[WIP] Support VirGL

Follow the installation guide from:
https://gitlab.freedesktop.org/virgl/virglrenderer

Prerequisite:
`sudo apt install libepoxy-dev`

Makefile

@@ -60,6 +60,15 @@ ifneq ($(UNAME_S),Linux)
     ENABLE_VIRTIOGPU := 0
 endif
 
+# VirGL
+ENABLE_VIRGL ?= 1
+ifneq (ENABLE_VIRTIOGPU,0)
+    CFLAGS += $(shell pkg-config virglrenderer --cflags)
+    LDFLAGS += $(shell pkg-config virglrenderer --libs)
+endif
+
+$(call set-feature, VIRGL)
+
 # SDL2
 ENABLE_SDL ?= 1
 ifeq (, $(shell which sdl2-config))

device.h

@@ -219,6 +219,8 @@ void virtio_gpu_write(hart_t *vm,
                       uint8_t width,
                       uint32_t value);
 
+void semu_virgl_init(void);
+
 void virtio_gpu_init(virtio_gpu_state_t *vgpu);
 void virtio_gpu_add_scanout(virtio_gpu_state_t *vgpu,
                             uint32_t width,

feature.h

@@ -17,6 +17,11 @@
 #define SEMU_FEATURE_VIRTIOGPU 1
 #endif
 
+/* VirGL */
+#ifndef SEMU_FEATURE_VIRGL
+#define SEMU_FEATURE_VIRGL 1
+#endif
+
 /* virtio-input */
 #ifndef SEMU_FEATURE_VIRTIOINPUT
 #define SEMU_FEATURE_VIRTIOINPUT 1

main.c

@@ -660,6 +660,8 @@ static int semu_start(int argc, char **argv)
     virtio_input_init(&(emu.vmouse));
 #endif
 #if SEMU_HAS(VIRTIOGPU)
+    semu_virgl_init();
+
     emu.vgpu.ram = emu.ram;
     virtio_gpu_init(&(emu.vgpu));
     virtio_gpu_add_scanout(&(emu.vgpu), 1024, 768);