From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id F09D3C7618F for ; Wed, 24 Jul 2019 19:07:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BE57E218F0 for ; Wed, 24 Jul 2019 19:07:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728867AbfGXTHv (ORCPT ); Wed, 24 Jul 2019 15:07:51 -0400 Received: from mx1.redhat.com ([209.132.183.28]:39290 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726622AbfGXTHu (ORCPT ); Wed, 24 Jul 2019 15:07:50 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id A85DA81F2F; Wed, 24 Jul 2019 19:07:49 +0000 (UTC) Received: from [10.18.17.163] (dhcp-17-163.bos.redhat.com [10.18.17.163]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 385AC5D71C; Wed, 24 Jul 2019 19:07:43 +0000 (UTC) Subject: Re: [PATCH v2 5/5] virtio-balloon: Add support for providing page hints to host To: "Michael S. Tsirkin" , Alexander Duyck Cc: kvm@vger.kernel.org, david@redhat.com, dave.hansen@intel.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, yang.zhang.wz@gmail.com, pagupta@redhat.com, riel@surriel.com, konrad.wilk@oracle.com, 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: <20190724165158.6685.87228.stgit@localhost.localdomain> <20190724170514.6685.17161.stgit@localhost.localdomain> <20190724143902-mutt-send-email-mst@kernel.org> From: Nitesh Narayan Lal Openpgp: preference=signencrypt Autocrypt: addr=nitesh@redhat.com; prefer-encrypt=mutual; keydata= mQINBFl4pQoBEADT/nXR2JOfsCjDgYmE2qonSGjkM1g8S6p9UWD+bf7YEAYYYzZsLtbilFTe z4nL4AV6VJmC7dBIlTi3Mj2eymD/2dkKP6UXlliWkq67feVg1KG+4UIp89lFW7v5Y8Muw3Fm uQbFvxyhN8n3tmhRe+ScWsndSBDxYOZgkbCSIfNPdZrHcnOLfA7xMJZeRCjqUpwhIjxQdFA7 n0s0KZ2cHIsemtBM8b2WXSQG9CjqAJHVkDhrBWKThDRF7k80oiJdEQlTEiVhaEDURXq+2XmG jpCnvRQDb28EJSsQlNEAzwzHMeplddfB0vCg9fRk/kOBMDBtGsTvNT9OYUZD+7jaf0gvBvBB lbKmmMMX7uJB+ejY7bnw6ePNrVPErWyfHzR5WYrIFUtgoR3LigKnw5apzc7UIV9G8uiIcZEn C+QJCK43jgnkPcSmwVPztcrkbC84g1K5v2Dxh9amXKLBA1/i+CAY8JWMTepsFohIFMXNLj+B RJoOcR4HGYXZ6CAJa3Glu3mCmYqHTOKwezJTAvmsCLd3W7WxOGF8BbBjVaPjcZfavOvkin0u DaFvhAmrzN6lL0msY17JCZo046z8oAqkyvEflFbC0S1R/POzehKrzQ1RFRD3/YzzlhmIowkM BpTqNBeHEzQAlIhQuyu1ugmQtfsYYq6FPmWMRfFPes/4JUU/PQARAQABtCVOaXRlc2ggTmFy YXlhbiBMYWwgPG5pbGFsQHJlZGhhdC5jb20+iQI9BBMBCAAnBQJZeKUKAhsjBQkJZgGABQsJ CAcCBhUICQoLAgQWAgMBAh4BAheAAAoJEKOGQNwGMqM56lEP/A2KMs/pu0URcVk/kqVwcBhU SnvB8DP3lDWDnmVrAkFEOnPX7GTbactQ41wF/xwjwmEmTzLrMRZpkqz2y9mV0hWHjqoXbOCS 6RwK3ri5e2ThIPoGxFLt6TrMHgCRwm8YuOSJ97o+uohCTN8pmQ86KMUrDNwMqRkeTRW9wWIQ EdDqW44VwelnyPwcmWHBNNb1Kd8j3xKlHtnS45vc6WuoKxYRBTQOwI/5uFpDZtZ1a5kq9Ak/ MOPDDZpd84rqd+IvgMw5z4a5QlkvOTpScD21G3gjmtTEtyfahltyDK/5i8IaQC3YiXJCrqxE r7/4JMZeOYiKpE9iZMtS90t4wBgbVTqAGH1nE/ifZVAUcCtycD0f3egX9CHe45Ad4fsF3edQ ESa5tZAogiA4Hc/yQpnnf43a3aQ67XPOJXxS0Qptzu4vfF9h7kTKYWSrVesOU3QKYbjEAf95 NewF9FhAlYqYrwIwnuAZ8TdXVDYt7Z3z506//sf6zoRwYIDA8RDqFGRuPMXUsoUnf/KKPrtR ceLcSUP/JCNiYbf1/QtW8S6Ca/4qJFXQHp0knqJPGmwuFHsarSdpvZQ9qpxD3FnuPyo64S2N Dfq8TAeifNp2pAmPY2PAHQ3nOmKgMG8Gn5QiORvMUGzSz8Lo31LW58NdBKbh6bci5+t/HE0H pnyVf5xhNC/FuQINBFl4pQoBEACr+MgxWHUP76oNNYjRiNDhaIVtnPRqxiZ9v4H5FPxJy9UD Bqr54rifr1E+K+yYNPt/Po43vVL2cAyfyI/LVLlhiY4yH6T1n+Di/hSkkviCaf13gczuvgz4 KVYLwojU8+naJUsiCJw01MjO3pg9GQ+47HgsnRjCdNmmHiUQqksMIfd8k3reO9SUNlEmDDNB XuSzkHjE5y/R/6p8uXaVpiKPfHoULjNRWaFc3d2JGmxJpBdpYnajoz61m7XJlgwl/B5Ql/6B dHGaX3VHxOZsfRfugwYF9CkrPbyO5PK7yJ5vaiWre7aQ9bmCtXAomvF1q3/qRwZp77k6i9R3 