Messages in this thread Patch in this message | | | Date | Sat, 10 Mar 2012 12:56:33 +0800 | From | Dave Young <> | Subject | [PATCH v2] kdump x86: fix total mem size calculation for reservation |
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crashkernel reservation need know the total memory size. Current get_total_mem simply use max_pfn - min_low_pfn. It is wrong because it will including memory holes in the middle.
Especially for kvm guest with memory > 0xe0000000, there's below in qemu code: qemu split memory as below: if (ram_size >= 0xe0000000 ) { above_4g_mem_size = ram_size - 0xe0000000; below_4g_mem_size = 0xe0000000; } else { below_4g_mem_size = ram_size; } So for 4G mem guest, seabios will insert a 512M usable region beyond of 4G. Thus in above case max_pfn - min_low_pfn will be more than original memsize.
Fixing this issue by using memblock_phys_mem_size() to get the total memsize.
[v1 -> v2]: refresh the patch based on latest linus tree
Signed-off-by: Dave Young <dyoung@redhat.com> --- [Ther's similar code in arm, I'm not sure whether the memblock_phys_mem_size works with arm or not. If it works I can also update that part of code.] arch/x86/kernel/setup.c | 11 +---------- 1 file changed, 1 insertion(+), 10 deletions(-)
--- linux-2.6.orig/arch/x86/kernel/setup.c 2012-03-04 03:46:35.000000000 +0800 +++ linux-2.6/arch/x86/kernel/setup.c 2012-03-10 12:44:58.133300788 +0800 @@ -509,15 +509,6 @@ static void __init memblock_x86_reserve_ #ifdef CONFIG_KEXEC -static inline unsigned long long get_total_mem(void) -{ - unsigned long long total; - - total = max_pfn - min_low_pfn; - - return total << PAGE_SHIFT; -} - /* * Keep the crash kernel below this limit. On 32 bits earlier kernels * would limit the kernel to the low 512 MiB due to mapping restrictions. @@ -536,7 +527,7 @@ static void __init reserve_crashkernel(v unsigned long long crash_size, crash_base; int ret; - total_mem = get_total_mem(); + total_mem = memblock_phys_mem_size(); ret = parse_crashkernel(boot_command_line, total_mem, &crash_size, &crash_base);
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