drm/i915/gvt: add KVMGT support

KVMGT is the MPT implementation based on VFIO/KVM. It provides
a kvmgt_mpt ops to gvt for vGPU access mediation, e.g. to
mediate and emulate the MMIO accesses, to inject interrupts
to vGPU user, to intercept the GTT writing and replace it with
DMA-able address, to write-protect guest PPGTT table for
shadowing synchronization, etc. This patch provides the MPT
implementation for GVT, not yet functional due to theabsence
of mdev.

It's built as kvmgt.ko, depends on vfio.ko, kvm.ko and mdev.ko,
and being required by i915.ko. To not introduce hard dependency
in i915.ko, we used indirect symbol reference. But that means
users have to include kvmgt.ko into init ramdisk if their
i915.ko is included.
Signed-off-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Xiaoguang Chen <xiaoguang.chen@intel.com>
Signed-off-by: Jike Song <jike.song@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>

drivers/gpu/drm/i915/Kconfig

@@ -107,6 +107,15 @@ config DRM_I915_GVT
 
 	  If in doubt, say "N".
 
+config DRM_I915_GVT_KVMGT
+	tristate "Enable KVM/VFIO support for Intel GVT-g"
+	depends on DRM_I915_GVT
+	depends on KVM
+	default n
+	help
+	  Choose this option if you want to enable KVMGT support for
+	  Intel GVT-g.
+
 menu "drm/i915 Debugging"
 depends on DRM_I915
 depends on EXPERT

drivers/gpu/drm/i915/gvt/Makefile

@@ -3,5 +3,8 @@ GVT_SOURCE := gvt.o aperture_gm.o handlers.o vgpu.o trace_points.o firmware.o \
 	interrupt.o gtt.o cfg_space.o opregion.o mmio.o display.o edid.o \
 	execlist.o scheduler.o sched_policy.o render.o cmd_parser.o
 
-ccflags-y                      += -I$(src) -I$(src)/$(GVT_DIR) -Wall
-i915-y			       += $(addprefix $(GVT_DIR)/, $(GVT_SOURCE))
+ccflags-y				+= -I$(src) -I$(src)/$(GVT_DIR) -Wall
+i915-y					+= $(addprefix $(GVT_DIR)/, $(GVT_SOURCE))
+
+CFLAGS_kvmgt.o				:= -Wno-unused-function
+obj-$(CONFIG_DRM_I915_GVT_KVMGT)	+= $(GVT_DIR)/kvmgt.o

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

@@ -84,10 +84,12 @@ int intel_gvt_init_host(void)
 				symbol_get(xengt_mpt), "xengt");
 		intel_gvt_host.hypervisor_type = INTEL_GVT_HYPERVISOR_XEN;
 	} else {
+#if IS_ENABLED(CONFIG_DRM_I915_GVT_KVMGT)
 		/* not in Xen. Try KVMGT */
 		intel_gvt_host.mpt = try_then_request_module(
-				symbol_get(kvmgt_mpt), "kvm");
+				symbol_get(kvmgt_mpt), "kvmgt");
 		intel_gvt_host.hypervisor_type = INTEL_GVT_HYPERVISOR_KVM;
+#endif
 	}
 
 	/* Fail to load MPT modules - bail out */

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

@@ -161,6 +161,20 @@ struct intel_vgpu {
 	DECLARE_BITMAP(tlb_handle_pending, I915_NUM_ENGINES);
 	struct i915_gem_context *shadow_ctx;
 	struct notifier_block shadow_ctx_notifier_block;
+
+#if IS_ENABLED(CONFIG_DRM_I915_GVT_KVMGT)
+	struct {
+		struct device *mdev;
+		struct vfio_region *region;
+		int num_regions;
+		struct eventfd_ctx *intx_trigger;
+		struct eventfd_ctx *msi_trigger;
+		struct rb_root cache;
+		struct mutex cache_lock;
+		void *vfio_group;
+		struct notifier_block iommu_notifier;
+	} vdev;
+#endif
 };
 
 struct intel_gvt_gm {