aboutsummaryrefslogtreecommitdiff
path: root/include/asm-powerpc/pgalloc-64.h
AgeCommit message (Collapse)Author
2008-02-08CONFIG_HIGHPTE vs. sub-page page tables.Martin Schwidefsky
Background: I've implemented 1K/2K page tables for s390. These sub-page page tables are required to properly support the s390 virtualization instruction with KVM. The SIE instruction requires that the page tables have 256 page table entries (pte) followed by 256 page status table entries (pgste). The pgstes are only required if the process is using the SIE instruction. The pgstes are updated by the hardware and by the hypervisor for a number of reasons, one of them is dirty and reference bit tracking. To avoid wasting memory the standard pte table allocation should return 1K/2K (31/64 bit) and 2K/4K if the process is using SIE. Problem: Page size on s390 is 4K, page table size is 1K or 2K. That means the s390 version for pte_alloc_one cannot return a pointer to a struct page. Trouble is that with the CONFIG_HIGHPTE feature on x86 pte_alloc_one cannot return a pointer to a pte either, since that would require more than 32 bit for the return value of pte_alloc_one (and the pte * would not be accessible since its not kmapped). Solution: The only solution I found to this dilemma is a new typedef: a pgtable_t. For s390 pgtable_t will be a (pte *) - to be introduced with a later patch. For everybody else it will be a (struct page *). The additional problem with the initialization of the ptl lock and the NR_PAGETABLE accounting is solved with a constructor pgtable_page_ctor and a destructor pgtable_page_dtor. The page table allocation and free functions need to call these two whenever a page table page is allocated or freed. pmd_populate will get a pgtable_t instead of a struct page pointer. To get the pgtable_t back from a pmd entry that has been installed with pmd_populate a new function pmd_pgtable is added. It replaces the pmd_page call in free_pte_range and apply_to_pte_range. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: <linux-arch@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05add mm argument to pte/pmd/pud/pgd_freeBenjamin Herrenschmidt
(with Martin Schwidefsky <schwidefsky@de.ibm.com>) The pgd/pud/pmd/pte page table allocation functions get a mm_struct pointer as first argument. The free functions do not get the mm_struct argument. This is 1) asymmetrical and 2) to do mm related page table allocations the mm argument is needed on the free function as well. [kamalesh@linux.vnet.ibm.com: i386 fix] [akpm@linux-foundation.org: coding-syle fixes] Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: <linux-arch@vger.kernel.org> Signed-off-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-01-24[POWERPC] Provide a way to protect 4k subpages when using 64k pagesPaul Mackerras
Using 64k pages on 64-bit PowerPC systems makes life difficult for emulators that are trying to emulate an ISA, such as x86, which use a smaller page size, since the emulator can no longer use the MMU and the normal system calls for controlling page protections. Of course, the emulator can emulate the MMU by checking and possibly remapping the address for each memory access in software, but that is pretty slow. This provides a facility for such programs to control the access permissions on individual 4k sub-pages of 64k pages. The idea is that the emulator supplies an array of protection masks to apply to a specified range of virtual addresses. These masks are applied at the level where hardware PTEs are inserted into the hardware page table based on the Linux PTEs, so the Linux PTEs are not affected. Note that this new mechanism does not allow any access that would otherwise be prohibited; it can only prohibit accesses that would otherwise be allowed. This new facility is only available on 64-bit PowerPC and only when the kernel is configured for 64k pages. The masks are supplied using a new subpage_prot system call, which takes a starting virtual address and length, and a pointer to an array of protection masks in memory. The array has a 32-bit word per 64k page to be protected; each 32-bit word consists of 16 2-bit fields, for which 0 allows any access (that is otherwise allowed), 1 prevents write accesses, and 2 or 3 prevent any access. Implicit in this is that the regions of the address space that are protected are switched to use 4k hardware pages rather than 64k hardware pages (on machines with hardware 64k page support). In fact the whole process is switched to use 4k hardware pages when the subpage_prot system call is used, but this could be improved in future to switch only the affected segments. The subpage protection bits are stored in a 3 level tree akin to the page table tree. The top level of this tree is stored in a structure that is appended to the top level of the page table tree, i.e., the pgd array. Since it will often only be 32-bit addresses (below 4GB) that are protected, the pointers to the first four bottom level pages are also stored in this structure (each bottom level page contains the protection bits for 1GB of address space), so the protection bits for addresses below 4GB can be accessed with one fewer loads than those for higher addresses. Signed-off-by: Paul Mackerras <paulus@samba.org>
2007-06-02[POWERPC] Fix return from pte_alloc_one() in out-of-memory caseAkinobu Mita
pte_alloc_one() is expected to return NULL if out of memory. But it returns virt_to_page(NULL), which is not NULL. This fixes it. Cc: Paul Mackerras <paulus@samba.org> Signed-off-by: Akinobu Mita <mita@fixstars.com> Signed-off-by: Paul Mackerras <paulus@samba.org>
2007-05-09[POWERPC] Don't use SLAB/SLUB for PTE pagesHugh Dickins
The SLUB allocator relies on struct page fields first_page and slab, overwritten by ptl when SPLIT_PTLOCK: so the SLUB allocator cannot then be used for the lowest level of pagetable pages. This was obstructing SLUB on PowerPC, which uses kmem_caches for its pagetables. So convert its pte level to use normal gfp pages (whereas pmd, pud and 64k-page pgd want partpages, so continue to use kmem_caches for pmd, pud and pgd). Signed-off-by: Hugh Dickins <hugh@veritas.com> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Signed-off-by: Paul Mackerras <paulus@samba.org>
2007-05-02[POWERPC] Remove arch/powerpc's dependence on asm-ppc/pg{alloc,table}.hDavid Gibson
Currently, all 32-bit powerpc platforms use asm-ppc/pgtable.h and asm-ppc/pgalloc.h, even when otherwise compiled with ARCH=powerpc. Those asm-ppc files are a fairly nasty tangle of #ifdefs including a bunch of things which shouldn't be necessary any more in arch/powerpc. Cleaning up that mess is going to take a while, but this patch is a first step. It separates the asm-powerpc/pg{alloc,table}.h into 64 bit and 32 bit versions in asm-powerpc, which the basic .h files in asm-powerpc select based on config. We make a few tiny tweaks to the innards of the files along the way, making the outermost ifdefs (double-inclusion protection and __KERNEL__) a little cleaner, and #including asm-generic/pgtable.h from the top-level asm-powerpc/pgtable.h (since both the old 32-bit and 64-bit versions ended with such an #include). Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Paul Mackerras <paulus@samba.org>