[Qemu-devel] [PATCH kernel v5 2/5] virtio-balloon: define new feature bit and head struct

[Liang Li]

Add a new feature which supports sending the page information with
a bitmap. The current implementation uses PFNs array, which is not
very efficient. Using bitmap can improve the performance of
inflating/deflating significantly

The page bitmap header will used to tell the host some information
about the page bitmap. e.g. the page size, page bitmap length and
start pfn.

Signed-off-by: Liang Li <address@hidden>
Cc: Michael S. Tsirkin <address@hidden>
Cc: Paolo Bonzini <address@hidden>
Cc: Cornelia Huck <address@hidden>
Cc: Amit Shah <address@hidden>
Cc: Dave Hansen <address@hidden>
---
 include/uapi/linux/virtio_balloon.h | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/include/uapi/linux/virtio_balloon.h 
b/include/uapi/linux/virtio_balloon.h
index 343d7dd..1be4b1f 100644
--- a/include/uapi/linux/virtio_balloon.h
+++ b/include/uapi/linux/virtio_balloon.h
@@ -34,6 +34,7 @@
 #define VIRTIO_BALLOON_F_MUST_TELL_HOST        0 /* Tell before reclaiming 
pages */
 #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_PAGE_BITMAP   3 /* Send page info with bitmap */
 
 /* Size of a PFN in the balloon interface. */
 #define VIRTIO_BALLOON_PFN_SHIFT 12
@@ -82,4 +83,22 @@ struct virtio_balloon_stat {
        __virtio64 val;
 } __attribute__((packed));
 
+/* Response header structure */
+struct virtio_balloon_resp_hdr {
+       __le64 cmd : 8; /* Distinguish different requests type */
+       __le64 flag: 8; /* Mark status for a specific request type */
+       __le64 id : 16; /* Distinguish requests of a specific type */
+       __le64 data_len: 32; /* Length of the following data, in bytes */
+};
+
+/* Page bitmap header structure */
+struct virtio_balloon_bmap_hdr {
+       struct {
+               __le64 start_pfn : 52; /* start pfn for the bitmap */
+               __le64 page_shift : 6; /* page shift width, in bytes */
+               __le64 bmap_len : 6;  /* bitmap length, in bytes */
+       } head;
+       __le64 bmap[0];
+};
+
 #endif /* _LINUX_VIRTIO_BALLOON_H */
-- 
1.8.3.1