drm/radeon: Add RADEON_INFO_VA_UNMAP_WORKING query

This tells userspace that it's safe to use the RADEON_VA_UNMAP operation
of the DRM_RADEON_GEM_VA ioctl.

Cc: stable@vger.kernel.org
(NOTE: Backporting this commit requires at least backports of commits
26d4d129b6042197b4cbc8341c0618f99231af2f,
48afbd70ac7b6aa62e8d452091023941d8085f8a and
c29c0876ec05d51a93508a39b90b92c29ba6423d as well, otherwise using
RADEON_VA_UNMAP runs into trouble)

Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>
Signed-off-by: Christian König <christian.koenig@amd.com>

drivers/gpu/drm/radeon/radeon_kms.c

@@ -576,6 +576,9 @@ static int radeon_info_ioctl(struct drm_device *dev, void *data, struct drm_file
 		if (radeon_get_allowed_info_register(rdev, *value, value))
 			return -EINVAL;
 		break;
+	case RADEON_INFO_VA_UNMAP_WORKING:
+		*value = true;
+		break;
 	default:
 		DRM_DEBUG_KMS("Invalid request %d\n", info->request);
 		return -EINVAL;

include/uapi/drm/radeon_drm.h

@@ -1038,6 +1038,7 @@ struct drm_radeon_cs {
 #define RADEON_INFO_CURRENT_GPU_SCLK	0x22
 #define RADEON_INFO_CURRENT_GPU_MCLK	0x23
 #define RADEON_INFO_READ_REG		0x24
+#define RADEON_INFO_VA_UNMAP_WORKING	0x25
 
 struct drm_radeon_info {
 	uint32_t		request;