From 74ffa5a3e68504dd289135b1cf0422c19ffb3f2e Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Thu, 29 Apr 2021 22:57:29 -0700 Subject: [PATCH] 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: Christoph Hellwig Acked-by: Daniel Vetter Cc: Jani Nikula Cc: Joonas Lahtinen Cc: Rodrigo Vivi Cc: Chris Wilson Cc: Peter Zijlstra Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/mm.h | 2 ++ mm/memory.c | 53 ++++++++++++++++++++++++++++------------------ 2 files changed, 34 insertions(+), 21 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index 64be3baf861a..a8335cecf706 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -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); diff --git a/mm/memory.c b/mm/memory.c index f95d12032b34..8dc69471be6c 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -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, - 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_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); - if (err) - untrack_pfn(vma, remap_pfn, PAGE_ALIGN(size)); + 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) + 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);