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[209.132.183.28]) by mx.google.com with ESMTPS id n9si32106365qte.44.2019.08.06.08.40.26 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 06 Aug 2019 08:40:26 -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-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id AAB6EFA8C0; Tue, 6 Aug 2019 15:40:25 +0000 (UTC) Received: from [10.40.205.241] (unknown [10.40.205.241]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 76F8460619; Tue, 6 Aug 2019 15:40:17 +0000 (UTC) Subject: Re: [PATCH v3 6/6] virtio-balloon: Add support for providing unused page reports to host To: Alexander Duyck , "Michael S. Tsirkin" Cc: Alexander Duyck , 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, willy@infradead.org, lcapitulino@redhat.com, wei.w.wang@intel.com, aarcange@redhat.com, pbonzini@redhat.com, dan.j.williams@intel.com References: <20190801222158.22190.96964.stgit@localhost.localdomain> <20190801223829.22190.36831.stgit@localhost.localdomain> <1cff09a4-d302-639c-ab08-9d82e5fc1383@redhat.com> <20190806073047-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: <85b045b4-9d43-6929-49b9-786bd25eaed2@redhat.com> Date: Tue, 6 Aug 2019 11:40:13 -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: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Tue, 06 Aug 2019 15:40:25 +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 8/6/19 11:16 AM, Alexander Duyck wrote: > On Tue, 2019-08-06 at 07:31 -0400, Michael S. Tsirkin wrote: >> On Mon, Aug 05, 2019 at 09:27:16AM -0700, Alexander Duyck wrote: >>> On Mon, 2019-08-05 at 12:00 -0400, Nitesh Narayan Lal wrote: >>>> On 8/1/19 6:38 PM, 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. >>>>> >>>>> Signed-off-by: Alexander Duyck >>>>> --- >>>>> drivers/virtio/Kconfig | 1 + >>>>> drivers/virtio/virtio_balloon.c | 56 +++++++++++++++++++++++++++++++++++ >>>>> include/uapi/linux/virtio_balloon.h | 1 + >>>>> 3 files changed, 58 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 2c19457ab573..971fe924e34f 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 >>>>> @@ -37,6 +38,9 @@ >>>>> #define VIRTIO_BALLOON_FREE_PAGE_SIZE \ >>>>> (1 << (VIRTIO_BALLOON_FREE_PAGE_ORDER + PAGE_SHIFT)) >>>>> >>>>> +/* limit on the number of pages that can be on the reporting vq */ >>>>> +#define VIRTIO_BALLOON_VRING_HINTS_MAX 16 >>>>> + >>>>> #ifdef CONFIG_BALLOON_COMPACTION >>>>> static struct vfsmount *balloon_mnt; >>>>> #endif >>>>> @@ -46,6 +50,7 @@ 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 >>>>> }; >>>>> >>>>> @@ -113,6 +118,10 @@ struct virtio_balloon { >>>>> >>>>> /* To register a shrinker to shrink memory upon memory pressure */ >>>>> struct shrinker shrinker; >>>>> + >>>>> + /* Unused page reporting device */ >>>>> + struct virtqueue *reporting_vq; >>>>> + struct page_reporting_dev_info ph_dev_info; >>>>> }; >>>>> >>>>> static struct virtio_device_id id_table[] = { >>>>> @@ -152,6 +161,23 @@ static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq) >>>>> >>>>> } >>>>> >>>>> +void virtballoon_unused_page_report(struct page_reporting_dev_info *ph_dev_info, >>>>> + unsigned int nents) >>>>> +{ >>>>> + struct virtio_balloon *vb = >>>>> + container_of(ph_dev_info, struct virtio_balloon, ph_dev_info); >>>>> + struct virtqueue *vq = vb->reporting_vq; >>>>> + unsigned int unused; >>>>> + >>>>> + /* We should always be able to add these buffers to an empty queue. */ >>>>> + virtqueue_add_inbuf(vq, ph_dev_info->sg, nents, vb, >>>>> + GFP_NOWAIT | __GFP_NOWARN); >>>> I think you should handle allocation failure here. It is a possibility, isn't? >>>> Maybe return an error or even disable page hinting/reporting? >>>> >>> I don't think it is an issue I have to worry about. Specifically I am >>> limiting the size of the scatterlist based on the size of the vq. As such >>> I will never exceed the size and should be able to use it to store the >>> scatterlist directly. >> I agree. But it can't hurt to BUG_ON for good measure. >> > I wouldn't use a BUG_ON as that seems overkill. No need to panic the > kernel just because we couldn't report some idle pages. > > I can probably do something like: > if (WARN_ON(err)) > return; +1 > > That way the unused page reporting can run to completion still and the > fact that we aren't really hinting on the pages would effectively be no > different then if we had a direct assigned device or shared memory in the > hypervisor. >