drm/vmwgfx: Add a cpu blit utility that can be used for page-backed bos

The utility uses kmap_atomic() instead of vmapping the whole buffer object. As a result there will be more book-keeping but on some architectures this will help avoid exhausting vmalloc space and also avoid expensive TLB flushes.

The blit utility also adds a provision to compute a bounding box of changed content, which is very useful to optimize presentation speed of ill-behaved applications that don't supply proper damage regions, and for page-flips. The cost of computing the bounding box is not that expensive when done in a cpu-blit utility like this.

---
v2: Fix a compilation failure by replacing a struct vmw_diff_cpy member called "memcpy" with "do_cpy".

---
 drivers/gpu/drm/vmwgfx/Makefile      |   2 +-
 drivers/gpu/drm/vmwgfx/vmwgfx_blit.c | 506 +++++++++++++++++++++++++++++++++++
 drivers/gpu/drm/vmwgfx/vmwgfx_drv.h  |  48 ++++
 3 files changed, 555 insertions(+), 1 deletion(-)
 create mode 100644 drivers/gpu/drm/vmwgfx/vmwgfx_blit.c

index ad80211e1098..794cc9d5c9b0 100644
@@ -7,6 +7,6 @@ vmwgfx-y := vmwgfx_execbuf.o vmwgfx_gmr.o vmwgfx_kms.o vmwgfx_drv.o \
 	    vmwgfx_surface.o vmwgfx_prime.o vmwgfx_mob.o vmwgfx_shader.o \
 	    vmwgfx_cmdbuf_res.o vmwgfx_cmdbuf.o vmwgfx_stdu.o \
 	    vmwgfx_cotable.o vmwgfx_so.o vmwgfx_binding.o vmwgfx_msg.o \
-	    vmwgfx_simple_resource.o vmwgfx_va.o
+	    vmwgfx_simple_resource.o vmwgfx_va.o vmwgfx_blit.o
 
 obj-$(CONFIG_DRM_VMWGFX) := vmwgfx.o

2.14.3

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