Messages in this thread | | | Subject | Re: [PATCH] x86/mm: fix regression with huge pages on PAE | From | Boris Ostrovsky <> | Date | Tue, 24 Nov 2015 09:59:27 -0500 |
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On 11/12/2015 04:00 AM, Kirill A. Shutemov wrote: > On Thu, Nov 12, 2015 at 09:54:18AM +0100, Ingo Molnar wrote: >> * Kirill A. Shutemov <kirill.shutemov@linux.intel.com> wrote: >> >>> diff --git a/arch/x86/include/asm/page_types.h b/arch/x86/include/asm/page_types.h >>> index c5b7fb2774d0..cc071c6f7d4d 100644 >>> --- a/arch/x86/include/asm/page_types.h >>> +++ b/arch/x86/include/asm/page_types.h
Kirill, where are we with this patch?
-boris
>>> @@ -9,19 +9,21 @@ >>> #define PAGE_SIZE (_AC(1,UL) << PAGE_SHIFT) >>> #define PAGE_MASK (~(PAGE_SIZE-1)) >>> >>> +#define PMD_PAGE_SIZE (_AC(1, UL) << PMD_SHIFT) >>> +#define PMD_PAGE_MASK (~(PMD_PAGE_SIZE-1)) >>> + >>> +#define PUD_PAGE_SIZE (_AC(1, UL) << PUD_SHIFT) >>> +#define PUD_PAGE_MASK (~(PUD_PAGE_SIZE-1)) >>> + >>> #define __PHYSICAL_MASK ((phys_addr_t)((1ULL << __PHYSICAL_MASK_SHIFT) - 1)) >>> #define __VIRTUAL_MASK ((1UL << __VIRTUAL_MASK_SHIFT) - 1) >>> >>> -/* Cast PAGE_MASK to a signed type so that it is sign-extended if >>> +/* Cast *PAGE_MASK to a signed type so that it is sign-extended if >>> virtual addresses are 32-bits but physical addresses are larger >>> (ie, 32-bit PAE). */ >>> #define PHYSICAL_PAGE_MASK (((signed long)PAGE_MASK) & __PHYSICAL_MASK) >>> - >>> -#define PMD_PAGE_SIZE (_AC(1, UL) << PMD_SHIFT) >>> -#define PMD_PAGE_MASK (~(PMD_PAGE_SIZE-1)) >>> - >>> -#define PUD_PAGE_SIZE (_AC(1, UL) << PUD_SHIFT) >>> -#define PUD_PAGE_MASK (~(PUD_PAGE_SIZE-1)) >>> +#define PHYSICAL_PMD_PAGE_MASK (((signed long)PMD_PAGE_MASK) & __PHYSICAL_MASK) >>> +#define PHYSICAL_PUD_PAGE_MASK (((signed long)PUD_PAGE_MASK) & __PHYSICAL_MASK) >> that's a really odd way of writing it, 'long' is signed by default ... > See the comment above (it was there before the patch). 'signed' can be > considered as documentation -- we want sign-extension here. > >> There seems to be 150+ such cases in the kernel source though - weird. >> >> More importantly, how does this improve things on 32-bit PAE kernels? If I follow >> the values correctly then PMD_PAGE_MASK is 'UL' i.e. 32-bit: >> >>> +#define PMD_PAGE_SIZE (_AC(1, UL) << PMD_SHIFT) >>> +#define PMD_PAGE_MASK (~(PMD_PAGE_SIZE-1)) >> thus PHYSICAL_PMD_PAGE_MASK is 32-bit too: >> >>> +#define PHYSICAL_PMD_PAGE_MASK (((signed long)PMD_PAGE_MASK) & __PHYSICAL_MASK) >> so how is the bug fixed? > Again, see the comment. > I've checked that it generates correct value (using kernel/bounds.c). >
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