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Fri, 24 Apr 2020 11:20:21 +0000 (UTC) Received: from [10.36.113.138] (ovpn-113-138.ams2.redhat.com [10.36.113.138]) by smtp.corp.redhat.com (Postfix) with ESMTP id 72D056084C; Fri, 24 Apr 2020 11:20:17 +0000 (UTC) Subject: Re: [PATCH v21 QEMU 5/5] virtio-balloon: Provide an interface for free page reporting To: Alexander Duyck , mst@redhat.com References: <20200422181649.12258.37077.stgit@localhost.localdomain> <20200422182127.12258.26300.stgit@localhost.localdomain> From: David Hildenbrand Autocrypt: addr=david@redhat.com; prefer-encrypt=mutual; keydata= mQINBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABtCREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT6JAlgEEwEIAEICGwMFCQlmAYAGCwkIBwMCBhUI AgkKCwQWAgMBAh4BAheAFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl3pImkCGQEACgkQTd4Q 9wD/g1o+VA//SFvIHUAvul05u6wKv/pIR6aICPdpF9EIgEU448g+7FfDgQwcEny1pbEzAmiw zAXIQ9H0NZh96lcq+yDLtONnXk/bEYWHHUA014A1wqcYNRY8RvY1+eVHb0uu0KYQoXkzvu+s Dncuguk470XPnscL27hs8PgOP6QjG4jt75K2LfZ0eAqTOUCZTJxA8A7E9+XTYuU0hs7QVrWJ jQdFxQbRMrYz7uP8KmTK9/Cnvqehgl4EzyRaZppshruKMeyheBgvgJd5On1wWq4ZUV5PFM4x II3QbD3EJfWbaJMR55jI9dMFa+vK7MFz3rhWOkEx/QR959lfdRSTXdxs8V3zDvChcmRVGN8U Vo93d1YNtWnA9w6oCW1dnDZ4kgQZZSBIjp6iHcA08apzh7DPi08jL7M9UQByeYGr8KuR4i6e RZI6xhlZerUScVzn35ONwOC91VdYiQgjemiVLq1WDDZ3B7DIzUZ4RQTOaIWdtXBWb8zWakt/ ztGhsx0e39Gvt3391O1PgcA7ilhvqrBPemJrlb9xSPPRbaNAW39P8ws/UJnzSJqnHMVxbRZC Am4add/SM+OCP0w3xYss1jy9T+XdZa0lhUvJfLy7tNcjVG/sxkBXOaSC24MFPuwnoC9WvCVQ ZBxouph3kqc4Dt5X1EeXVLeba+466P1fe1rC8MbcwDkoUo65Ag0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAGJAiUEGAECAA8FAlXLn5ECGwwFCQlmAYAACgkQTd4Q 9wD/g1qA6w/+M+ggFv+JdVsz5+ZIc6MSyGUozASX+bmIuPeIecc9UsFRatc91LuJCKMkD9Uv GOcWSeFpLrSGRQ1Z7EMzFVU//qVs6uzhsNk0RYMyS0B6oloW3FpyQ+zOVylFWQCzoyyf227y GW8HnXunJSC+4PtlL2AY4yZjAVAPLK2l6mhgClVXTQ/S7cBoTQKP+jvVJOoYkpnFxWE9pn4t H5QIFk7Ip8TKr5k3fXVWk4lnUi9MTF/5L/mWqdyIO1s7cjharQCstfWCzWrVeVctpVoDfJWp 4LwTuQ5yEM2KcPeElLg5fR7WB2zH97oI6/Ko2DlovmfQqXh9xWozQt0iGy5tWzh6I0JrlcxJ ileZWLccC4XKD1037Hy2FLAjzfoWgwBLA6ULu0exOOdIa58H4PsXtkFPrUF980EEibUp0zFz GotRVekFAceUaRvAj7dh76cToeZkfsjAvBVb4COXuhgX6N4pofgNkW2AtgYu1nUsPAo+NftU CxrhjHtLn4QEBpkbErnXQyMjHpIatlYGutVMS91XTQXYydCh5crMPs7hYVsvnmGHIaB9ZMfB njnuI31KBiLUks+paRkHQlFcgS2N3gkRBzH7xSZ+t7Re3jvXdXEzKBbQ+dC3lpJB0wPnyMcX FOTT3aZT7IgePkt5iC/BKBk3hqKteTnJFeVIT7EC+a6YUFg= Organization: Red Hat GmbH Message-ID: Date: Fri, 24 Apr 2020 13:20:16 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <20200422182127.12258.26300.stgit@localhost.localdomain> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=205.139.110.120; envelope-from=david@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/04/24 03:54:07 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] X-Received-From: 205.139.110.120 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: virtio-dev@lists.oasis-open.org, qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 22.04.20 20:21, Alexander Duyck wrote: > From: Alexander Duyck >=20 > Add support for free page reporting. The idea is to function very similar > to how the balloon works in that we basically end up madvising the page a= s > not being used. However we don't really need to bother with any deflate > type logic since the page will be faulted back into the guest when it is > read or written to. >=20 > This provides a new way of letting the guest proactively report free > pages to the hypervisor, so the hypervisor can reuse them. In contrast to > inflate/deflate that is triggered via the hypervisor explicitly. >=20 > Signed-off-by: Alexander Duyck > --- > hw/virtio/virtio-balloon.c | 70 ++++++++++++++++++++++++++++++= ++++++ > include/hw/virtio/virtio-balloon.h | 2 + > 2 files changed, 71 insertions(+), 