[Intel-gfx] [PATCH v2] agp/intel: Serialise after GTT updates

[shuang.he at intel.com]

Tested-By: PRC QA PRTS (Patch Regression Test System Contact: shuang.he at intel.com)
Task id: 5643
-------------------------------------Summary-------------------------------------
Platform          Delta          drm-intel-nightly          Series Applied
PNV                 -1              353/353              352/353
ILK                                  353/353              353/353
SNB                                  400/422              400/422
IVB              +1-1              485/487              485/487
BYT                                  296/296              296/296
HSW              +1-2              507/508              506/508
BDW                 -3              401/402              398/402
-------------------------------------Detailed-------------------------------------
Platform  Test                                drm-intel-nightly          Series Applied
*PNV  igt_gem_concurrent_blit_cpu-bcs-overwrite-source-interruptible      PASS(2, M25)      NO_RESULT(1, M25)
 IVB  igt_gem_storedw_batches_loop_normal      DMESG_WARN(2, M34M4)PASS(5, M34M4M21)      PASS(1, M34)
*IVB  igt_gem_userptr_blits_forked-unsync-swapping-mempressure-interruptible      PASS(2, M34)      NO_RESULT(1, M34)
 HSW  igt_gem_pwrite_pread_snooped-pwrite-blt-cpu_mmap-performance      DMESG_WARN(1, M40)PASS(7, M40M20)      PASS(1, M20)
 HSW  igt_gem_storedw_loop_vebox      DMESG_WARN(1, M20)PASS(2, M40M20)      DMESG_WARN(1, M20)
*HSW  igt_kms_flip_nonexisting-fb      PASS(2, M40M20)      NO_RESULT(1, M20)
*BDW  igt_template_B      PASS(2, M30M28)      NO_RESULT(1, M28)
 BDW  igt_gem_pwrite_pread_display-pwrite-blt-gtt_mmap-performance      DMESG_WARN(1, M28)PASS(1, M30)      DMESG_WARN(1, M28)
*BDW  igt_gem_pwrite_pread_uncached-pwrite-blt-gtt_mmap-performance      PASS(2, M30M28)      DMESG_WARN(1, M28)
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