i915: fix remap_io_sg to verify the pgprot

remap_io_sg claims that the pgprot is pre-verified using an io_mapping,
but actually does not get passed an io_mapping and just uses the pgprot in
the VMA.  Remove the apply_to_page_range abuse and just loop over
remap_pfn_range for each segment.

Note: this could use io_mapping_map_user by passing an iomap to
remap_io_sg if the maintainers can verify that the pgprot in the iomap in
the only caller is indeed the desired one here.

Link: https://lkml.kernel.org/r/20210326055505.1424432-5-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/gpu/drm/i915/i915_mm.c b/drivers/gpu/drm/i915/i915_mm.c
index 9a777b0..4c8cd08 100644 (file)
--- a/drivers/gpu/drm/i915/i915_mm.c
+++ b/drivers/gpu/drm/i915/i915_mm.c
@@ -28,46 +28,10 @@
 
 #include "i915_drv.h"
 
-struct remap_pfn {
-       struct mm_struct *mm;
-       unsigned long pfn;
-       pgprot_t prot;
-
-       struct sgt_iter sgt;
-       resource_size_t iobase;
-};
+#define EXPECTED_FLAGS (VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP)
 
 #define use_dma(io) ((io) != -1)
 
-static inline unsigned long sgt_pfn(const struct remap_pfn *r)
-{
-       if (use_dma(r->iobase))
-               return (r->sgt.dma + r->sgt.curr + r->iobase) >> PAGE_SHIFT;
-       else
-               return r->sgt.pfn + (r->sgt.curr >> PAGE_SHIFT);
-}
-
-static int remap_sg(pte_t *pte, unsigned long addr, void *data)
-{
-       struct remap_pfn *r = data;
-
-       if (GEM_WARN_ON(!r->sgt.sgp))
-               return -EINVAL;
-
-       /* Special PTE are not associated with any struct page */
-       set_pte_at(r->mm, addr, pte,
-                  pte_mkspecial(pfn_pte(sgt_pfn(r), r->prot)));
-       r->pfn++; /* track insertions in case we need to unwind later */
-
-       r->sgt.curr += PAGE_SIZE;
-       if (r->sgt.curr >= r->sgt.max)
-               r->sgt = __sgt_iter(__sg_next(r->sgt.sgp), use_dma(r->iobase));
-
-       return 0;
-}
-
-#define EXPECTED_FLAGS (VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP)
-
 /**
  * remap_io_sg - remap an IO mapping to userspace
  * @vma: user vma to map to
@@ -82,12 +46,7 @@ int remap_io_sg(struct vm_area_struct *vma,
                unsigned long addr, unsigned long size,
                struct scatterlist *sgl, resource_size_t iobase)
 {
-       struct remap_pfn r = {
-               .mm = vma->vm_mm,
-               .prot = vma->vm_page_prot,
-               .sgt = __sgt_iter(sgl, use_dma(iobase)),
-               .iobase = iobase,
-       };
+       unsigned long pfn, len, remapped = 0;
        int err;
 
        /* We rely on prevalidation of the io-mapping to skip track_pfn(). */
@@ -96,11 +55,25 @@ int remap_io_sg(struct vm_area_struct *vma,
        if (!use_dma(iobase))
                flush_cache_range(vma, addr, size);
 
-       err = apply_to_page_range(r.mm, addr, size, remap_sg, &r);
-       if (unlikely(err)) {
-               zap_vma_ptes(vma, addr, r.pfn << PAGE_SHIFT);
-               return err;
-       }
-
-       return 0;
+       do {
+               if (use_dma(iobase)) {
+                       if (!sg_dma_len(sgl))
+                               break;
+                       pfn = (sg_dma_address(sgl) + iobase) >> PAGE_SHIFT;
+                       len = sg_dma_len(sgl);
+               } else {
+                       pfn = page_to_pfn(sg_page(sgl));
+                       len = sgl->length;
+               }
+
+               err = remap_pfn_range(vma, addr + remapped, pfn, len,
+                                     vma->vm_page_prot);
+               if (err)
+                       break;
+               remapped += len;
+       } while ((sgl = __sg_next(sgl)));
+
+       if (err)
+               zap_vma_ptes(vma, addr, remapped);
+       return err;
 }