[PATCH v7 kernel 4/5] virtio-balloon: define flags and head for host request vq

[Wei Wang]

From: Liang Li <liang.z.li@xxxxxxxxx>

Define the flags and head struct for a new host request virtual
queue. Guest can get requests from host and then responds to
them on this new virtual queue.
Host can make use of this virtqueue to request the guest to do
some operations, e.g. drop page cache, synchronize file system,
etc. The hypervisor can get some of guest's runtime information
through this virtual queue too, e.g. the guest's unused page
information, which can be used for live migration optimization.

Signed-off-by: Liang Li <liang.z.li@xxxxxxxxx>
Signed-off-by: Wei Wang <wei.w.wang@xxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Michael S. Tsirkin <mst@xxxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: Cornelia Huck <cornelia.huck@xxxxxxxxxx>
Cc: Amit Shah <amit.shah@xxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Liang Li <liliang324@xxxxxxxxx>
Cc: Wei Wang <wei.w.wang@xxxxxxxxx>
---
 include/uapi/linux/virtio_balloon.h | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/include/uapi/linux/virtio_balloon.h b/include/uapi/linux/virtio_balloon.h
index ed627b2..630b0ef 100644
--- a/include/uapi/linux/virtio_balloon.h
+++ b/include/uapi/linux/virtio_balloon.h
@@ -35,6 +35,7 @@
 #define VIRTIO_BALLOON_F_STATS_VQ	1 /* Memory Stats virtqueue */
 #define VIRTIO_BALLOON_F_DEFLATE_ON_OOM	2 /* Deflate balloon on OOM */
 #define VIRTIO_BALLOON_F_CHUNK_TRANSFER	3 /* Transfer pages in chunks */
+#define VIRTIO_BALLOON_F_HOST_REQ_VQ	4 /* Host request virtqueue */
 
 /* Size of a PFN in the balloon interface. */
 #define VIRTIO_BALLOON_PFN_SHIFT 12
@@ -94,4 +95,25 @@ struct virtio_balloon_resp_hdr {
 	__le32 data_len; /* Payload len in bytes */
 };
 
+enum virtio_balloon_req_id {
+	/* Get unused page information */
+	BALLOON_GET_UNUSED_PAGES,
+};
+
+enum virtio_balloon_flag {
+	/* Have more data for a request */
+	BALLOON_FLAG_CONT,
+	/* No more data for a request */
+	BALLOON_FLAG_DONE,
+};
+
+struct virtio_balloon_req_hdr {
+	/* Used to distinguish different requests */
+	__le16 cmd;
+	/* Reserved */
+	__le16 reserved[3];
+	/* Request parameter */
+	__le64 param;
+};
+
 #endif /* _LINUX_VIRTIO_BALLOON_H */
-- 
2.7.4