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Subject[PATCH 6/6] virtio-balloon: tell host vm's free page info
Date
Support the new request for vm's free page information, response with
a page bitmap. QEMU can make use of this free page bitmap to speed up
the 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: 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 | 64 ++++++++++++++++++++++++++++++++++++++++-
1 file changed, 63 insertions(+), 1 deletion(-)

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 5a30ca0..5237d50 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -46,8 +46,12 @@ static int oom_pages = OOM_VBALLOON_DEFAULT_PAGES;
module_param(oom_pages, int, S_IRUSR | S_IWUSR);
MODULE_PARM_DESC(oom_pages, "pages to free on OOM");

+extern void get_free_pages(unsigned long *free_page_bitmap, unsigned long len);
+extern unsigned long get_max_pfn(void);
+
enum balloon_req_id {
BALLOON_DROP_CACHE,
+ BALLOON_GET_FREE_PAGES,
};

struct balloon_req_hdr {
@@ -85,6 +89,9 @@ struct virtio_balloon {
/* Used to record the processed pfn range */
unsigned long min_pfn, max_pfn, start_pfn, end_pfn;
struct balloon_req_hdr req_hdr;
+ /* Free page bitmap and length to tell the host */
+ unsigned long *free_pages;
+ unsigned long free_bmap_len;
/*
* The pages we've told the Host we're not using are enqueued
* at vb_dev_info->pages list.
@@ -370,6 +377,41 @@ static void update_balloon_stats(struct virtio_balloon *vb)
pages_to_bytes(available));
}

+static int reset_free_page_bmap(struct virtio_balloon *vb,
+ unsigned long *max_pfn)
+{
+ int err = 0;
+ unsigned long bitmap_bytes;
+
+ *max_pfn = get_max_pfn();
+ bitmap_bytes = ALIGN(*max_pfn, BITS_PER_LONG) / BITS_PER_BYTE;
+
+ if (bitmap_bytes < vb->free_bmap_len)
+ memset(vb->free_pages, 0, bitmap_bytes);
+ else {
+ kfree(vb->free_pages);
+ vb->free_bmap_len = bitmap_bytes;
+ vb->free_pages = kzalloc(bitmap_bytes, GFP_KERNEL);
+ }
+
+ if (!vb->free_pages) {
+ err = -ENOMEM;
+ vb->free_bmap_len = 0;
+ }
+
+ return err;
+}
+
+static void update_free_pages_stats(struct virtio_balloon *vb)
+{
+ unsigned long max_pfn;
+
+ if (!reset_free_page_bmap(vb, &max_pfn))
+ get_free_pages(vb->free_pages, max_pfn);
+ else
+ dev_err(&vb->vdev->dev, "%s failure: No memory!\n", __func__);
+}
+
/*
* While most virtqueues communicate guest-initiated requests to the hypervisor,
* the stats queue operates in reverse. The driver initializes the virtqueue
@@ -511,10 +553,11 @@ static void update_balloon_size_func(struct work_struct *work)
static void misc_handle_rq(struct virtio_balloon *vb)
{
struct virtqueue *vq;
- struct scatterlist sg_out;
+ struct scatterlist sg_out, sg[2];
unsigned int len;
struct balloon_req_hdr *ptr_hdr;
struct scatterlist sg_in;
+ struct balloon_bmap_hdr hdr;

vq = vb->misc_vq;
ptr_hdr = virtqueue_get_buf(vq, &len);
@@ -532,6 +575,18 @@ static void misc_handle_rq(struct virtio_balloon *vb)
sg_init_one(&sg_in, &vb->req_hdr, sizeof(vb->req_hdr));
virtqueue_add_inbuf(vq, &sg_in, 1, &vb->req_hdr, GFP_KERNEL);
break;
+ case BALLOON_GET_FREE_PAGES:
+ update_free_pages_stats(vb);
+ sg_init_table(sg, 2);
+
+ hdr.id = cpu_to_virtio32(vb->vdev, BALLOON_GET_FREE_PAGES);
+ hdr.page_shift = cpu_to_virtio32(vb->vdev, PAGE_SHIFT);
+ hdr.start_pfn = cpu_to_virtio64(vb->vdev, 0);
+ hdr.bmap_len = cpu_to_virtio64(vb->vdev, vb->free_bmap_len);
+ sg_set_buf(&sg[0], &hdr, sizeof(hdr));
+ sg_set_buf(&sg[1], vb->free_pages, vb->free_bmap_len);
+ virtqueue_add_outbuf(vq, &sg[0], 2, vb, GFP_KERNEL);
+ break;
default:
break;
}
@@ -689,6 +744,12 @@ static int virtballoon_probe(struct virtio_device *vdev)
err = -ENOMEM;
goto out;
}
+ vb->free_bmap_len = ALIGN(get_max_pfn(), BITS_PER_LONG) / BITS_PER_BYTE;
+ vb->free_pages = kzalloc(vb->free_bmap_len, GFP_KERNEL);
+ if (!vb->free_pages) {
+ err = -ENOMEM;
+ goto out;
+ }
mutex_init(&vb->balloon_lock);
init_waitqueue_head(&vb->acked);
vb->vdev = vdev;
@@ -750,6 +811,7 @@ static void virtballoon_remove(struct virtio_device *vdev)

remove_common(vb);
kfree(vb->page_bitmap);
+ kfree(vb->free_pages);
kfree(vb);
}

--
1.9.1
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