drm/vmwgfx: Check pin count before attempting to move a buffer

In certain scenarios, e.g. when fbdev is enabled, we can get into
a situation where a vmw_framebuffer_pin() is called on a buffer
that is already pinned.

When this happens, ttm_bo_validate() will unintentially remove the
TTM_PL_FLAG_NO_EVICT flag, thus unpinning it, and leaving no way
to actually pin the buffer again.

To prevent this, if a buffer is already pinned, then instead of
calling ttm_bo_validate(), just make sure the proposed placement is
compatible with the existing placement.

Signed-off-by: Sinclair Yeh <syeh@vmware.com>
Reviewed-by: Thomas Hellstrom <thellstrom@vmware.com>
Cc: <stable@vger.kernel.org>
---
This is the 2nd patch in a 3-patch series to fix a console black
screen issue on Ubuntu 16.04 server.  This fixes a BUG_ON()
condition where a pinned buffer gets accidentally put onto the
LRU list.

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_dmabuf.c b/drivers/gpu/drm/vmwgfx/vmwgfx_dmabuf.c
index 9b078a4939968d8521a96b3f83280f4f06b407bc..0cd889015dc57d5c0d0a8b89f39cd17b10303fbf 100644 (file)
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_dmabuf.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_dmabuf.c
@@ -49,6 +49,7 @@ int vmw_dmabuf_pin_in_placement(struct vmw_private *dev_priv,
 {
        struct ttm_buffer_object *bo = &buf->base;
        int ret;
+       uint32_t new_flags;
 
        ret = ttm_write_lock(&dev_priv->reservation_sem, interruptible);
        if (unlikely(ret != 0))
@@ -60,7 +61,12 @@ int vmw_dmabuf_pin_in_placement(struct vmw_private *dev_priv,
        if (unlikely(ret != 0))
                goto err;
 
-       ret = ttm_bo_validate(bo, placement, interruptible, false);
+       if (buf->pin_count > 0)
+               ret = ttm_bo_mem_compat(placement, &bo->mem,
+                                       &new_flags) == true ? 0 : -EINVAL;
+       else
+               ret = ttm_bo_validate(bo, placement, interruptible, false);
+
        if (!ret)
                vmw_bo_pin_reserved(buf, true);
 
@@ -91,6 +97,7 @@ int vmw_dmabuf_pin_in_vram_or_gmr(struct vmw_private *dev_priv,
 {
        struct ttm_buffer_object *bo = &buf->base;
        int ret;
+       uint32_t new_flags;
 
        ret = ttm_write_lock(&dev_priv->reservation_sem, interruptible);
        if (unlikely(ret != 0))
@@ -102,6 +109,12 @@ int vmw_dmabuf_pin_in_vram_or_gmr(struct vmw_private *dev_priv,
        if (unlikely(ret != 0))
                goto err;
 
+       if (buf->pin_count > 0) {
+               ret = ttm_bo_mem_compat(&vmw_vram_gmr_placement, &bo->mem,
+                                       &new_flags) == true ? 0 : -EINVAL;
+               goto out_unreserve;
+       }
+
        ret = ttm_bo_validate(bo, &vmw_vram_gmr_placement, interruptible,
                              false);
        if (likely(ret == 0) || ret == -ERESTARTSYS)
@@ -161,6 +174,7 @@ int vmw_dmabuf_pin_in_start_of_vram(struct vmw_private *dev_priv,
        struct ttm_placement placement;
        struct ttm_place place;
        int ret = 0;
+       uint32_t new_flags;
 
        place = vmw_vram_placement.placement[0];
        place.lpfn = bo->num_pages;
@@ -185,10 +199,15 @@ int vmw_dmabuf_pin_in_start_of_vram(struct vmw_private *dev_priv,
         */
        if (bo->mem.mem_type == TTM_PL_VRAM &&
            bo->mem.start < bo->num_pages &&
-           bo->mem.start > 0)
+           bo->mem.start > 0 &&
+           buf->pin_count == 0)
                (void) ttm_bo_validate(bo, &vmw_sys_placement, false, false);
 
-       ret = ttm_bo_validate(bo, &placement, interruptible, false);
+       if (buf->pin_count > 0)
+               ret = ttm_bo_mem_compat(&placement, &bo->mem,
+                                       &new_flags) == true ? 0 : -EINVAL;
+       else
+               ret = ttm_bo_validate(bo, &placement, interruptible, false);
 
        /* For some reason we didn't end up at the start of vram */
        WARN_ON(ret == 0 && bo->offset != 0);