On 06/06/2013 10:55:22 PM, Aneesh Kumar K.V wrote:
> Scott Wood <scottwood@freescale.com> writes:
> 
> > On 04/28/2013 02:37:30 PM, Aneesh Kumar K.V wrote:
> >> From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
> >>
> >> We will be switching PMD_SHIFT to 24 bits to facilitate THP
> >> impmenetation.
> >> With PMD_SHIFT set to 24, we now have 16MB huge pages allocated at
> >> PGD level.
> >> That means with 32 bit process we cannot allocate normal pages at
> >> all, because we cover the entire address space with one pgd entry.
> >> Fix this
> >> by switching to a new page table format for hugepages. With the new
> >> page table
> >> format for 16GB and 16MB hugepages we won't allocate hugepage
> >> directory. Instead
> >> we encode the PTE information directly at the directory level. This
> >> forces 16MB
> >> hugepage at PMD level. This will also make the page take walk much
> >> simpler later
> >> when we add the THP support.
> >>
> >> With the new table format we have 4 cases for pgds and pmds:
> >> (1) invalid (all zeroes)
> >> (2) pointer to next table, as normal; bottom 6 bits == 0
> >> (3) leaf pte for huge page, bottom two bits != 00
> >> (4) hugepd pointer, bottom two bits == 00, next 4 bits indicate  
> size
> >> of table
> >>
> >> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
> >> ---
> >>  arch/powerpc/include/asm/page.h    |   2 +
> >>  arch/powerpc/include/asm/pgtable.h |   2 +
> >>  arch/powerpc/mm/gup.c              |  18 +++-
> >>  arch/powerpc/mm/hugetlbpage.c      | 176
> >> +++++++++++++++++++++++++++++++------
> >>  4 files changed, 168 insertions(+), 30 deletions(-)
> >
> > After this patch, on 64-bit book3e (e5500, and thus 4K pages), I see
> > messages like this after exiting a program that uses hugepages
> > (specifically, qemu):
> >
> > /home/scott/fsl/git/linux/upstream/mm/memory.c:407: bad pmd
> > 40000001fc221516.
> > /home/scott/fsl/git/linux/upstream/mm/memory.c:407: bad pmd
> > 40000001fc221516.
> > /home/scott/fsl/git/linux/upstream/mm/memory.c:407: bad pmd
> > 40000001fc2214d6.
> > /home/scott/fsl/git/linux/upstream/mm/memory.c:407: bad pmd
> > 40000001fc2214d6.
> > /home/scott/fsl/git/linux/upstream/mm/memory.c:407: bad pmd
> > 40000001fc221916.
> > /home/scott/fsl/git/linux/upstream/mm/memory.c:407: bad pmd
> > 40000001fc221916.
> > /home/scott/fsl/git/linux/upstream/mm/memory.c:407: bad pmd
> > 40000001fc2218d6.
> > /home/scott/fsl/git/linux/upstream/mm/memory.c:407: bad pmd
> > 40000001fc2218d6.
> > /home/scott/fsl/git/linux/upstream/mm/memory.c:407: bad pmd
> > 40000001fc221496.
> > /home/scott/fsl/git/linux/upstream/mm/memory.c:407: bad pmd
> > 40000001fc221496.
> > /home/scott/fsl/git/linux/upstream/mm/memory.c:407: bad pmd
> > 40000001fc221856.
> > /home/scott/fsl/git/linux/upstream/mm/memory.c:407: bad pmd
> > 40000001fc221856.
> > /home/scott/fsl/git/linux/upstream/mm/memory.c:407: bad pmd
> > 40000001fc221816.
> 
> hmm that implies some of the code paths are not properly #ifdef.
> The goal was to limit the new format CONFIG_PPC_BOOK3S_64 as seen in  
> the
> definition of huge_pte_alloc. Can you send me the .config ?

Attached.

-Scott