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    SubjectRe: [PATCH] [6/8] Account overlapped mappings in end_pfn_map

    * Andi Kleen <> wrote:

    > When end_pfn is not aligned to 2MB (or 1GB) then the kernel might map
    > more memory than end_pfn. Account this in end_pfn_mapped.

    can you see any practical relevance? Your patch description only deals
    with the mechanical details of the change instead of analyzing the most
    important thing: relevance and impact analysis. That makes it harder to
    add your patches and easier to miss a good fix accidentally. It also
    makes it quite a bit harder to trust your patches.

    at a quick glance the relevance is to EFI only, in
    efi_enter_virtual_mode(). max_pfn_mapped is used as a differentiator
    between __va() and efi_ioremap(). AFAICS EFI will typically have its
    runtime code not right after the end of physical memory.

    Nevertheless, i do agree that the max_pfn_mapped/end_pfn_map limit needs
    to be sharpened to reflect reality (for later PAT support).

    your patch is also a bit unclean:

    > -static void __meminit
    > +static unsigned long __meminit
    > phys_pmd_update(pud_t *pud, unsigned long address, unsigned long end)
    > {
    > + unsigned long r;
    > pmd_t *pmd = pmd_offset(pud, 0);
    > spin_lock(&init_mm.page_table_lock);
    > - phys_pmd_init(pmd, address, end);
    > + r = phys_pmd_init(pmd, address, end);
    > spin_unlock(&init_mm.page_table_lock);
    > __flush_tlb_all();
    > + return r;
    > }

    a meaningless "r" parameter. Use "true_end" instead.

    and here's another type of variable naming problem:

    > +unsigned long __init_refok
    > +init_memory_mapping(unsigned long start, unsigned long end)
    > {
    > - unsigned long next;
    > + unsigned long next, true_end = end;

    that "true_end" is already a _pfn_, so name it accordingly:
    true_end_pfn. Because we switch between pfn and addr types it's
    important to point out where it's pfn and where it's a linear/physical

    > struct zone *zone = pgdat->node_zones + ZONE_NORMAL;
    > unsigned long start_pfn = start >> PAGE_SHIFT;
    > unsigned long nr_pages = size >> PAGE_SHIFT;
    > + unsigned long r;
    > int ret;
    > - init_memory_mapping(start, start + size-1);
    > + r = init_memory_mapping(start, start + size-1);
    > + if (r > end_pfn_map)
    > + end_pfn_map = r;

    rename "r" to "true_end_pfn".


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