Commit 09c71bfd authored Mar 28, 2012 by Dave Young Committed by Linus Torvalds Mar 28, 2012

kdump x86: fix total mem size calculation for reservation



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.

Signed-off-by: Dave Young <dyoung@redhat.com>
Reviewed-by: WANG Cong <xiyou.wangcong@gmail.com>
Reviewed-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent eaa3be6a

arch/x86/kernel/setup.c

+1 −10

Original line number	Diff line number	Diff line
		@@ -509,15 +509,6 @@ static void __init memblock_x86_reserve_range_setup_data(void)

		#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(void)
		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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