Messages in this thread | | | Date | Mon, 11 Feb 2008 14:08:43 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH] [6/8] Account overlapped mappings in end_pfn_map |
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* Andi Kleen <ak@suse.de> 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 address.
> 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".
Ingo
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