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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 In-Reply-To: <20191205162255.19548.63866.stgit@localhost.localdomain> X-MC-Unique: vxO1hDo8O7W7DZ5IpXXt6Q-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Content-Disposition: inline X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Dec 05, 2019 at 08:22:55AM -0800, Alexander Duyck wrote: > From: Alexander Duyck >=20 > 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 respectiv= e > free lists and are once again accessible by the guest system. >=20 > 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. >=20 > 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. >=20 > 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(+) >=20 > 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 > =09tristate "Virtio balloon driver" > =09depends on VIRTIO > =09select MEMORY_BALLOON > +=09select PAGE_REPORTING > =09---help--- > =09 This driver supports increasing and decreasing the amount > =09 of memory within a KVM guest. > diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_ball= oon.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 > =20 > /* > * Balloon device works in 4K page units. So each page is pointed to by > @@ -47,6 +48,7 @@ enum virtio_balloon_vq { > =09VIRTIO_BALLOON_VQ_DEFLATE, > =09VIRTIO_BALLOON_VQ_STATS, > =09VIRTIO_BALLOON_VQ_FREE_PAGE, > +=09VIRTIO_BALLOON_VQ_REPORTING, > =09VIRTIO_BALLOON_VQ_MAX > }; > =20 > @@ -114,6 +116,10 @@ struct virtio_balloon { > =20 > =09/* To register a shrinker to shrink memory upon memory pressure */ > =09struct shrinker shrinker; > + > +=09/* Free page reporting device */ > +=09struct virtqueue *reporting_vq; > +=09struct page_reporting_dev_info pr_dev_info; > }; > =20 > static struct virtio_device_id id_table[] =3D { > @@ -153,6 +159,33 @@ static void tell_host(struct virtio_balloon *vb, str= uct virtqueue *vq) > =20 > } > =20 > +int virtballoon_free_page_report(struct page_reporting_dev_info *pr_dev_= info, > +=09=09=09=09 struct scatterlist *sg, unsigned int nents) > +{ > +=09struct virtio_balloon *vb =3D > +=09=09container_of(pr_dev_info, struct virtio_balloon, pr_dev_info); > +=09struct virtqueue *vq =3D vb->reporting_vq; > +=09unsigned int unused, err; > + > +=09/* We should always be able to add these buffers to an empty queue. *= / > +=09err =3D virtqueue_add_inbuf(vq, sg, nents, vb, GFP_NOWAIT | __GFP_NOW= ARN); > + > +=09/* > +=09 * In the extremely unlikely case that something has occurred and we > +=09 * are able to trigger an error we will simply display a warning > +=09 * and exit without actually processing the pages. > +=09 */ > +=09if (WARN_ON_ONCE(err)) > +=09=09return err; > + > +=09virtqueue_kick(vq); > + > +=09/* When host has read buffer, this completes via balloon_ack */ > +=09wait_event(vb->acked, virtqueue_get_buf(vq, &unused)); > + > +=09return 0; > +} > + > static void set_page_pfns(struct virtio_balloon *vb, > =09=09=09 __virtio32 pfns[], struct page *page) > { > @@ -477,6 +510,7 @@ static int init_vqs(struct virtio_balloon *vb) > =09names[VIRTIO_BALLOON_VQ_DEFLATE] =3D "deflate"; > =09names[VIRTIO_BALLOON_VQ_STATS] =3D NULL; > =09names[VIRTIO_BALLOON_VQ_FREE_PAGE] =3D NULL; > +=09names[VIRTIO_BALLOON_VQ_REPORTING] =3D NULL; > =20 > =09if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) { > =09=09names[VIRTIO_BALLOON_VQ_STATS] =3D "stats"; > @@ -488,6 +522,11 @@ static int init_vqs(struct virtio_balloon *vb) > =09=09callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] =3D NULL; > =09} > =20 > +=09if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) { > +=09=09names[VIRTIO_BALLOON_VQ_REPORTING] =3D "reporting_vq"; > +=09=09callbacks[VIRTIO_BALLOON_VQ_REPORTING] =3D balloon_ack; > +=09} > + > =09err =3D vb->vdev->config->find_vqs(vb->vdev, VIRTIO_BALLOON_VQ_MAX, > =09=09=09=09=09 vqs, callbacks, names, NULL, NULL); > =09if (err) > @@ -520,6 +559,9 @@ static int init_vqs(struct virtio_balloon *vb) > =09if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) > =09=09vb->free_page_vq =3D vqs[VIRTIO_BALLOON_VQ_FREE_PAGE]; > =20 > +=09if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) > +=09=09vb->reporting_vq =3D vqs[VIRTIO_BALLOON_VQ_REPORTING]; > + > =09return 0; > } > =20 > @@ -939,12 +981,31 @@ static int virtballoon_probe(struct virtio_device *= vdev) > =09=09if (err) > =09=09=09goto out_del_balloon_wq; > =09} > + > +=09vb->pr_dev_info.report =3D virtballoon_free_page_report; > +=09if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) { > +=09=09unsigned int capacity; > + > +=09=09capacity =3D virtqueue_get_vring_size(vb->reporting_vq); > +=09=09if (capacity < PAGE_REPORTING_CAPACITY) { > +=09=09=09err =3D -ENOSPC; > +=09=09=09goto out_unregister_shrinker; > +=09=09} > + > +=09=09err =3D page_reporting_register(&vb->pr_dev_info); > +=09=09if (err) > +=09=09=09goto out_unregister_shrinker; > +=09} > + > =09virtio_device_ready(vdev); > =20 > =09if (towards_target(vb)) > =09=09virtballoon_changed(vdev); > =09return 0; > =20 > +out_unregister_shrinker: > +=09if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) > +=09=09virtio_balloon_unregister_shrinker(vb); > out_del_balloon_wq: > =09if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) > =09=09destroy_workqueue(vb->balloon_wq); > @@ -973,6 +1034,8 @@ static void virtballoon_remove(struct virtio_device = *vdev) > { > =09struct virtio_balloon *vb =3D vdev->priv; > =20 > +=09if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) > +=09=09page_reporting_unregister(&vb->pr_dev_info); > =09if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) > =09=09virtio_balloon_unregister_shrinker(vb); > =09spin_lock_irq(&vb->stop_update_lock); > @@ -1045,6 +1108,7 @@ static int virtballoon_validate(struct virtio_devic= e *vdev) > =09VIRTIO_BALLOON_F_DEFLATE_ON_OOM, > =09VIRTIO_BALLOON_F_FREE_PAGE_HINT, > =09VIRTIO_BALLOON_F_PAGE_POISON, > +=09VIRTIO_BALLOON_F_REPORTING, > }; > =20 > static struct virtio_driver virtio_balloon_driver =3D { > diff --git a/include/uapi/linux/virtio_balloon.h b/include/uapi/linux/vir= tio_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=092 /* Deflate balloon on OOM */ > #define VIRTIO_BALLOON_F_FREE_PAGE_HINT=093 /* VQ to report free pages *= / > #define VIRTIO_BALLOON_F_PAGE_POISON=094 /* Guest is using page poisonin= g */ > +#define VIRTIO_BALLOON_F_REPORTING=095 /* Page reporting virtqueue */ > =20 > /* Size of a PFN in the balloon interface. */ > #define VIRTIO_BALLOON_PFN_SHIFT 12