernel that > >>>gets loaded as crashkernel, not for the kernel that loads the > >>>crashkernel. So it would be perfectly fine that a kernel that has not > >>>CONFIG_RELOCATABLE set would load another kernel that has > >>>CONFIG_RELOCATABLE set on an address != 32 M. > >> > >>No, with relocatable option, the same kernel is used as both production > >>and kdump kernel. > > > >Can be, but it's not strictly necessary. It depends what userland does. > >Especially it's possible that a non-relocatable, self-compiled kernel > >loads a relocatable distribution kernel as capture kernel. > > > > I don't understand why a non-relocatable kernel will use relocatable > kernel for capturing kdump kernel. The idea for relocatable kernel > is to avoid using two different kernels to capture kernel dump. True, but that doesn't necessarily mean that using a relocatable kdump kernel is required. Well, hopefully not. > >Also, it would make sense to make the behaviour symmetric across > >platforms. Currently we have: > > > > - x86 and ia64: Without offset on command line, use any offset > > With offset on command line, use that offset and fail > > if no memory is available at that offset. > > - ppc64: Always use 32M and ignore the offset. > > > >If your patch gets applied, we have: > > > > - ppc64: With CONFIG_RELOCATABLE, use any offset > > With offset on command > > > >I don't see why the behaviour on ppc64 should be completely different. > > > >Having maintained kdump for SUSE for x86, ia64 and partly ppc64 in the > >past, I always felt that ppc64 is more different from x86 than ia64 is > >from x86. That's one more step into that direction without a technical > >reason. > > Also with the crashkernel=auto parameter (patches are not yet > merged), the crashkernel base (offset) by default would be 32MB. In > this case if a kernel passed with crashkernel=auto and if the first > kernel size exceeds 32MB, memory for kdump kernel will always fail. > > > > >Having that all said: If your patch gets in mainline kernel, than we > >should change the behaviour also for x86 and ia64. > > > > > > > >Regards, > >Bernhard > > > _______________________________________________ > kexec mailing list > kexec at lists.infradead.org > http://lists.infradead.org/mailman/listinfo/kexec
