RE: [PATCH v2 repost 7/7] virtio-balloon: tell host vm's free page info

quoted

 }

+static void update_free_pages_stats(struct virtio_balloon *vb,

why _stats?

Will change.

quoted

+	max_pfn = get_max_pfn();
+	mutex_lock(&vb->balloon_lock);
+	while (pfn < max_pfn) {
+		memset(vb->page_bitmap, 0, vb->bmap_len);
+		ret = get_free_pages(pfn, pfn + vb->pfn_limit,
+			vb->page_bitmap, vb->bmap_len * BITS_PER_BYTE);
+		hdr->cmd = cpu_to_virtio16(vb->vdev,

BALLOON_GET_FREE_PAGES);

quoted

+		hdr->page_shift = cpu_to_virtio16(vb->vdev, PAGE_SHIFT);
+		hdr->req_id = cpu_to_virtio64(vb->vdev, req_id);
+		hdr->start_pfn = cpu_to_virtio64(vb->vdev, pfn);
+		bmap_len = vb->pfn_limit / BITS_PER_BYTE;
+		if (!ret) {
+			hdr->flag = cpu_to_virtio16(vb->vdev,
+

	BALLOON_FLAG_DONE);

quoted

+			if (pfn + vb->pfn_limit > max_pfn)
+				bmap_len = (max_pfn - pfn) /

BITS_PER_BYTE;

quoted

+		} else
+			hdr->flag = cpu_to_virtio16(vb->vdev,
+

	BALLOON_FLAG_CONT);

quoted

+		hdr->bmap_len = cpu_to_virtio64(vb->vdev, bmap_len);
+		sg_init_one(&sg_out, hdr,
+			 sizeof(struct balloon_bmap_hdr) + bmap_len);

Wait a second. This adds the same buffer multiple times in a loop.
We will overwrite the buffer without waiting for hypervisor to process it.
What did I miss?

I am no quite sure about this part, I though the virtqueue_kick(vq) will prevent
the buffer from overwrite, I realized it's wrong.

quoted

+
+		virtqueue_add_outbuf(vq, &sg_out, 1, vb, GFP_KERNEL);

this can fail. you want to maybe make sure vq has enough space before you
use it or check error and wait.

quoted

+		virtqueue_kick(vq);

why kick here within loop? wait until done. in fact kick outside lock is better
for smp.

I will change this part in v3.

quoted

+		pfn += vb->pfn_limit;
+	static const char * const names[] = { "inflate", "deflate", "stats",
+						 "misc" };
 	int err, nvqs;

 	/*
 	 * We expect two virtqueues: inflate and deflate, and
 	 * optionally stat.
 	 */
-	nvqs = virtio_has_feature(vb->vdev,

VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2;

quoted

+	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_MISC_VQ))
+		nvqs = 4;

Does misc vq depend on stats vq feature then? if yes please validate that.

Yes, what's you mean by 'validate' that?

quoted

+	else
+		nvqs = virtio_has_feature(vb->vdev,
+					  VIRTIO_BALLOON_F_STATS_VQ) ? 3 :

2;

Replace that ? with else too pls.

Will change.

Thanks!
Liang