Revert "drm/vgem: fix cache synchronization on arm/arm64"

commit 7e9e5ead55be ("drm/vgem: fix cache synchronization on arm/arm64")
broke all of the !llc i915-vgem coherency tests in CI, and left the HW
very, very unhappy (which is even more scary).

Fixes: 7e9e5ead55be ("drm/vgem: fix cache synchronization on arm/arm64")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Rob Clark <robdclark@chromium.org>
Cc: Sean Paul <seanpaul@chromium.org>
Acked-by: Sean Paul <sean@poorly.run>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20190801124458.24949-1-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/vgem/vgem_drv.c b/drivers/gpu/drm/vgem/vgem_drv.c
index fc04803..11a8f99 100644 (file)
--- a/drivers/gpu/drm/vgem/vgem_drv.c
+++ b/drivers/gpu/drm/vgem/vgem_drv.c
@@ -47,16 +47,10 @@ static struct vgem_device {
        struct platform_device *platform;
 } *vgem_device;
 
-static void sync_and_unpin(struct drm_vgem_gem_object *bo);
-static struct page **pin_and_sync(struct drm_vgem_gem_object *bo);
-
 static void vgem_gem_free_object(struct drm_gem_object *obj)
 {
        struct drm_vgem_gem_object *vgem_obj = to_vgem_bo(obj);
 
-       if (!obj->import_attach)
-               sync_and_unpin(vgem_obj);
-
        kvfree(vgem_obj->pages);
        mutex_destroy(&vgem_obj->pages_lock);
 
@@ -84,15 +78,40 @@ static vm_fault_t vgem_gem_fault(struct vm_fault *vmf)
                return VM_FAULT_SIGBUS;
 
        mutex_lock(&obj->pages_lock);
-       if (!obj->pages)
-               pin_and_sync(obj);
        if (obj->pages) {
                get_page(obj->pages[page_offset]);
                vmf->page = obj->pages[page_offset];
                ret = 0;
        }
        mutex_unlock(&obj->pages_lock);
+       if (ret) {
+               struct page *page;
+
+               page = shmem_read_mapping_page(
+                                       file_inode(obj->base.filp)->i_mapping,
+                                       page_offset);
+               if (!IS_ERR(page)) {
+                       vmf->page = page;
+                       ret = 0;
+               } else switch (PTR_ERR(page)) {
+                       case -ENOSPC:
+                       case -ENOMEM:
+                               ret = VM_FAULT_OOM;
+                               break;
+                       case -EBUSY:
+                               ret = VM_FAULT_RETRY;
+                               break;
+                       case -EFAULT:
+                       case -EINVAL:
+                               ret = VM_FAULT_SIGBUS;
+                               break;
+                       default:
+                               WARN_ON(PTR_ERR(page));
+                               ret = VM_FAULT_SIGBUS;
+                               break;
+               }
 
+       }
        return ret;
 }
 
@@ -258,93 +277,32 @@ static const struct file_operations vgem_driver_fops = {
        .release        = drm_release,
 };
 
-/* Called under pages_lock, except in free path (where it can't race): */
-static void sync_and_unpin(struct drm_vgem_gem_object *bo)
-{
-       struct drm_device *dev = bo->base.dev;
-
-       if (bo->table) {
-               dma_sync_sg_for_cpu(dev->dev, bo->table->sgl,
-                               bo->table->nents, DMA_BIDIRECTIONAL);
-               sg_free_table(bo->table);
-               kfree(bo->table);
-               bo->table = NULL;
-       }
-
-       if (bo->pages) {
-               drm_gem_put_pages(&bo->base, bo->pages, true, true);
-               bo->pages = NULL;
-       }
-}
-
-static struct page **pin_and_sync(struct drm_vgem_gem_object *bo)
-{
-       struct drm_device *dev = bo->base.dev;
-       int npages = bo->base.size >> PAGE_SHIFT;
-       struct page **pages;
-       struct sg_table *sgt;
-
-       WARN_ON(!mutex_is_locked(&bo->pages_lock));
-
-       pages = drm_gem_get_pages(&bo->base);
-       if (IS_ERR(pages)) {
-               bo->pages_pin_count--;
-               mutex_unlock(&bo->pages_lock);
-               return pages;
-       }
-
-       sgt = drm_prime_pages_to_sg(pages, npages);
-       if (IS_ERR(sgt)) {
-               dev_err(dev->dev,
-                       "failed to allocate sgt: %ld\n",
-                       PTR_ERR(bo->table));
-               drm_gem_put_pages(&bo->base, pages, false, false);
-               mutex_unlock(&bo->pages_lock);
-               return ERR_CAST(bo->table);
-       }
-
-       /*
-        * Flush the object from the CPU cache so that importers
-        * can rely on coherent indirect access via the exported
-        * dma-address.
-        */
-       dma_sync_sg_for_device(dev->dev, sgt->sgl,
-                       sgt->nents, DMA_BIDIRECTIONAL);
-
-       bo->pages = pages;
-       bo->table = sgt;
-
-       return pages;
-}
-
 static struct page **vgem_pin_pages(struct drm_vgem_gem_object *bo)
 {
-       struct page **pages;
-
        mutex_lock(&bo->pages_lock);
-       if (bo->pages_pin_count++ == 0 && !bo->pages) {
-               pages = pin_and_sync(bo);
-       } else {
-               WARN_ON(!bo->pages);
-               pages = bo->pages;
+       if (bo->pages_pin_count++ == 0) {
+               struct page **pages;
+
+               pages = drm_gem_get_pages(&bo->base);
+               if (IS_ERR(pages)) {
+                       bo->pages_pin_count--;
+                       mutex_unlock(&bo->pages_lock);
+                       return pages;
+               }
+
+               bo->pages = pages;
        }
        mutex_unlock(&bo->pages_lock);
 
-       return pages;
+       return bo->pages;
 }
 
 static void vgem_unpin_pages(struct drm_vgem_gem_object *bo)
 {
-       /*
-        * We shouldn't hit this for imported bo's.. in the import
-        * case we don't own the scatter-table
-        */
-       WARN_ON(bo->base.import_attach);
-
        mutex_lock(&bo->pages_lock);
        if (--bo->pages_pin_count == 0) {
-               WARN_ON(!bo->table);
-               sync_and_unpin(bo);
+               drm_gem_put_pages(&bo->base, bo->pages, true, true);
+               bo->pages = NULL;
        }
        mutex_unlock(&bo->pages_lock);
 }
@@ -352,12 +310,18 @@ static void vgem_unpin_pages(struct drm_vgem_gem_object *bo)
 static int vgem_prime_pin(struct drm_gem_object *obj)
 {
        struct drm_vgem_gem_object *bo = to_vgem_bo(obj);
+       long n_pages = obj->size >> PAGE_SHIFT;
        struct page **pages;
 
        pages = vgem_pin_pages(bo);
        if (IS_ERR(pages))
                return PTR_ERR(pages);
 
+       /* Flush the object from the CPU cache so that importers can rely
+        * on coherent indirect access via the exported dma-address.
+        */
+       drm_clflush_pages(pages, n_pages);
+
        return 0;
 }