[RFC][Patch v11 2/2] virtio-balloon: page_hinting: reporting to the host
From: Nitesh Narayan Lal
Date: Wed Jul 10 2019 - 15:52:36 EST
Enables the kernel to negotiate VIRTIO_BALLOON_F_HINTING feature with the
host. If it is available and page_hinting_flag is set to true, page_hinting
is enabled and its callbacks are configured along with the max_pages count
which indicates the maximum number of pages that can be isolated and hinted
at a time. Currently, only free pages of order >= (MAX_ORDER - 2) are
reported. To prevent any false OOM max_pages count is set to 16.
By default page_hinting feature is enabled and gets loaded as soon
as the virtio-balloon driver is loaded. However, it could be disabled
by writing the page_hinting_flag which is a virtio-balloon parameter.
Signed-off-by: Nitesh Narayan Lal <nitesh@xxxxxxxxxx>
---
drivers/virtio/Kconfig | 1 +
drivers/virtio/virtio_balloon.c | 91 ++++++++++++++++++++++++++++-
include/uapi/linux/virtio_balloon.h | 11 ++++
3 files changed, 102 insertions(+), 1 deletion(-)
diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig
index 023fc3bc01c6..dcc0cb4269a5 100644
--- a/drivers/virtio/Kconfig
+++ b/drivers/virtio/Kconfig
@@ -47,6 +47,7 @@ config VIRTIO_BALLOON
tristate "Virtio balloon driver"
depends on VIRTIO
select MEMORY_BALLOON
+ select PAGE_HINTING
---help---
This driver supports increasing and decreasing the amount
of memory within a KVM guest.
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 44339fc87cc7..1fb0eb0b2c20 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -18,6 +18,7 @@
#include <linux/mm.h>
#include <linux/mount.h>
#include <linux/magic.h>
+#include <linux/page_hinting.h>
/*
* Balloon device works in 4K page units. So each page is pointed to by
@@ -35,6 +36,12 @@
/* The size of a free page block in bytes */
#define VIRTIO_BALLOON_FREE_PAGE_SIZE \
(1 << (VIRTIO_BALLOON_FREE_PAGE_ORDER + PAGE_SHIFT))
+/* Number of isolated pages to be reported to the host at a time.
+ * TODO:
+ * 1. Set it via host.
+ * 2. Find an optimal value for this.
+ */
+#define PAGE_HINTING_MAX_PAGES 16
#ifdef CONFIG_BALLOON_COMPACTION
static struct vfsmount *balloon_mnt;
@@ -45,6 +52,7 @@ enum virtio_balloon_vq {
VIRTIO_BALLOON_VQ_DEFLATE,
VIRTIO_BALLOON_VQ_STATS,
VIRTIO_BALLOON_VQ_FREE_PAGE,
+ VIRTIO_BALLOON_VQ_HINTING,
VIRTIO_BALLOON_VQ_MAX
};
@@ -54,7 +62,8 @@ enum virtio_balloon_config_read {
struct virtio_balloon {
struct virtio_device *vdev;
- struct virtqueue *inflate_vq, *deflate_vq, *stats_vq, *free_page_vq;
+ struct virtqueue *inflate_vq, *deflate_vq, *stats_vq, *free_page_vq,
+ *hinting_vq;
/* Balloon's own wq for cpu-intensive work items */
struct workqueue_struct *balloon_wq;
@@ -112,6 +121,9 @@ struct virtio_balloon {
/* To register a shrinker to shrink memory upon memory pressure */
struct shrinker shrinker;
+
+ /* Array object pointing at the isolated pages ready for hinting */
+ struct isolated_memory isolated_pages[PAGE_HINTING_MAX_PAGES];
};
static struct virtio_device_id id_table[] = {
@@ -119,6 +131,66 @@ static struct virtio_device_id id_table[] = {
{ 0 },
};
+static struct page_hinting_config page_hinting_conf;
+bool page_hinting_flag = true;
+struct virtio_balloon *hvb;
+module_param(page_hinting_flag, bool, 0444);
+MODULE_PARM_DESC(page_hinting_flag, "Enable page hinting");
+
+static int page_hinting_report(void)
+{
+ struct virtqueue *vq = hvb->hinting_vq;
+ struct scatterlist sg;
+ int err = 0, unused;
+
+ mutex_lock(&hvb->balloon_lock);
+ sg_init_one(&sg, hvb->isolated_pages, sizeof(hvb->isolated_pages[0]) *
+ PAGE_HINTING_MAX_PAGES);
+ err = virtqueue_add_outbuf(vq, &sg, 1, hvb, GFP_KERNEL);
+ if (!err)
+ virtqueue_kick(hvb->hinting_vq);
+ wait_event(hvb->acked, virtqueue_get_buf(vq, &unused));
+ mutex_unlock(&hvb->balloon_lock);
+ return err;
+}
+
+void hint_pages(struct list_head *pages)
+{
+ struct device *dev = &hvb->vdev->dev;
+ struct page *page, *next;
+ int idx = 0, order, err;
+ unsigned long pfn;
