drm/i915: Introduce remap_io_sg() to prefault discontiguous objects

Provide a way to set the PTE within apply_page_range for discontiguous
objects in addition to the existing method of just incrementing the pfn
for a page range.

Fixes: cc662126b413 ("drm/i915: Introduce DRM_I915_GEM_MMAP_OFFSET")
Signed-off-by: Abdiel Janulgue <abdiel.janulgue@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20191231200356.409475-1-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_mman.c b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
index 879fff8..905527c 100644 (file)
--- a/drivers/gpu/drm/i915/gem/i915_gem_mman.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
@@ -236,42 +236,34 @@ static vm_fault_t vm_fault_cpu(struct vm_fault *vmf)
        struct vm_area_struct *area = vmf->vma;
        struct i915_mmap_offset *mmo = area->vm_private_data;
        struct drm_i915_gem_object *obj = mmo->obj;
-       unsigned long i, size = area->vm_end - area->vm_start;
-       bool write = area->vm_flags & VM_WRITE;
-       vm_fault_t ret = VM_FAULT_SIGBUS;
        int err;
 
-       if (!i915_gem_object_has_struct_page(obj))
-               return ret;
+       if (unlikely(!i915_gem_object_has_struct_page(obj)))
+               return VM_FAULT_SIGBUS;
 
        /* Sanity check that we allow writing into this object */
-       if (i915_gem_object_is_readonly(obj) && write)
-               return ret;
+       if (unlikely(i915_gem_object_is_readonly(obj) &&
+                    area->vm_flags & VM_WRITE))
+               return VM_FAULT_SIGBUS;
 
        err = i915_gem_object_pin_pages(obj);
        if (err)
-               return i915_error_to_vmf_fault(err);
+               goto out;
 
        /* PTEs are revoked in obj->ops->put_pages() */
-       for (i = 0; i < size >> PAGE_SHIFT; i++) {
-               struct page *page = i915_gem_object_get_page(obj, i);
-
-               ret = vmf_insert_pfn(area,
-                                    (unsigned long)area->vm_start + i * PAGE_SIZE,
-                                    page_to_pfn(page));
-               if (ret != VM_FAULT_NOPAGE)
-                       break;
-       }
+       err = remap_io_sg_page(area,
+                              area->vm_start, area->vm_end - area->vm_start,
+                              obj->mm.pages->sgl);
 
-       if (write) {
+       if (area->vm_flags & VM_WRITE) {
                GEM_BUG_ON(!i915_gem_object_has_pinned_pages(obj));
-               obj->cache_dirty = true; /* XXX flush after PAT update? */
                obj->mm.dirty = true;
        }
 
        i915_gem_object_unpin_pages(obj);
 
-       return ret;
+out:
+       return i915_error_to_vmf_fault(err);
 }
 
 static vm_fault_t vm_fault_gtt(struct vm_fault *vmf)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index b7f122d..c234827 100644 (file)
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2015,6 +2015,9 @@ int i915_reg_read_ioctl(struct drm_device *dev, void *data,
 int remap_io_mapping(struct vm_area_struct *vma,
                     unsigned long addr, unsigned long pfn, unsigned long size,
                     struct io_mapping *iomap);
+int remap_io_sg_page(struct vm_area_struct *vma,
+                    unsigned long addr, unsigned long size,
+                    struct scatterlist *sgl);
 
 static inline int intel_hws_csb_write_index(struct drm_i915_private *i915)
 {

diff --git a/drivers/gpu/drm/i915/i915_mm.c b/drivers/gpu/drm/i915/i915_mm.c
index 318562c..2998689 100644 (file)
--- a/drivers/gpu/drm/i915/i915_mm.c
+++ b/drivers/gpu/drm/i915/i915_mm.c
@@ -33,6 +33,8 @@ struct remap_pfn {
        struct mm_struct *mm;
        unsigned long pfn;
        pgprot_t prot;
+
+       struct sgt_iter sgt;
 };
 
 static int remap_pfn(pte_t *pte, unsigned long addr, void *data)
@@ -46,6 +48,30 @@ static int remap_pfn(pte_t *pte, unsigned long addr, void *data)
        return 0;
 }
 
+static inline unsigned long sgt_pfn(const struct sgt_iter *sgt)
+{
+       return sgt->pfn + (sgt->curr >> PAGE_SHIFT);
+}
+
+static int remap_sg_page(pte_t *pte, unsigned long addr, void *data)
+{
+       struct remap_pfn *r = data;
+
+       if (GEM_WARN_ON(!r->sgt.pfn))
+               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->sgt), 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), false);
+
+       return 0;
+}
+
 /**
  * remap_io_mapping - remap an IO mapping to userspace
  * @vma: user vma to map to
@@ -80,3 +106,36 @@ int remap_io_mapping(struct vm_area_struct *vma,
 
        return 0;
 }
+
+/**
+ * remap_io_sg_page - remap an IO mapping to userspace
+ * @vma: user vma to map to
+ * @addr: target user address to start at
+ * @size: size of map area
+ * @sgl: Start sg entry
+ *
+ *  Note: this is only safe if the mm semaphore is held when called.
+ */
+int remap_io_sg_page(struct vm_area_struct *vma,
+                    unsigned long addr, unsigned long size,
+                    struct scatterlist *sgl)
+{
+       struct remap_pfn r = {
+               .mm = vma->vm_mm,
+               .prot = vma->vm_page_prot,
+               .sgt = __sgt_iter(sgl, false),
+       };
+       int err;
+
+       /* We rely on prevalidation of the io-mapping to skip track_pfn(). */
+       GEM_BUG_ON((vma->vm_flags & EXPECTED_FLAGS) != EXPECTED_FLAGS);
+
+       flush_cache_range(vma, addr, size);
+       err = apply_to_page_range(r.mm, addr, size, remap_sg_page, &r);
+       if (unlikely(err)) {
+               zap_vma_ptes(vma, addr, r.pfn << PAGE_SHIFT);
+               return err;
+       }
+
+       return 0;
+}