On Fri, Jan 27, 2017 at 12:06:02PM +0100, Vlastimil Babka wrote: > On 12/27/2016 02:53 AM, Kirill A. Shutemov wrote: > >We are going to switch core MM to 5-level paging abstraction. > > > >This is preparation step which adds <asm-generic/5level-fixup.h> > >As with 4level-fixup.h, the new header allows quickly make all > >architectures compatible with 5-level paging in core MM. > > > >In long run we would like to switch architectures to properly folded p4d > >level by using <asm-generic/pgtable-nop4d.h>, but it requires more > >changes to arch-specific code. > > > >Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> > >--- > > include/asm-generic/4level-fixup.h | 3 ++- > > include/asm-generic/5level-fixup.h | 41 ++++++++++++++++++++++++++++++++++++++ > > include/linux/mm.h | 3 +++ > > 3 files changed, 46 insertions(+), 1 deletion(-) > > create mode 100644 include/asm-generic/5level-fixup.h > > > >diff --git a/include/asm-generic/4level-fixup.h b/include/asm-generic/4level-fixup.h > >index 5bdab6bffd23..928fd66b1271 100644 > >--- a/include/asm-generic/4level-fixup.h > >+++ b/include/asm-generic/4level-fixup.h > >@@ -15,7 +15,6 @@ > > ((unlikely(pgd_none(*(pud))) && __pmd_alloc(mm, pud, address))? \ > > NULL: pmd_offset(pud, address)) > > > >-#define pud_alloc(mm, pgd, address) (pgd) > > This... > > > #define pud_offset(pgd, start) (pgd) > > #define pud_none(pud) 0 > > #define pud_bad(pud) 0 > >@@ -35,4 +34,6 @@ > > #undef pud_addr_end > > #define pud_addr_end(addr, end) (end) > > > >+#include <asm-generic/5level-fixup.h> > > ... plus this... > > >+ > > #endif > >diff --git a/include/asm-generic/5level-fixup.h b/include/asm-generic/5level-fixup.h > >new file mode 100644 > >index 000000000000..b5ca82dc4175 > >--- /dev/null > >+++ b/include/asm-generic/5level-fixup.h > >@@ -0,0 +1,41 @@ > >+#ifndef _5LEVEL_FIXUP_H > >+#define _5LEVEL_FIXUP_H > >+ > >+#define __ARCH_HAS_5LEVEL_HACK > >+#define __PAGETABLE_P4D_FOLDED > >+ > >+#define P4D_SHIFT PGDIR_SHIFT > >+#define P4D_SIZE PGDIR_SIZE > >+#define P4D_MASK PGDIR_MASK > >+#define PTRS_PER_P4D 1 > >+ > >+#define p4d_t pgd_t > >+ > >+#define pud_alloc(mm, p4d, address) \ > >+ ((unlikely(pgd_none(*(p4d))) && __pud_alloc(mm, p4d, address)) ? \ > >+ NULL : pud_offset(p4d, address)) > > ... and this, makes me wonder if that broke pud_alloc() for architectures > that use the 4level-fixup.h. Don't those need to continue having pud_alloc() > as (pgd)? Okay, that's very hacky, but works: For 4level-fixup.h case we have __PAGETABLE_PUD_FOLDED set, so __pud_alloc() will always succeed (see <linux/mm.h>). And pud_offset() from 4level-fixup.h always returns pgd. I've tested this on alpha with qemu. -- 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>
