On Fri, Mar 17, 2017 at 11:22 AM, John Hubbard <jhubbard@xxxxxxxxxx> wrote: > On 03/16/2017 04:05 PM, Andrew Morton wrote: >> >> On Thu, 16 Mar 2017 12:05:26 -0400 Jérôme Glisse <jglisse@xxxxxxxxxx> >> wrote: >> >>> +static inline struct page *migrate_pfn_to_page(unsigned long mpfn) >>> +{ >>> + if (!(mpfn & MIGRATE_PFN_VALID)) >>> + return NULL; >>> + return pfn_to_page(mpfn & MIGRATE_PFN_MASK); >>> +} >> >> >> i386 allnoconfig: >> >> In file included from mm/page_alloc.c:61: >> ./include/linux/migrate.h: In function 'migrate_pfn_to_page': >> ./include/linux/migrate.h:139: warning: left shift count >= width of type >> ./include/linux/migrate.h:141: warning: left shift count >= width of type >> ./include/linux/migrate.h: In function 'migrate_pfn_size': >> ./include/linux/migrate.h:146: warning: left shift count >= width of type >> > > It seems clear that this was never meant to work with < 64-bit pfns: > > // migrate.h excerpt: > #define MIGRATE_PFN_VALID (1UL << (BITS_PER_LONG_LONG - 1)) > #define MIGRATE_PFN_MIGRATE (1UL << (BITS_PER_LONG_LONG - 2)) > #define MIGRATE_PFN_HUGE (1UL << (BITS_PER_LONG_LONG - 3)) > #define MIGRATE_PFN_LOCKED (1UL << (BITS_PER_LONG_LONG - 4)) > #define MIGRATE_PFN_WRITE (1UL << (BITS_PER_LONG_LONG - 5)) > #define MIGRATE_PFN_DEVICE (1UL << (BITS_PER_LONG_LONG - 6)) > #define MIGRATE_PFN_ERROR (1UL << (BITS_PER_LONG_LONG - 7)) > #define MIGRATE_PFN_MASK ((1UL << (BITS_PER_LONG_LONG - PAGE_SHIFT)) > - 1) > > ...obviously, there is not enough room for these flags, in a 32-bit pfn. > > So, given the current HMM design, I think we are going to have to provide a > 32-bit version of these routines (migrate_pfn_to_page, and related) that is > a no-op, right? Or make the HMM Kconfig feature 64BIT only by making it depend on 64BIT? Balbir Singh -- 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