Hi Takahiro,
On Thursday 26 March 2015 01:58 PM, AKASHI Takahiro wrote:
Crash dump kernel will access memory regions in system kernel via copy_oldmem_page(), which reads a page with ioremap'ing it assuming that such pages are not part of main memory of crash dump kernel. This is true under non-UEFI environment because kexec-tools modifies a device tree adding "usablemem" attributes to memory sections. Under UEFI, however, this is not true because UEFI remove memory sections in a device tree and export all the memory regions, even though they belong to system kernel.
So we should add "mem=X[MG]" boot parameter to limit the meory size and avoid hitting the following assertion in ioremap(): if (WARN_ON(pfn_valid(__phys_to_pfn(phys_addr)))) return NULL;
Well I am using your updated kexec-tool which has support of automatic addition of "mem=" parameter. I found that this warning is still appearing and therefore another error about "Kdump: vmcore not initialized".
Memory address for which ioremap failed was almost at the top of crash_reserved_mem. So I modified kexec-tool [1] to accept user specific mem= parameter with a value lesser than physical location which was being remapped, however still the warning was there.
Further I noticed that there is no reserved memblock with nonzero memblock_region->size when early_mem -> memblock_enforce_memory_limit is called. Therefore this mem= param is not limiting memory location in my case.
I was just wondering, why do not we use ioremap_cache instead of ioremap in copy_oldmem_page?
~Pratyush
[1] https://github.com/pratyushanand/kexec-tools/commit/7dc38d587cb32d4522f6baf0...