drm/i915/gvt: Refine the snapshort range of I915 MCHBAR to optimize gvt-g boot time

Currently it will take the snapshot of the MCHBAR registers for gvt-g
initialization so that it can be used for guest vgpu. And it will cover
from 0x140000 to 0x17ffff. In fact based on the HW spec most of them are
meanlingless and some time is wasted to read these register.
Only the range of 0x144000 to 0x147fff contains the valid definition.
So the range of capturing I915 MCHBAR register is refined, which helps
to optimize the gvt-g boot time.

V1->V2: Move the register definition into reg.h
Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
Acked-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>

drivers/gpu/drm/i915/gvt/handlers.c

@@ -3264,7 +3264,7 @@ void intel_gvt_clean_mmio_info(struct intel_gvt *gvt)
 /* Special MMIO blocks. */
 static struct gvt_mmio_block mmio_blocks[] = {
 	{D_SKL_PLUS, _MMIO(CSR_MMIO_START_RANGE), 0x3000, NULL, NULL},
-	{D_ALL, _MMIO(MCHBAR_MIRROR_BASE_SNB), 0x40000, NULL, NULL},
+	{D_ALL, MCHBAR_MIRROR_REG_BASE, 0x4000, NULL, NULL},
 	{D_ALL, _MMIO(VGT_PVINFO_PAGE), VGT_PVINFO_SIZE,
 		pvinfo_mmio_read, pvinfo_mmio_write},
 	{D_ALL, LGC_PALETTE(PIPE_A, 0), 1024, NULL, NULL},

drivers/gpu/drm/i915/gvt/reg.h

@@ -95,4 +95,7 @@
 #define RING_GFX_MODE(base)	_MMIO((base) + 0x29c)
 #define VF_GUARDBAND		_MMIO(0x83a4)
 
+/* define the effective range of MCHBAR register on Sandybridge+ */
+#define MCHBAR_MIRROR_REG_BASE	_MMIO(MCHBAR_MIRROR_BASE_SNB + 0x4000)
+
 #endif