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[209.132.183.28]) by mx.google.com with ESMTPS id m14si47398078qta.354.2019.08.02.13.40.24 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 02 Aug 2019 13:40:24 -0700 (PDT) Received-SPF: pass (google.com: domain of nitesh@redhat.com designates 209.132.183.28 as permitted sender) client-ip=209.132.183.28; Authentication-Results: mx.google.com; spf=pass (google.com: domain of nitesh@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=nitesh@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id E9C2F3090FD0; Fri, 2 Aug 2019 20:40:23 +0000 (UTC) Received: from [10.40.204.149] (ovpn-204-149.brq.redhat.com [10.40.204.149]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 3B1195C207; Fri, 2 Aug 2019 20:40:03 +0000 (UTC) Subject: Re: [PATCH v3 QEMU 2/2] virtio-balloon: Provide a interface for unused page reporting To: Alexander Duyck , kvm@vger.kernel.org, david@redhat.com, mst@redhat.com, dave.hansen@intel.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org Cc: yang.zhang.wz@gmail.com, pagupta@redhat.com, riel@surriel.com, konrad.wilk@oracle.com, willy@infradead.org, lcapitulino@redhat.com, wei.w.wang@intel.com, aarcange@redhat.com, pbonzini@redhat.com, dan.j.williams@intel.com, alexander.h.duyck@linux.intel.com References: <20190801222158.22190.96964.stgit@localhost.localdomain> <20190801224320.24744.16673.stgit@localhost.localdomain> From: Nitesh Narayan Lal Openpgp: preference=signencrypt Autocrypt: addr=nitesh@redhat.com; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190801224320.24744.16673.stgit@localhost.localdomain> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.43]); Fri, 02 Aug 2019 20:40:24 +0000 (UTC) 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 8/1/19 6:43 PM, Alexander Duyck wrote: > From: Alexander Duyck > > Add support for what I am referring to as "unused page reporting". > Basically the idea is to function very similar to how the balloon works= > in that we basically end up madvising the page as not being used. Howev= er > we don't really need to bother with any deflate type logic since the pa= ge > will be faulted back into the guest when it is read or written to. > > This is meant to be a simplification of the existing balloon interface > to use for providing hints to what memory needs to be freed. I am assum= ing > this is safe to do as the deflate logic does not actually appear to do = very > much other than tracking what subpages have been released and which one= s > haven't. > > Signed-off-by: Alexander Duyck > --- > hw/virtio/virtio-balloon.c | 46 +++++++++++++++= +++++++- > include/hw/virtio/virtio-balloon.h | 2 + > include/standard-headers/linux/virtio_balloon.h | 1 + > 3 files changed, 46 insertions(+), 3 deletions(-) > > diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c > index 003b3ebcfdfb..7a30df63bc77 100644 > --- a/hw/virtio/virtio-balloon.c > +++ b/hw/virtio/virtio-balloon.c > @@ -320,6 +320,40 @@ static void balloon_stats_set_poll_interval(Object= *obj, Visitor *v, > balloon_stats_change_timer(s, 0); > } > =20 > +static void virtio_balloon_handle_report(VirtIODevice *vdev, VirtQueue= *vq) > +{ > + VirtIOBalloon *dev =3D VIRTIO_BALLOON(vdev); > + VirtQueueElement *elem; > + > + while ((elem =3D virtqueue_pop(vq, sizeof(VirtQueueElement)))) { > + unsigned int i; > + > + for (i =3D 0; i < elem->in_num; i++) { > + void *addr =3D elem->in_sg[i].iov_base; > + size_t size =3D elem->in_sg[i].iov_len; > + ram_addr_t ram_offset; > + size_t rb_page_size; > + RAMBlock *rb; > + > + if (qemu_balloon_is_inhibited() || dev->poison_val) > + continue; > + > + rb =3D qemu_ram_block_from_host(addr, false, &ram_offset);= > + rb_page_size =3D qemu_ram_pagesize(rb); > + > + /* For now we will simply ignore unaligned memory