On Wed, Jun 19, 2019 at 03:33:38PM -0700, Alexander Duyck wrote: > From: Alexander Duyck <[email protected]> > > Add support for aerating memory using the 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 <[email protected]> > --- > drivers/virtio/Kconfig | 1 > drivers/virtio/virtio_balloon.c | 110 > ++++++++++++++++++++++++++++++++++- > include/uapi/linux/virtio_balloon.h | 1 > 3 files changed, 108 insertions(+), 4 deletions(-) > > diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig > index 023fc3bc01c6..9cdaccf92c3a 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 AERATION > ---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..91f1e8c9017d 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/memory_aeration.h> > > /* > * Balloon device works in 4K page units. So each page is pointed to by > @@ -26,6 +27,7 @@ > */ > #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 | \ > @@ -45,6 +47,7 @@ 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 +57,8 @@ 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; > @@ -103,9 +107,21 @@ struct virtio_balloon { > /* Synchronize access/update to this struct virtio_balloon elements */ > struct mutex balloon_lock; > > - /* The array of pfns we tell the Host about. */ > - unsigned int num_pfns; > - __virtio32 pfns[VIRTIO_BALLOON_ARRAY_PFNS_MAX]; > + > + union { > + /* The array of pfns we tell the Host about. */ > + struct { > + unsigned int num_pfns; > + __virtio32 pfns[VIRTIO_BALLOON_ARRAY_PFNS_MAX]; > + }; > + /* The array of physical addresses we are hinting on */ > + struct { > + unsigned int num_hints; > + __virtio64 hints[VIRTIO_BALLOON_ARRAY_HINTS_MAX]; > + }; > + }; > + > + struct aerator_dev_info a_dev_info; > > /* Memory statistics */ > struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR]; > @@ -151,6 +167,68 @@ static void tell_host(struct virtio_balloon *vb, struct > virtqueue *vq) > > } > > +static u64 page_to_hints_pa_order(struct page *page) > +{ > + unsigned char order; > + dma_addr_t pa; > + > + BUILD_BUG_ON((64 - VIRTIO_BALLOON_PFN_SHIFT) >= > + (1 << VIRTIO_BALLOON_PFN_SHIFT)); > + > + /* > + * Record physical page address combined with page order. > + * Order will never exceed 64 - VIRTIO_BALLON_PFN_SHIFT > + * since the size has to fit into a 64b value. So as long > + * as VIRTIO_BALLOON_SHIFT is greater than this combining > + * the two values should be safe. > + */ > + pa = page_to_phys(page); > + order = page_private(page) + > + PAGE_SHIFT - VIRTIO_BALLOON_PFN_SHIFT; > + > + return (u64)(pa | order); > +} > + > +void virtballoon_aerator_react(struct aerator_dev_info *a_dev_info) > +{ > + struct virtio_balloon *vb = container_of(a_dev_info, > + struct virtio_balloon, > + a_dev_info); > + struct virtqueue *vq = vb->hinting_vq; > + struct scatterlist sg; > + unsigned int unused; > + struct page *page; > + > + mutex_lock(&vb->balloon_lock); > + > + vb->num_hints = 0; > + > + list_for_each_entry(page, &a_dev_info->batch, lru) { > + vb->hints[vb->num_hints++] = > + cpu_to_virtio64(vb->vdev, > + page_to_hints_pa_order(page)); > + } > + > + /* We shouldn't have been called if there is nothing to process */ > + if (WARN_ON(vb->num_hints == 0)) > + goto out; > + > + sg_init_one(&sg, vb->hints, > + sizeof(vb->hints[0]) * vb->num_hints); > + > + /* > + * We should always be able to add one buffer to an > + * empty queue. > + */ > + virtqueue_add_outbuf(vq, &sg, 1, 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)); > +out: > + mutex_unlock(&vb->balloon_lock); > +} > + > static void set_page_pfns(struct virtio_balloon *vb, > __virtio32 pfns[], struct page *page) > { > @@ -475,6 +553,7 @@ 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 +565,19 @@ 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)) { > @@ -929,12 +1016,24 @@ static int virtballoon_probe(struct virtio_device > *vdev) > if (err) > goto out_del_balloon_wq; > } > + > + vb->a_dev_info.react = virtballoon_aerator_react; > + vb->a_dev_info.capacity = VIRTIO_BALLOON_ARRAY_HINTS_MAX; > + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_HINTING)) { > + err = aerator_startup(&vb->a_dev_info); > + if (err) > + goto out_unregister_shrinker; > + } > + > 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); > @@ -963,6 +1062,8 @@ static void virtballoon_remove(struct virtio_device > *vdev) > { > struct virtio_balloon *vb = vdev->priv; > > + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_HINTING)) > + aerator_shutdown(); > if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) > virtio_balloon_unregister_shrinker(vb); > spin_lock_irq(&vb->stop_update_lock); > @@ -1032,6 +1133,7 @@ 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
The approach here is very close to what on-demand hinting that is already upstream does. This should have resulted in a most of the code being shared but this does not seem to happen here. Can we unify the code in some way? It can still use a separate feature flag, but there are things I like very much about current hinting code, such as using s/g instead of passing PFNs in a buffer. If this doesn't work could you elaborate on why? -- MST
