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

Liang Li
2016-07-27T01:31:18Z

Support the request for vm's free page information, response with
a page bitmap. QEMU can make use of this free page bitmap to speed
up live migration process by skipping process the free pages.

Signed-off-by: Liang Li <liang.z.li@intel.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
Cc: Amit Shah <amit.shah@redhat.com>
---
drivers/virtio/virtio_balloon.c | 104 +++++++++++++++++++++++++++++++++++++---
1 file changed, 98 insertions(+), 6 deletions(-)

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 2d18ff6..5ca4ad3 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -62,10 +62,13 @@ module_param(oom_pages, int, S_IRUSR | S_IWUSR);
MODULE_PARM_DESC(oom_pages, "pages to free on OOM");

extern unsigned long get_max_pfn(void);
+extern int get_free_pages(unsigned long start_pfn, unsigned long end_pfn,
+ unsigned long *bitmap, unsigned long len);
+

struct virtio_balloon {
struct virtio_device *vdev;
- struct virtqueue *inflate_vq, *deflate_vq, *stats_vq;
+ struct virtqueue *inflate_vq, *deflate_vq, *stats_vq, *misc_vq;

/* The balloon servicing is delegated to a freezable workqueue. */
struct work_struct update_balloon_stats_work;
@@ -89,6 +92,8 @@ struct virtio_balloon {
unsigned long pfn_limit;
/* Used to record the processed pfn range */
unsigned long min_pfn, max_pfn, start_pfn, end_pfn;
+ /* Request header */
+ struct balloon_req_hdr req_hdr;
/*
* The pages we've told the Host we're not using are enqueued
* at vb_dev_info->pages list.
@@ -373,6 +378,49 @@ static void update_balloon_stats(struct virtio_balloon *vb)
pages_to_bytes(available));
}

+static void update_free_pages_stats(struct virtio_balloon *vb,
+ unsigned long req_id)
+{
+ struct scatterlist sg_in, sg_out;
+ unsigned long pfn = 0, bmap_len, max_pfn;
+ struct virtqueue *vq = vb->misc_vq;
+ struct balloon_bmap_hdr *hdr = vb->bmap_hdr;
+ int ret = 1;
+
+ 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);
+ 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);
+ if (pfn + vb->pfn_limit > max_pfn)
+ bmap_len = (max_pfn - pfn) / BITS_PER_BYTE;
+ } else
+ hdr->flag = cpu_to_virtio16(vb->vdev,
+ BALLOON_FLAG_CONT);
+ hdr->bmap_len = cpu_to_virtio64(vb->vdev, bmap_len);
+ sg_init_one(&sg_out, hdr,
+ sizeof(struct balloon_bmap_hdr) + bmap_len);
+
+ virtqueue_add_outbuf(vq, &sg_out, 1, vb, GFP_KERNEL);
+ virtqueue_kick(vq);
+ pfn += vb->pfn_limit;
+ }
+
+ sg_init_one(&sg_in, &vb->req_hdr, sizeof(vb->req_hdr));
+ virtqueue_add_inbuf(vq, &sg_in, 1, &vb->req_hdr, GFP_KERNEL);
+ virtqueue_kick(vq);
+ mutex_unlock(&vb->balloon_lock);
+}
+
/*
* While most virtqueues communicate guest-initiated requests to the hypervisor,
* the stats queue operates in reverse. The driver initializes the virtqueue
@@ -511,18 +559,49 @@ static void update_balloon_size_func(struct work_struct *work)
queue_work(system_freezable_wq, work);
}

+static void misc_handle_rq(struct virtio_balloon *vb)
+{
+ struct balloon_req_hdr *ptr_hdr;
+ unsigned int len;
+
+ ptr_hdr = virtqueue_get_buf(vb->misc_vq, &len);
+ if (!ptr_hdr || len != sizeof(vb->req_hdr))
+ return;
+
+ switch (ptr_hdr->cmd) {
+ case BALLOON_GET_FREE_PAGES:
+ update_free_pages_stats(vb, ptr_hdr->param);
+ break;
+ default:
+ break;
+ }
+}
+
+static void misc_request(struct virtqueue *vq)
+{
+ struct virtio_balloon *vb = vq->vdev->priv;
+
+ misc_handle_rq(vb);
+}
+
static int init_vqs(struct virtio_balloon *vb)
{
- struct virtqueue *vqs[3];
- vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request };
- static const char * const names[] = { "inflate", "deflate", "stats" };
+ struct virtqueue *vqs[4];
+ vq_callback_t *callbacks[] = { balloon_ack, balloon_ack,
+ stats_request, misc_request };
+ 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;
+ if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_MISC_VQ))
+ nvqs = 4;
+ else
+ nvqs = virtio_has_feature(vb->vdev,
+ VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2;
err = vb->vdev->config->find_vqs(vb->vdev, nvqs, vqs, callbacks, names);
if (err)
return err;
@@ -543,6 +622,16 @@ static int init_vqs(struct virtio_balloon *vb)
BUG();
virtqueue_kick(vb->stats_vq);
}
+ if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_MISC_VQ)) {
+ struct scatterlist sg_in;
+
+ vb->misc_vq = vqs[3];
+ sg_init_one(&sg_in, &vb->req_hdr, sizeof(vb->req_hdr));
+ if (virtqueue_add_inbuf(vb->misc_vq, &sg_in, 1,
+ &vb->req_hdr, GFP_KERNEL) < 0)
+ BUG();
+ virtqueue_kick(vb->misc_vq);
+ }
return 0;
}

@@ -639,8 +728,10 @@ static int virtballoon_probe(struct virtio_device *vdev)
vb->bmap_hdr = kzalloc(hdr_len + vb->bmap_len, GFP_KERNEL);

/* Clear the feature bit if memory allocation fails */
- if (!vb->bmap_hdr)
+ if (!vb->bmap_hdr) {
__virtio_clear_bit(vdev, VIRTIO_BALLOON_F_PAGE_BITMAP);
+ __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_MISC_VQ);
+ }
else
vb->page_bitmap = vb->bmap_hdr + hdr_len;
mutex_init(&vb->balloon_lock);
@@ -743,6 +834,7 @@ static unsigned int features[] = {
VIRTIO_BALLOON_F_STATS_VQ,
VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
VIRTIO_BALLOON_F_PAGE_BITMAP,
+ VIRTIO_BALLOON_F_MISC_VQ,
};

static struct virtio_driver virtio_balloon_driver = {
--
1.9.1