The patch titled
Subject: mm: add remap_pfn_range_notrack
has been added to the -mm tree. Its filename is
mm-add-remap_pfn_range_notrack.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-add-remap_pfn_range_notrack.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-add-remap_pfn_range_notrack.patch
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The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Christoph Hellwig <hch@xxxxxx>
Subject: mm: add remap_pfn_range_notrack
Patch series "add remap_pfn_range_notrack instead of reinventing it in i915", v2.
i915 has some reason to want to avoid the track_pfn_remap overhead in
remap_pfn_range. Add a function to the core VM to do just that rather
than reinventing the functionality poorly in the driver.
Note that the remap_io_sg path does get exercises when using Xorg on my
Thinkpad X1, so this should be considered lightly tested, I've not managed
to hit the remap_io_mapping path at all.
This patch (of 4):
Add a version of remap_pfn_range that does not call track_pfn_range. This
will be used to fix horrible abuses of VM internals in the i915 driver.
Link: https://lkml.kernel.org/r/20210326055505.1424432-1-hch@xxxxxx
Link: https://lkml.kernel.org/r/20210326055505.1424432-2-hch@xxxxxx
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Cc: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx>
Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
Cc: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/mm.h | 2 +
mm/memory.c | 51 ++++++++++++++++++++++++++-----------------
2 files changed, 33 insertions(+), 20 deletions(-)
--- a/include/linux/mm.h~mm-add-remap_pfn_range_notrack
+++ a/include/linux/mm.h
@@ -2722,6 +2722,8 @@ unsigned long change_prot_numa(struct vm
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);
+int remap_pfn_range_notrack(struct vm_area_struct *vma, unsigned long addr,
+ unsigned long pfn, unsigned long size, pgprot_t prot);
int vm_insert_page(struct vm_area_struct *, unsigned long addr, struct page *);
int vm_insert_pages(struct vm_area_struct *vma, unsigned long addr,
struct page **pages, unsigned long *num);
--- a/mm/memory.c~mm-add-remap_pfn_range_notrack
+++ a/mm/memory.c
@@ -2260,26 +2260,17 @@ static inline int remap_p4d_range(struct
return 0;
}
-/**
- * remap_pfn_range - remap kernel memory to userspace
- * @vma: user vma to map to
- * @addr: target page aligned user address to start at
- * @pfn: page frame number of kernel physical memory address
- * @size: size of mapping area
- * @prot: page protection flags for this mapping
- *
- * Note: this is only safe if the mm semaphore is held when called.
- *
- * Return: %0 on success, negative error code otherwise.
+/*
+ * Variant of remap_pfn_range that does not call track_pfn_remap. The caller
+ * must have pre-validated the caching bits of the pgprot_t.
*/
-int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,
- unsigned long pfn, unsigned long size, pgprot_t prot)
+int remap_pfn_range_notrack(struct vm_area_struct *vma, unsigned long addr,
+ unsigned long pfn, unsigned long size, pgprot_t prot)
{
pgd_t *pgd;
unsigned long next;
unsigned long end = addr + PAGE_ALIGN(size);
struct mm_struct *mm = vma->vm_mm;
- unsigned long remap_pfn = pfn;
int err;
if (WARN_ON_ONCE(!PAGE_ALIGNED(addr)))
@@ -2309,10 +2300,6 @@ int remap_pfn_range(struct vm_area_struc
vma->vm_pgoff = pfn;
}
- err = track_pfn_remap(vma, &prot, remap_pfn, addr, PAGE_ALIGN(size));
- if (err)
- return -EINVAL;
-
vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP;
BUG_ON(addr >= end);
@@ -2324,12 +2311,36 @@ int remap_pfn_range(struct vm_area_struc
err = remap_p4d_range(mm, pgd, addr, next,
pfn + (addr >> PAGE_SHIFT), prot);
if (err)
- break;
+ return err;
} while (pgd++, addr = next, addr != end);
+ return 0;
+}
+
+/**
+ * remap_pfn_range - remap kernel memory to userspace
+ * @vma: user vma to map to
+ * @addr: target page aligned user address to start at
+ * @pfn: page frame number of kernel physical memory address
+ * @size: size of mapping area
+ * @prot: page protection flags for this mapping
+ *
+ * Note: this is only safe if the mm semaphore is held when called.
+ *
+ * Return: %0 on success, negative error code otherwise.
+ */
+int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,
+ unsigned long pfn, unsigned long size, pgprot_t prot)
+{
+ int err;
+
+ err = track_pfn_remap(vma, &prot, pfn, addr, PAGE_ALIGN(size));
if (err)
- untrack_pfn(vma, remap_pfn, PAGE_ALIGN(size));
+ return -EINVAL;
+ err = remap_pfn_range_notrack(vma, addr, pfn, size, prot);
+ if (err)
+ untrack_pfn(vma, pfn, PAGE_ALIGN(size));
return err;
}
EXPORT_SYMBOL(remap_pfn_range);
_
Patches currently in -mm which might be from hch@xxxxxx are
mm-add-remap_pfn_range_notrack.patch
mm-add-a-io_mapping_map_user-helper.patch
i915-use-io_mapping_map_user.patch
i915-fix-remap_io_sg-to-verify-the-pgprot.patch
samples-vfio-mdev-mdpy-use-remap_vmalloc_range.patch
mm-unexport-remap_vmalloc_range_partial.patch