regions = */ > + if ((ram_offset | size) & (rb_page_size - 1)) > + continue; > + > + ram_block_discard_range(rb, ram_offset, size); > + } > + > + virtqueue_push(vq, elem, 0); > + virtio_notify(vdev, vq); > + g_free(elem); > + } > +} > + > static void virtio_balloon_handle_output(VirtIODevice *vdev, VirtQueue= *vq) > { > VirtIOBalloon *s =3D VIRTIO_BALLOON(vdev); > @@ -627,7 +661,8 @@ static size_t virtio_balloon_config_size(VirtIOBall= oon *s) > return sizeof(struct virtio_balloon_config); > } > if (virtio_has_feature(features, VIRTIO_BALLOON_F_PAGE_POISON) || > - virtio_has_feature(features, VIRTIO_BALLOON_F_FREE_PAGE_HINT))= { > + virtio_has_feature(features, VIRTIO_BALLOON_F_FREE_PAGE_HINT) = || > + virtio_has_feature(features, VIRTIO_BALLOON_F_REPORTING)) { > return sizeof(struct virtio_balloon_config); > } > return offsetof(struct virtio_balloon_config, free_page_report_cmd= _id); > @@ -715,7 +750,8 @@ static uint64_t virtio_balloon_get_features(VirtIOD= evice *vdev, uint64_t f, > VirtIOBalloon *dev =3D VIRTIO_BALLOON(vdev); > f |=3D dev->host_features; > virtio_add_feature(&f, VIRTIO_BALLOON_F_STATS_VQ); > - if (virtio_has_feature(f, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) { > + if (virtio_has_feature(f, VIRTIO_BALLOON_F_FREE_PAGE_HINT) || > + virtio_has_feature(f, VIRTIO_BALLOON_F_REPORTING)) { > virtio_add_feature(&f, VIRTIO_BALLOON_F_PAGE_POISON); > } > =20 > @@ -805,6 +841,10 @@ static void virtio_balloon_device_realize(DeviceSt= ate *dev, Error **errp) > s->dvq =3D virtio_add_queue(vdev, 128, virtio_balloon_handle_outpu= t); > s->svq =3D virtio_add_queue(vdev, 128, virtio_balloon_receive_stat= s); > =20 > + if (virtio_has_feature(s->host_features, VIRTIO_BALLOON_F_REPORTIN= G)) { > + s->rvq =3D virtio_add_queue(vdev, 32, virtio_balloon_handle_re= port); > + } > + This does makes sense. I haven't seen the kernel patch yet, but I am gues= sing you will use this max_vq size to define the capacity. > if (virtio_has_feature(s->host_features, > VIRTIO_BALLOON_F_FREE_PAGE_HINT)) { > s->free_page_vq =3D virtio_add_queue(vdev, VIRTQUEUE_MAX_SIZE,= > @@ -931,6 +971,8 @@ static Property virtio_balloon_properties[] =3D { > */ > DEFINE_PROP_BOOL("qemu-4-0-config-size", VirtIOBalloon, > qemu_4_0_config_size, false), > + DEFINE_PROP_BIT("unused-page-reporting", VirtIOBalloon, host_featu= res, > + VIRTIO_BALLOON_F_REPORTING, true), > DEFINE_PROP_LINK("iothread", VirtIOBalloon, iothread, TYPE_IOTHREA= D, > IOThread *), > DEFINE_PROP_END_OF_LIST(), > diff --git a/include/hw/virtio/virtio-balloon.h b/include/hw/virtio/vir= tio-balloon.h > index 7fe78e5c14d7..db5bf7127112 100644 > --- a/include/hw/virtio/virtio-balloon.h > +++ b/include/hw/virtio/virtio-balloon.h > @@ -42,7 +42,7 @@ enum virtio_balloon_free_page_report_status { > =20 > typedef struct VirtIOBalloon { > VirtIODevice parent_obj; > - VirtQueue *ivq, *dvq, *svq, *free_page_vq; > + VirtQueue *ivq, *dvq, *svq, *free_page_vq, *rvq; > uint32_t free_page_report_status; > uint32_t num_pages; > uint32_t actual; > diff --git a/include/standard-headers/linux/virtio_balloon.h b/include/= standard-headers/linux/virtio_balloon.h > index 9375ca2a70de..1c5f6d6f2de6 100644 > --- a/include/standard-headers/linux/virtio_balloon.h > +++ b/include/standard-headers/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 poisonin= g */ > +#define VIRTIO_BALLOON_F_REPORTING 5 /* Page reporting virtqueue */ Do we really need this change? or is this something which is picked from = the Linux kernel? If we do need it, then Cornelia suggested to split off any update to this= header into a separate patch, so that it can be replaced by a proper headers upd= ate when it is merged. > =20 > /* Size of a PFN in the balloon interface. */ > #define VIRTIO_BALLOON_PFN_SHIFT 12 > --=20 Thanks Nitesh