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. > 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
