Commit 74ffa5a3 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Linus Torvalds
Browse files

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@lst.de
Link: https://lkml.kernel.org/r/20210326055505.1424432-2-hch@lst.de


Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Acked-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent f9001107

include/linux/mm.h

+2 −0
Original line number Diff line number Diff line
@@ -2732,6 +2732,8 @@ 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);

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);

mm/memory.c

+31 −20
Original line number Diff line number Diff line
@@ -2260,26 +2260,17 @@ static inline int remap_p4d_range(struct mm_struct *mm, pgd_t *pgd, 
	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,

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_struct *vma, unsigned long addr, 
		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_struct *vma, unsigned long addr, 
		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);