Messages in this thread | | | Subject | Re: [HMM 07/16] mm/migrate: new memory migration helper for use with device memory v4 | From | John Hubbard <> | Date | Thu, 16 Mar 2017 17:22:51 -0700 |
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On 03/16/2017 04:05 PM, Andrew Morton wrote: > On Thu, 16 Mar 2017 12:05:26 -0400 Jérôme Glisse <jglisse@redhat.com> 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?
thanks John Hubbard NVIDIA
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