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Message-ID: <fc99b28d-2efd-cd05-59e4-99f35bd37cac@redhat.com>
Date: Thu, 25 Jul 2019 13:42:41 -0400
From: Nitesh Narayan Lal <nitesh@...hat.com>
To: Alexander Duyck <alexander.duyck@...il.com>, kvm@...r.kernel.org,
david@...hat.com, mst@...hat.com, dave.hansen@...el.com,
linux-kernel@...r.kernel.org, linux-mm@...ck.org,
akpm@...ux-foundation.org
Cc: yang.zhang.wz@...il.com, pagupta@...hat.com, riel@...riel.com,
konrad.wilk@...cle.com, lcapitulino@...hat.com,
wei.w.wang@...el.com, aarcange@...hat.com, pbonzini@...hat.com,
dan.j.williams@...el.com, alexander.h.duyck@...ux.intel.com
Subject: Re: [PATCH v2 5/5] virtio-balloon: Add support for providing page
hints to host
On 7/24/19 1:05 PM, Alexander Duyck wrote:
> From: Alexander Duyck <alexander.h.duyck@...ux.intel.com>
>
> Add support for the page hinting feature provided by virtio-balloon.
> Hinting differs from the regular balloon functionality in that is is
> much less durable than a standard memory balloon. Instead of creating a
> list of pages that cannot be accessed the pages are only inaccessible
> while they are being indicated to the virtio interface. Once the
> interface has acknowledged them they are placed back into their respective
> free lists and are once again accessible by the guest system.
>
> Signed-off-by: Alexander Duyck <alexander.h.duyck@...ux.intel.com>
> ---
> drivers/virtio/Kconfig | 1 +
> drivers/virtio/virtio_balloon.c | 47 +++++++++++++++++++++++++++++++++++
> include/uapi/linux/virtio_balloon.h | 1 +
> 3 files changed, 49 insertions(+)
>
> diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig
> index 078615cf2afc..d45556ae1f81 100644
> --- a/drivers/virtio/Kconfig
> +++ b/drivers/virtio/Kconfig
> @@ -58,6 +58,7 @@ 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 226fbb995fb0..dee9f8f3ad09 100644
> --- a/drivers/virtio/virtio_balloon.c
> +++ b/drivers/virtio/virtio_balloon.c
> @@ -19,6 +19,7 @@
> #include <linux/mount.h>
> #include <linux/magic.h>
> #include <linux/pseudo_fs.h>
> +#include <linux/page_hinting.h>
>
> /*
> * Balloon device works in 4K page units. So each page is pointed to by
> @@ -27,6 +28,7 @@
> */
> #define VIRTIO_BALLOON_PAGES_PER_PAGE (unsigned)(PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT)
> #define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256
> +#define VIRTIO_BALLOON_ARRAY_HINTS_MAX 32
> #define VIRTBALLOON_OOM_NOTIFY_PRIORITY 80
>
> #define VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG (__GFP_NORETRY | __GFP_NOWARN | \
> @@ -46,6 +48,7 @@ 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
> };
>
> @@ -113,6 +116,10 @@ struct virtio_balloon {
>
> /* To register a shrinker to shrink memory upon memory pressure */
> struct shrinker shrinker;
> +
> + /* Unused page hinting device */
> + struct virtqueue *hinting_vq;
> + struct page_hinting_dev_info ph_dev_info;
> };
>
> static struct virtio_device_id id_table[] = {
> @@ -152,6 +159,22 @@ static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
>
> }
>
> +void virtballoon_page_hinting_react(struct page_hinting_dev_info *ph_dev_info,
> + unsigned int num_hints)
> +{
> + struct virtio_balloon *vb =
> + container_of(ph_dev_info, struct virtio_balloon, ph_dev_info);
> + struct virtqueue *vq = vb->hinting_vq;
> + unsigned int unused;
> +
> + /* We should always be able to add these buffers to an empty queue. */
> + virtqueue_add_inbuf(vq, ph_dev_info->sg, num_hints, vb, GFP_KERNEL);
> + virtqueue_kick(vq);
> +
> + /* When host has read buffer, this completes via balloon_ack */
> + wait_event(vb->acked, virtqueue_get_buf(vq, &unused));
> +}
> +
> static void set_page_pfns(struct virtio_balloon *vb,
> __virtio32 pfns[], struct page *page)
> {
> @@ -476,6 +499,7 @@ 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";
> @@ -487,11 +511,19 @@ 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)) {
> @@ -924,12 +956,24 @@ static int virtballoon_probe(struct virtio_device *vdev)
> if (err)
> goto out_del_balloon_wq;
> }
> +
> + vb->ph_dev_info.react = virtballoon_page_hinting_react;
> + vb->ph_dev_info.capacity = VIRTIO_BALLOON_ARRAY_HINTS_MAX;
> + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_HINTING)) {
> + err = page_hinting_startup(&vb->ph_dev_info);
> + if (err)
> + goto out_unregister_shrinker;
> + }
Any reason why you have kept vb->ph_dev_info.react & vb->ph_dev_info.capacity
initialization outside the feature check?
> +
> virtio_device_ready(vdev);
>
> if (towards_target(vb))
> virtballoon_changed(vdev);
> return 0;
>
> +out_unregister_shrinker:
> + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
> + virtio_balloon_unregister_shrinker(vb);
> out_del_balloon_wq:
> if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
> destroy_workqueue(vb->balloon_wq);
> @@ -958,6 +1002,8 @@ static void virtballoon_remove(struct virtio_device *vdev)
> {
> struct virtio_balloon *vb = vdev->priv;
>
> + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_HINTING))
> + page_hinting_shutdown(&vb->ph_dev_info);
> if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
> virtio_balloon_unregister_shrinker(vb);
> spin_lock_irq(&vb->stop_update_lock);
> @@ -1027,6 +1073,7 @@ static int virtballoon_validate(struct virtio_device *vdev)
> VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
> 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..2b0f62814e22 100644
> --- a/include/uapi/linux/virtio_balloon.h
> +++ b/include/uapi/linux/virtio_balloon.h
> @@ -36,6 +36,7 @@
> #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 */
> +#define VIRTIO_BALLOON_F_HINTING 5 /* Page hinting virtqueue */
>
> /* Size of a PFN in the balloon interface. */
> #define VIRTIO_BALLOON_PFN_SHIFT 12
>
--
Thanks
Nitesh
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