[PATCH 25/25] Revert "i915: fix remap_io_sg to verify the pgprot"

[Matthew Auld]

This reverts commit b12d691ea5e01db42ccf3b4207e57cb3ce7cfe91.
---
 drivers/gpu/drm/i915/i915_mm.c | 73 +++++++++++++++++++++++-----------
 1 file changed, 50 insertions(+), 23 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_mm.c b/drivers/gpu/drm/i915/i915_mm.c
index 4c8cd08c672d..9a777b0ff59b 100644
--- a/drivers/gpu/drm/i915/i915_mm.c
+++ b/drivers/gpu/drm/i915/i915_mm.c
@@ -28,10 +28,46 @@
 
 #include "i915_drv.h"
 
-#define EXPECTED_FLAGS (VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP)
+struct remap_pfn {
+	struct mm_struct *mm;
+	unsigned long pfn;
+	pgprot_t prot;
+
+	struct sgt_iter sgt;
+	resource_size_t iobase;
+};
 
 #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
@@ -46,7 +82,12 @@ int remap_io_sg(struct vm_area_struct *vma,
 		unsigned long addr, unsigned long size,
 		struct scatterlist *sgl, resource_size_t iobase)
 {
-	unsigned long pfn, len, remapped = 0;
+	struct remap_pfn r = {
+		.mm = vma->vm_mm,
+		.prot = vma->vm_page_prot,
+		.sgt = __sgt_iter(sgl, use_dma(iobase)),
+		.iobase = iobase,
+	};
 	int err;
 
 	/* We rely on prevalidation of the io-mapping to skip track_pfn(). */
@@ -55,25 +96,11 @@ int remap_io_sg(struct vm_area_struct *vma,
 	if (!use_dma(iobase))
 		flush_cache_range(vma, addr, size);
 
-	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;
+	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;
 }
-- 
2.26.3