Re: [RESEND PATCH v3 kernel 2/7] virtio-balloon: define new feature bit and page bitmap head

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 <redacted>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Cornelia Huck <redacted>
Cc: Amit Shah <redacted>
---
 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..d3b182a 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));
 
+/* Page bitmap header structure */
+struct balloon_bmap_hdr {

+	__virtio16 reserved;
+	/* ID of the request */
+	__virtio64 req_id;
+	/* The pfn of 0 bit in the bitmap */
+	__virtio64 start_pfn;
+	/* The length of the bitmap, in bytes */