The patch titled Subject: x86: mm: add missing comments for initial kernel direct mapping has been added to the -mm tree. Its filename is x86-mm-add-missing-comments-for-initial-kernel-direct-mapping.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Zhang Yanfei <zhangyanfei@xxxxxxxxxxxxxx> Subject: x86: mm: add missing comments for initial kernel direct mapping For some reason, comments below are lost: - comments for init_range_memory_mapping() - comments in init_mem_mapping that is helpful for reminding people that the pagetable is setup top-down The comments were written by Yinghai in his patch in https://lkml.org/lkml/2012/11/28/620 Signed-off-by: Zhang Yanfei <zhangyanfei@xxxxxxxxxxxxxx> Signed-off-by: Yinghai Lu <yinghai@xxxxxxxxxx> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> Cc: Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- arch/x86/mm/init.c | 19 ++++++++++++++++++- 1 file changed, 18 insertions(+), 1 deletion(-) diff -puN arch/x86/mm/init.c~x86-mm-add-missing-comments-for-initial-kernel-direct-mapping arch/x86/mm/init.c --- a/arch/x86/mm/init.c~x86-mm-add-missing-comments-for-initial-kernel-direct-mapping +++ a/arch/x86/mm/init.c @@ -359,7 +359,17 @@ unsigned long __init_refok init_memory_m } /* - * would have hole in the middle or ends, and only ram parts will be mapped. + * We need to iterate through E820 memory map and create direct mappings + * for only E820_RAM and E820_KERN_RESERVED regions. We cannot simply + * create direct mappings for all pfns from [0 to max_low_pfn) and + * [4GB to max_pfn) because of possible memory holes in high addresses + * that cannot be marked as UC by fixed/variable range MTRRs. + * Depending on the alignment of E820 ranges, this may possibly result + * in using smaller size (i.e. 4K instead of 2M or 1G) page tables. + * + * init_mem_mapping call init_range_memory_mapping with big range. + * That range would have hole in the middle or ends, and only ram parts + * will be mapped in init_range_memory_mapping. */ static unsigned long __init init_range_memory_mapping( unsigned long r_start, @@ -419,6 +429,13 @@ void __init init_mem_mapping(void) max_pfn_mapped = 0; /* will get exact value next */ min_pfn_mapped = real_end >> PAGE_SHIFT; last_start = start = real_end; + + /* + * We start from the top (end of memory) and go to the bottom. + * The memblock_find_in_range gets us a block of RAM from the + * end of RAM in [min_pfn_mapped, max_pfn_mapped) as new pages + * for page table. + */ while (last_start > ISA_END_ADDRESS) { if (last_start > step_size) { start = round_down(last_start - 1, step_size); _ Patches currently in -mm which might be from zhangyanfei@xxxxxxxxxxxxxx are origin.patch x86-mm-add-missing-comments-for-initial-kernel-direct-mapping.patch ipvs-change-type-of-netns_ipvs-sysctl_sync_qlen_max.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html