Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1291439

[PATCH v2 2/6] mm: Add vm_insert_pfn_prot

Show all headers | View raw

The x86 vvar vma conntains pages with differing cacheability
flags.  x86 currently implements this by manually inserting all the ptes
using (io_)remap_pfn_range when the vma is set up.

x86 wants to move to using .fault with VM_FAULT_NOPAGE to set up the
mappings as needed.  The correct API to use to insert a pfn in
.fault is vm_insert_pfn, but vm_insert_pfn can't override the vma's
cache mode, and the HPET page in particular needs to be uncached
despite the fact that the rest of the VMA is cached.

Add vm_insert_pfn_prot to support varying cacheability within the
same non-COW VMA in a more sane manner.

x86 could alternatively use multiple VMAs, but that's messy, would
break CRIU, and would create unnecessary VMAs that would waste
memory.

Acked-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
---

Notes:
    Changes from v1:
     - Improve the changelog (akpm)

 include/linux/mm.h |  2 ++
 mm/memory.c        | 25 +++++++++++++++++++++++--
 2 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 00bad7793788..87ef1d7730ba 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2080,6 +2080,8 @@ int remap_pfn_range(struct vm_area_struct *, unsigned long addr,
 int vm_insert_page(struct vm_area_struct *, unsigned long addr, struct page *);
 int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
 			unsigned long pfn);
+int vm_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,
+			unsigned long pfn, pgprot_t pgprot);
 int vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
 			unsigned long pfn);
 int vm_iomap_memory(struct vm_area_struct *vma, phys_addr_t start, unsigned long len);
diff --git a/mm/memory.c b/mm/memory.c
index c387430f06c3..a29f0b90fc56 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1564,8 +1564,29 @@ out:
 int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
 			unsigned long pfn)
 {
+	return vm_insert_pfn_prot(vma, addr, pfn, vma->vm_page_prot);
+}
+EXPORT_SYMBOL(vm_insert_pfn);
+
+/**
+ * vm_insert_pfn_prot - insert single pfn into user vma with specified pgprot
+ * @vma: user vma to map to
+ * @addr: target user address of this page
+ * @pfn: source kernel pfn
+ * @pgprot: pgprot flags for the inserted page
+ *
+ * This is exactly like vm_insert_pfn, except that it allows drivers to
+ * to override pgprot on a per-page basis.
+ *
+ * This only makes sense for IO mappings, and it makes no sense for
+ * cow mappings.  In general, using multiple vmas is preferable;
+ * vm_insert_pfn_prot should only be used if using multiple VMAs is
+ * impractical.
+ */
+int vm_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,
+			unsigned long pfn, pgprot_t pgprot)
+{
 	int ret;
-	pgprot_t pgprot = vma->vm_page_prot;
 	/*
 	 * Technically, architectures with pte_special can avoid all these
 	 * restrictions (same for remap_pfn_range).  However we would like
@@ -1587,7 +1608,7 @@ int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
 
 	return ret;
 }
-EXPORT_SYMBOL(vm_insert_pfn);
+EXPORT_SYMBOL(vm_insert_pfn_prot);
 
 int vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
 			unsigned long pfn)
-- 
2.5.0

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[PATCH v2 0/6] mm, x86/vdso: Special IO mapping improvements Andy Lutomirski <luto@kernel.org> - 2015-12-14 19:40 +0100
  [PATCH v2 2/6] mm: Add vm_insert_pfn_prot Andy Lutomirski <luto@kernel.org> - 2015-12-14 19:40 +0100
  [PATCH v2 4/6] x86,vdso: Use .fault for the vdso text mapping Andy Lutomirski <luto@kernel.org> - 2015-12-14 19:40 +0100
  [PATCH v2 3/6] x86/vdso: Track each mm's loaded vdso image as well as its base Andy Lutomirski <luto@kernel.org> - 2015-12-14 19:40 +0100
  Re: [PATCH v2 0/6] mm, x86/vdso: Special IO mapping improvements Andy Lutomirski <luto@amacapital.net> - 2015-12-24 01:00 +0100
    Re: [PATCH v2 0/6] mm, x86/vdso: Special IO mapping improvements Andy Lutomirski <luto@amacapital.net> - 2015-12-29 14:20 +0100

csiph-web