Commit 09c71bfd authored by Dave Young's avatar Dave Young Committed by Linus Torvalds
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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

Fixing this issue by using memblock_phys_mem_size() to get the total
Signed-off-by: default avatarDave Young <>
Reviewed-by: default avatarWANG Cong <>
Reviewed-by: default avatarSimon Horman <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent eaa3be6a
......@@ -509,15 +509,6 @@ static void __init memblock_x86_reserve_range_setup_data(void)
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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