+
+ list_for_each_entry_safe(page, next, pages, lru) {
+ pfn = page_to_pfn(page);
+ order = page_private(page);
+ hvb->isolated_pages[idx].phys_addr = pfn << PAGE_SHIFT;
+ hvb->isolated_pages[idx].size = (1 << order) * PAGE_SIZE;
+ idx++;
+ }
+ err = page_hinting_report();
+ if (err < 0)
+ dev_err(dev, "Failed to hint pages, err = %d\n", err);
+}
+
+static void page_hinting_init(struct virtio_balloon *vb)
+{
+ struct device *dev = &vb->vdev->dev;
+ int err;
+
+ page_hinting_conf.hint_pages = hint_pages;
+ page_hinting_conf.max_pages = PAGE_HINTING_MAX_PAGES;
+ err = page_hinting_enable(&page_hinting_conf);
+ if (err < 0) {
+ dev_err(dev, "Failed to enable page-hinting, err = %d\n", err);
+ page_hinting_flag = false;
+ page_hinting_conf.hint_pages = NULL;
+ page_hinting_conf.max_pages = 0;
+ return;
+ }
+ hvb = vb;
+}
+
static u32 page_to_balloon_pfn(struct page *page)
{
unsigned long pfn = page_to_pfn(page);
@@ -475,6 +547,7 @@ static int init_vqs(struct virtio_balloon *vb)
names[VIRTIO_BALLOON_VQ_DEFLATE] = "deflate";
names[VIRTIO_BALLOON_VQ_STATS] = NULL;
names[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
+ names[VIRTIO_BALLOON_VQ_HINTING] = NULL;
if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
names[VIRTIO_BALLOON_VQ_STATS] = "stats";
@@ -486,11 +559,18 @@ static int init_vqs(struct virtio_balloon *vb)
callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
}
+ if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_HINTING)) {
+ names[VIRTIO_BALLOON_VQ_HINTING] = "hinting_vq";
+ callbacks[VIRTIO_BALLOON_VQ_HINTING] = balloon_ack;
+ }
err = vb->vdev->config->find_vqs(vb->vdev, VIRTIO_BALLOON_VQ_MAX,
vqs, callbacks, names, NULL, NULL);
if (err)
return err;
+ if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_HINTING))
+ vb->hinting_vq = vqs[VIRTIO_BALLOON_VQ_HINTING];
+
vb->inflate_vq = vqs[VIRTIO_BALLOON_VQ_INFLATE];
vb->deflate_vq = vqs[VIRTIO_BALLOON_VQ_DEFLATE];
if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
@@ -929,6 +1009,9 @@ static int virtballoon_probe(struct virtio_device *vdev)
if (err)
goto out_del_balloon_wq;
}
+ if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_HINTING) &&
+ page_hinting_flag)
+ page_hinting_init(vb);
virtio_device_ready(vdev);
if (towards_target(vb))
@@ -976,6 +1059,10 @@ static void virtballoon_remove(struct virtio_device *vdev)
destroy_workqueue(vb->balloon_wq);
}
+ if (!page_hinting_flag) {
+ hvb = NULL;
+ page_hinting_disable();
+ }
remove_common(vb);
#ifdef CONFIG_BALLOON_COMPACTION
if (vb->vb_dev_info.inode)
@@ -1030,8 +1117,10 @@ static unsigned int features[] = {
VIRTIO_BALLOON_F_MUST_TELL_HOST,
VIRTIO_BALLOON_F_STATS_VQ,
VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
+ VIRTIO_BALLOON_F_HINTING,
VIRTIO_BALLOON_F_FREE_PAGE_HINT,
VIRTIO_BALLOON_F_PAGE_POISON,
+ VIRTIO_BALLOON_F_HINTING,
};
static struct virtio_driver virtio_balloon_driver = {
diff --git a/include/uapi/linux/virtio_balloon.h b/include/uapi/linux/virtio_balloon.h
index a1966cd7b677..29eed0ec83d3 100644
--- a/include/uapi/linux/virtio_balloon.h
+++ b/include/uapi/linux/virtio_balloon.h
@@ -36,6 +36,8 @@
#define VIRTIO_BALLOON_F_DEFLATE_ON_OOM 2 /* Deflate balloon on OOM */
#define VIRTIO_BALLOON_F_FREE_PAGE_HINT 3 /* VQ to report free pages */
#define VIRTIO_BALLOON_F_PAGE_POISON 4 /* Guest is using page poisoning */
+/* TODO: Find a better name to avoid any confusion with FREE_PAGE_HINT */
+#define VIRTIO_BALLOON_F_HINTING 5 /* Page hinting virtqueue */
/* Size of a PFN in the balloon interface. */
#define VIRTIO_BALLOON_PFN_SHIFT 12
@@ -108,4 +110,13 @@ struct virtio_balloon_stat {
__virtio64 val;
} __attribute__((packed));
+/*
+ * struct isolated_memory- holds the pages which will be reported to the host.
+ * @phys_add: physical address associated with a page.
+ * @size: total size of memory to be reported.
+ */
+struct isolated_memory {
+ __virtio64 phys_addr;
+ __virtio64 size;
+};
#endif /* _LINUX_VIRTIO_BALLOON_H */
--
2.21.0