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[79.181.48.215]) by smtp.gmail.com with ESMTPSA id c20sm3186746qtc.13.2019.12.12.23.08.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 12 Dec 2019 23:08:27 -0800 (PST) Date: Fri, 13 Dec 2019 02:08:19 -0500 From: "Michael S. Tsirkin" To: Alexander Duyck Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, willy@infradead.org, mhocko@kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, mgorman@techsingularity.net, vbabka@suse.cz, yang.zhang.wz@gmail.com, nitesh@redhat.com, konrad.wilk@oracle.com, david@redhat.com, pagupta@redhat.com, riel@surriel.com, lcapitulino@redhat.com, dave.hansen@intel.com, wei.w.wang@intel.com, aarcange@redhat.com, pbonzini@redhat.com, dan.j.williams@intel.com, alexander.h.duyck@linux.intel.com, osalvador@suse.de Subject: Re: [PATCH v15 6/7] virtio-balloon: Add support for providing free page reports to host Message-ID: <20191213020553-mutt-send-email-mst@kernel.org> References: <20191205161928.19548.41654.stgit@localhost.localdomain> <20191205162255.19548.63866.stgit@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191205162255.19548.63866.stgit@localhost.localdomain> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Dec 05, 2019 at 08:22:55AM -0800, Alexander Duyck wrote: > From: Alexander Duyck > > Add support for the page reporting feature provided by virtio-balloon. > Reporting 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. > > Unlike a standard balloon we don't inflate and deflate the pages. Instead > we perform the reporting, and once the reporting is completed it is > assumed that the page has been dropped from the guest and will be faulted > back in the next time the page is accessed. > > For this reason when I had originally introduced the patch set I referred > to this behavior as a "bubble" instead of a "balloon" since the duration > is short lived, and when the page is touched the "bubble" is popped and > the page is faulted back in. > > Signed-off-by: Alexander Duyck virtio POV is fine here: Acked-by: Michael S. Tsirkin However please copy virtio-comment on UAPI changes. If possible isolate the last chunk in a patch by itself to make it easier for non-kernel developers to review. > --- > drivers/virtio/Kconfig | 1 + > drivers/virtio/virtio_balloon.c | 64 +++++++++++++++++++++++++++++++++++ > include/uapi/linux/virtio_balloon.h | 1 + > 3 files changed, 66 insertions(+) > > diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig > index 078615cf2afc..4b2dd8259ff5 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_REPORTING > ---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 252591bc7e01..ecd54edba968 100644 > --- a/drivers/virtio/virtio_balloon.c > +++ b/drivers/virtio/virtio_balloon.c > @@ -19,6 +19,7 @@ > #include > #include > #include > +#include > > /* > * Balloon device works in 4K page units. So each page is pointed to by > @@ -47,6 +48,7 @@ enum virtio_balloon_vq { > VIRTIO_BALLOON_VQ_DEFLATE, > VIRTIO_BALLOON_VQ_STATS, > VIRTIO_BALLOON_VQ_FREE_PAGE, > + VIRTIO_BALLOON_VQ_REPORTING, > VIRTIO_BALLOON_VQ_MAX > }; > > @@ -114,6 +116,10 @@ struct virtio_balloon { > > /* To register a shrinker to shrink memory upon memory pressure */ > struct shrinker shrinker; > + > + /* Free page reporting device */ > + struct virtqueue *reporting_vq; > + struct page_reporting_dev_info pr_dev_info; > }; > > static struct virtio_device_id id_table[] = { > @@ -153,6 +159,33 @@ static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq) > > } > > +int virtballoon_free_page_report(struct page_reporting_dev_info *pr_dev_info, > + struct scatterlist *sg, unsigned int nents) > +{ > + struct virtio_balloon *vb = > + container_of(pr_dev_info, struct virtio_balloon, pr_dev_info); > + struct virtqueue *vq = vb->reporting_vq; > + unsigned int unused, err; > + > + /* We should always be able to add these buffers to an empty queue. */ > + err = virtqueue_add_inbuf(vq, sg, nents, vb, GFP_NOWAIT | __GFP_NOWARN); > + > + /* > + * In the extremely unlikely case that something has occurred and we > + * are able to trigger an error we will simply display a warning > + * and exit without actually processing the pages. > + */ > + if (WARN_ON_ONCE(err)) > + return err; > + > + virtqueue_kick(vq); > + > + /* When host has read buffer, this completes via balloon_ack */ > + wait_event(vb->acked, virtqueue_get_buf(vq, &unused)); > + > + return 0; > +} > + > static void set_page_pfns(struct virtio_balloon *vb, > __virtio32 pfns[], struct page *page) > { > @@ -477,6 +510,7 @@ 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_REPORTING] = NULL; > > if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) { > names[VIRTIO_BALLOON_VQ_STATS] = "stats"; > @@ -488,6 +522,11 @@ static int init_vqs(struct virtio_balloon *vb) > callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL; > } > > + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) { > + names[VIRTIO_BALLOON_VQ_REPORTING] = "reporting_vq"; > + callbacks[VIRTIO_BALLOON_VQ_REPORTING] = balloon_ack; > + } > + > err = vb->vdev->config->find_vqs(vb->vdev, VIRTIO_BALLOON_VQ_MAX, > vqs, callbacks, names, NULL, NULL); > if (err) > @@ -520,6 +559,9 @@ static int init_vqs(struct virtio_balloon *vb) > if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) > vb->free_page_vq = vqs[VIRTIO_BALLOON_VQ_FREE_PAGE]; > > + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) > + vb->reporting_vq = vqs[VIRTIO_BALLOON_VQ_REPORTING]; > + > return 0; > } > > @@ -939,12 +981,31 @@ static int virtballoon_probe(struct virtio_device *vdev) > if (err) > goto out_del_balloon_wq; > } > + > + vb->pr_dev_info.report = virtballoon_free_page_report; > + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) { > + unsigned int capacity; > + > + capacity = virtqueue_get_vring_size(vb->reporting_vq); > + if (capacity < PAGE_REPORTING_CAPACITY) { > + err = -ENOSPC; > + goto out_unregister_shrinker; > + } > + > + err = page_reporting_register(&vb->pr_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); > @@ -973,6 +1034,8 @@ static void virtballoon_remove(struct virtio_device *vdev) > { > struct virtio_balloon *vb = vdev->priv; > > + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) > + page_reporting_unregister(&vb->pr_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); > @@ -1045,6 +1108,7 @@ 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_REPORTING, > }; > > 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..19974392d324 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_REPORTING 5 /* Page reporting virtqueue */ > > /* Size of a PFN in the balloon interface. */ > #define VIRTIO_BALLOON_PFN_SHIFT 12