diff options
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 7 | ||||
| -rw-r--r-- | arch/x86/kernel/setup.c | 22 |
2 files changed, 19 insertions, 10 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 2b8ee90bb644..24d01648edeb 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -704,8 +704,11 @@ upon panic. This parameter reserves the physical memory region [offset, offset + size] for that kernel image. If '@offset' is omitted, then a suitable offset - is selected automatically. Check - Documentation/kdump/kdump.txt for further details. + is selected automatically. + [KNL, x86_64] select a region under 4G first, and + fall back to reserve region above 4G when '@offset' + hasn't been specified. + See Documentation/kdump/kdump.txt for further details. crashkernel=range1:size1[,range2:size2,...][@offset] [KNL] Same as above, but depends on the memory diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c index daf7c5650c18..c15f362a2516 100644 --- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -541,21 +541,27 @@ static void __init reserve_crashkernel(void) } /* 0 means: find the address automatically */ - if (crash_base <= 0) { + if (!crash_base) { /* * Set CRASH_ADDR_LOW_MAX upper bound for crash memory, - * as old kexec-tools loads bzImage below that, unless - * "crashkernel=size[KMG],high" is specified. + * crashkernel=x,high reserves memory over 4G, also allocates + * 256M extra low memory for DMA buffers and swiotlb. + * But the extra memory is not required for all machines. + * So try low memory first and fall back to high memory + * unless "crashkernel=size[KMG],high" is specified. */ - crash_base = memblock_find_in_range(CRASH_ALIGN, - high ? CRASH_ADDR_HIGH_MAX - : CRASH_ADDR_LOW_MAX, - crash_size, CRASH_ALIGN); + if (!high) + crash_base = memblock_find_in_range(CRASH_ALIGN, + CRASH_ADDR_LOW_MAX, + crash_size, CRASH_ALIGN); + if (!crash_base) + crash_base = memblock_find_in_range(CRASH_ALIGN, + CRASH_ADDR_HIGH_MAX, + crash_size, CRASH_ALIGN); if (!crash_base) { pr_info("crashkernel reservation failed - No suitable area found.\n"); return; } - } else { unsigned long long start; |