1 deletion(-) >=20 > diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c > index 5effc8b4653b..b473ff7f4b88 100644 > --- a/hw/virtio/virtio-balloon.c > +++ b/hw/virtio/virtio-balloon.c > @@ -321,6 +321,60 @@ 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; > + Maybe add a comment like /* * As discarded pages will be zero when re-accessed, all pages either * have the old value, or were zeroed out. In case the guest expects * another value, make sure to never discard. */ Whatever you think is best. > + if (qemu_balloon_is_inhibited() || dev->poison_val) { > + goto skip_element; > + } > + > + 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; > + RAMBlock *rb; > + > + /* > + * There is no need to check the memory section to see if > + * it is ram/readonly/romd like there is for handle_output > + * below. If the region is not meant to be written to then > + * address_space_map will have allocated a bounce buffer > + * and it will be freed in address_space_unmap and trigger > + * and unassigned_mem_write before failing to copy over the > + * buffer. If more than one bad descriptor is provided it > + * will return NULL after the first bounce buffer and fail > + * to map any resources. > + */ > + rb =3D qemu_ram_block_from_host(addr, false, &ram_offset); > + if (!rb) { > + trace_virtio_balloon_bad_addr(elem->in_addr[i]); > + continue; > + } > + > + /* > + * For now we will simply ignore unaligned memory regions, o= r > + * regions that overrun the end of the RAMBlock. > + */ > + if (!QEMU_IS_ALIGNED(ram_offset | size, qemu_ram_pagesize(rb= )) || > + (ram_offset + size) > qemu_ram_get_used_length(rb)) { > + continue; > + } > + > + ram_block_discard_range(rb, ram_offset, size); > + } > + > +skip_element: > + 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); > @@ -782,6 +836,16 @@ static void virtio_balloon_device_realize(DeviceStat= e *dev, Error **errp) > VirtIOBalloon *s =3D VIRTIO_BALLOON(dev); > int ret; > =20 > + /* > + * Page reporting is dependant on page poison to make sure we can > + * report a page without changing the state of the internal data. > + * We need to set the flag before we call virtio_init as it will > + * affect the config size of the vdev. > + */ > + if (virtio_has_feature(s->host_features, VIRTIO_BALLOON_F_REPORTING)= ) { > + s->host_features |=3D 1 << VIRTIO_BALLOON_F_PAGE_POISON; > + } > + As discussed, this hunk would go away. With that, this patch is really minimal, which is good :) > virtio_init(vdev, "virtio-balloon", VIRTIO_ID_BALLOON, > virtio_balloon_config_size(s)); > =20 > @@ -798,6 +862,10 @@ static void virtio_balloon_device_realize(DeviceStat= e *dev, Error **errp) > s->dvq =3D virtio_add_queue(vdev, 128, virtio_balloon_handle_output)= ; > s->svq =3D virtio_add_queue(vdev, 128, virtio_balloon_receive_stats)= ; > =20 > + if (virtio_has_feature(s->host_features, VIRTIO_BALLOON_F_REPORTING)= ) { > + s->rvq =3D virtio_add_queue(vdev, 32, virtio_balloon_handle_repo= rt); > + } > + > 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, > @@ -923,6 +991,8 @@ static Property virtio_balloon_properties[] =3D { > VIRTIO_BALLOON_F_DEFLATE_ON_OOM, false), > DEFINE_PROP_BIT("free-page-hint", VirtIOBalloon, host_features, > VIRTIO_BALLOON_F_FREE_PAGE_HINT, false), > + DEFINE_PROP_BIT("free-page-reporting", VirtIOBalloon, host_features, > + VIRTIO_BALLOON_F_REPORTING, true), I think you'll have to similarly disable it via compat machines if you want to default enable. Otherwise, backward migration would be broken. Also, I do wonder if we want to default-enable it. It can still have a negative performance impact and some people might not want that. Apart from that, looks good to me. Nothing else we have to migrate AFAIKs. --=20 Thanks, David / dhildenb