This is similar to remap_pfn_range(), and uses the recently refactor
code to do the page table walking. The key difference is that is back
propagates its error as this is required for use from within a pagefault
handler. The other difference, is that it combine the page protection
from io-mapping, which is known from when the io-mapping is created,
with the per-vma page protection flags. This avoids having to walk the
entire system description to rediscover the special page protection
established for the io-mapping.
Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
Cc: Andrew Morton <a...@linux-foundation.org>
Cc: "Kirill A. Shutemov" <kirill.shute...@linux.intel.com>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Rik van Riel <r...@redhat.com>
Cc: Mel Gorman <mgor...@suse.de>
Cc: Cyrill Gorcunov <gorcu...@gmail.com>
Cc: Johannes Weiner <han...@cmpxchg.org>
Cc: linux...@kvack.org
---
include/linux/mm.h | 4 ++++
mm/memory.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 50 insertions(+)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 47a93928b90f..3dfecd58adb0 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2083,6 +2083,10 @@ unsigned long change_prot_numa(struct vm_area_struct
*vma,
struct vm_area_struct *find_extend_vma(struct mm_struct *, unsigned long addr);
int remap_pfn_range(struct vm_area_struct *, unsigned long addr,
unsigned long pfn, unsigned long size, pgprot_t);
+struct io_mapping;
+int remap_io_mapping(struct vm_area_struct *,
+ unsigned long addr, unsigned long pfn, unsigned long size,
+ struct io_mapping *iomap);
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);
diff --git a/mm/memory.c b/mm/memory.c
index acb06f40d614..83bc5df3fafc 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -61,6 +61,7 @@
#include <linux/string.h>
#include <linux/dma-debug.h>
#include <linux/debugfs.h>
+#include <linux/io-mapping.h>
#include <asm/io.h>
#include <asm/pgalloc.h>
@@ -1762,6 +1763,51 @@ int remap_pfn_range(struct vm_area_struct *vma, unsigned
long addr,
EXPORT_SYMBOL(remap_pfn_range);
/**
+ * remap_io_mapping - remap an IO mapping to userspace
+ * @vma: user vma to map to
+ * @addr: target user address to start at
+ * @pfn: physical address of kernel memory
+ * @size: size of map area
+ * @iomap: the source io_mapping
+ *
+ * Note: this is only safe if the mm semaphore is held when called.
+ */
+int remap_io_mapping(struct vm_area_struct *vma,
+ unsigned long addr, unsigned long pfn, unsigned long size,
+ struct io_mapping *iomap)
+{
+ unsigned long end = addr + PAGE_ALIGN(size);
+ struct remap_pfn r;
+ pgd_t *pgd;
+ int err;
+
+ if (WARN_ON(addr >= end))
+ return -EINVAL;
+
+#define MUST_SET (VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP)
+ BUG_ON(is_cow_mapping(vma->vm_flags));
+ BUG_ON((vma->vm_flags & MUST_SET) != MUST_SET);
+#undef MUST_SET
+
+ r.mm = vma->vm_mm;
+ r.addr = addr;
+ r.pfn = pfn;
+ r.prot = __pgprot((pgprot_val(iomap->prot) & _PAGE_CACHE_MASK) |
+ (pgprot_val(vma->vm_page_prot) & ~_PAGE_CACHE_MASK));
+
+ pgd = pgd_offset(r.mm, addr);
+ do {
+ err = remap_pud_range(&r, pgd++, pgd_addr_end(r.addr, end));
+ } while (err == 0 && r.addr < end);
+
+ if (err)
+ zap_page_range_single(vma, addr, r.addr - addr, NULL);
+
+ return err;
+}
+EXPORT_SYMBOL(remap_io_mapping);
+
+/**
* vm_iomap_memory - remap memory to userspace
* @vma: user vma to map to
* @start: start of area
--
2.1.4
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