On Thu, Nov 12, 2015 at 09:54:18AM +0100, Ingo Molnar wrote: > > * Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> 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 > > @@ -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). -- Kirill A. Shutemov -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>