tWfXjZDOQokw0u6d6DYJ0Vkfcwheg2i/Mf/epQl7Pf846G3PgSnyVK6cRwerBl5a68w7xqVU 4KgAh0DePjtDcbcXsKRT9D63cfyfrNE+ea4i0SVik6+N4nAj1HbzWHTk2KIxTsJXypibOKFX 2VykltxutR1sUfZBYMkfU4PogE7NjVEU7KtuCOSAkYzIWrZNEQrxYkxHLJsWruhSYNRsqVBy KvY6JAsq/i5yhVd5JKKU8wIOgSwC9P6mXYRgwPyfg15GZpnw+Fpey4bCDkT5fMOaCcS+vSU1 UaFmC4Ogzpe2BW2DOaPU5Ik99zUFNn6cRmOOXArrryjFlLT5oSOe4IposgWzdwARAQABiQIl BBgBCAAPBQJZeKUKAhsMBQkJZgGAAAoJEKOGQNwGMqM5ELoP/jj9d9gF1Al4+9bngUlYohYu 0sxyZo9IZ7Yb7cHuJzOMqfgoP4tydP4QCuyd9Q2OHHL5AL4VFNb8SvqAxxYSPuDJTI3JZwI7 d8JTPKwpulMSUaJE8ZH9n8A/+sdC3CAD4QafVBcCcbFe1jifHmQRdDrvHV9Es14QVAOTZhnJ vweENyHEIxkpLsyUUDuVypIo6y/Cws+EBCWt27BJi9GH/EOTB0wb+2ghCs/i3h8a+bi+bS7L FCCm/AxIqxRurh2UySn0P/2+2eZvneJ1/uTgfxnjeSlwQJ1BWzMAdAHQO1/lnbyZgEZEtUZJ x9d9ASekTtJjBMKJXAw7GbB2dAA/QmbA+Q+Xuamzm/1imigz6L6sOt2n/X/SSc33w8RJUyor SvAIoG/zU2Y76pKTgbpQqMDmkmNYFMLcAukpvC4ki3Sf086TdMgkjqtnpTkEElMSFJC8npXv 3QnGGOIfFug/qs8z03DLPBz9VYS26jiiN7QIJVpeeEdN/LKnaz5LO+h5kNAyj44qdF2T2AiF HxnZnxO5JNP5uISQH3FjxxGxJkdJ8jKzZV7aT37sC+Rp0o3KNc+GXTR+GSVq87Xfuhx0LRST NK9ZhT0+qkiN7npFLtNtbzwqaqceq3XhafmCiw8xrtzCnlB/C4SiBr/93Ip4kihXJ0EuHSLn VujM7c/b4pps Organization: Red Hat Inc, Message-ID: <33e41a02-7a9c-f166-8eb3-50abacb9d2cc@redhat.com> Date: Wed, 24 Jul 2019 15:07:42 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190724143902-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Wed, 24 Jul 2019 19:07:49 +0000 (UTC) Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 7/24/19 3:02 PM, Michael S. Tsirkin wrote: > On Wed, Jul 24, 2019 at 10:05:14AM -0700, Alexander Duyck wrote: >> From: Alexander Duyck >> >> 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 > Looking at the design, it seems that hinted pages can immediately be > reused. I wonder how we can efficiently support this > with kvm when poisoning is in effect. Of course we can just > ignore the poison. However it seems cleaner to > 1. verify page is poisoned with the correct value > 2. fill the page with the correct value on fault Once VIRTIO_BALLOON_F_PAGE_POISON user side support is available. Can't we just use that at the time of initialization? > Requirement 2 requires some kind of madvise that > will save the poison e.g. in the VMA. > > Not a blocker for sure ... > > >> --- >> 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 >> #include >> #include >> +#include >> >> /* >> * 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. */ > > can be an out of memory condition, and then ... > >> + virtqueue_add_inbuf(vq, ph_dev_info->sg, num_hints, vb, GFP_KERNEL); >> + virtqueue_kick(vq); > ... this will block forever. > >> + /* When host has read buffer, this completes via balloon_ack */ >> + wait_event(vb->acked, virtqueue_get_buf(vq, &unused)); > However below I suggest limiting capacity which will solve > this problem for you. > > > >> +} >> + >> 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; > As explained above I think you should limit this by vq size. > Otherwise virtqueue add buf might fail. > In fact by struct spec reading you need to limit it > anyway otherwise it will fail unconditionally. > In practice on most hypervisors it will typically work ... > >> + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_HINTING)) { >> + err = page_hinting_startup(&vb->ph_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); >> @@ -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