From 667a0a06c99d5291433b869ed35dabdd95ba1453 Mon Sep 17 00:00:00 2001 From: David Vrabel Date: Thu, 18 Dec 2014 14:48:15 +0000 Subject: mm: provide a find_special_page vma operation The optional find_special_page VMA operation is used to lookup the pages backing a VMA. This is useful in cases where the normal mechanisms for finding the page don't work. This is only called if the PTE is special. One use case is a Xen PV guest mapping foreign pages into userspace. In a Xen PV guest, the PTEs contain MFNs so get_user_pages() (for example) must do an MFN to PFN (M2P) lookup before it can get the page. For foreign pages (those owned by another guest) the M2P lookup returns the PFN as seen by the foreign guest (which would be completely the wrong page for the local guest). This cannot be fixed up improving the M2P lookup since one MFN may be mapped onto two or more pages so getting the right page is impossible given just the MFN. Signed-off-by: David Vrabel Acked-by: Andrew Morton --- include/linux/mm.h | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'include/linux') diff --git a/include/linux/mm.h b/include/linux/mm.h index 80fc92a49649..9269af7349fe 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -290,6 +290,14 @@ struct vm_operations_struct { /* called by sys_remap_file_pages() to populate non-linear mapping */ int (*remap_pages)(struct vm_area_struct *vma, unsigned long addr, unsigned long size, pgoff_t pgoff); + + /* + * Called by vm_normal_page() for special PTEs to find the + * page for @addr. This is useful if the default behavior + * (using pte_page()) would not find the correct page. + */ + struct page *(*find_special_page)(struct vm_area_struct *vma, + unsigned long addr); }; struct mmu_gather; -- cgit v1.2.3 From d8ac3dd41aea245f65465449efc35dd3ac71e91d Mon Sep 17 00:00:00 2001 From: Jennifer Herbert Date: Mon, 5 Jan 2015 13:24:09 +0000 Subject: mm: add 'foreign' alias for the 'pinned' page flag The foreign page flag will be used by Xen guests to mark pages that have grant mappings of frames from other (foreign) guests. The foreign flag is an alias for the existing (Xen-specific) pinned flag. This is safe because pinned is only used on pages used for page tables and these cannot also be foreign. Signed-off-by: Jennifer Herbert Acked-by: Andrew Morton Signed-off-by: David Vrabel --- include/linux/page-flags.h | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'include/linux') diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index e1f5fcd79792..5ed7bdaf22d5 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -121,8 +121,12 @@ enum pageflags { PG_fscache = PG_private_2, /* page backed by cache */ /* XEN */ + /* Pinned in Xen as a read-only pagetable page. */ PG_pinned = PG_owner_priv_1, + /* Pinned as part of domain save (see xen_mm_pin_all()). */ PG_savepinned = PG_dirty, + /* Has a grant mapping of another (foreign) domain's page. */ + PG_foreign = PG_owner_priv_1, /* SLOB */ PG_slob_free = PG_private, @@ -215,6 +219,7 @@ __PAGEFLAG(Slab, slab) PAGEFLAG(Checked, checked) /* Used by some filesystems */ PAGEFLAG(Pinned, pinned) TESTSCFLAG(Pinned, pinned) /* Xen */ PAGEFLAG(SavePinned, savepinned); /* Xen */ +PAGEFLAG(Foreign, foreign); /* Xen */ PAGEFLAG(Reserved, reserved) __CLEARPAGEFLAG(Reserved, reserved) PAGEFLAG(SwapBacked, swapbacked) __CLEARPAGEFLAG(SwapBacked, swapbacked) __SETPAGEFLAG(SwapBacked, swapbacked) -- cgit v1.2.3