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Thu, 9 Apr 2020 17:35:37 +0000 (UTC) Received: from [10.36.113.222] (ovpn-113-222.ams2.redhat.com [10.36.113.222]) by smtp.corp.redhat.com (Postfix) with ESMTP id 54F8952735; Thu, 9 Apr 2020 17:35:33 +0000 (UTC) Subject: Re: [PATCH v18 QEMU 3/3] virtio-balloon: Provide a interface for free page reporting To: Alexander Duyck References: <20200408225302.18764.209.stgit@localhost.localdomain> <20200408225529.18764.44086.stgit@localhost.localdomain> <06ac44b9-77ae-7686-8a65-7edff2cbf1b7@redhat.com> 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: <987022c8-3aed-dccb-df02-d834500c04d3@redhat.com> Date: Thu, 9 Apr 2020 19:35:32 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: 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: 7bit X-detected-operating-system: by eggs.gnu.org: GNU/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, "Michael S. Tsirkin" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 09.04.20 19:34, Alexander Duyck wrote: > On Thu, Apr 9, 2020 at 12:44 AM David Hildenbrand wrote: >> >> On 09.04.20 00:55, Alexander Duyck wrote: >>> From: Alexander Duyck >>> >>> Add support for what I am referring to as "free page reporting". >> >> "Add support for "free 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. However >> >> I'd get rid of one "basically". >> >>> 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. >>> >>> 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 assuming >> >> It's not really a simplification, it's something new. It's a new way of >> letting the guest automatically report free pages to the hypervisor, so >> the hypervisor can reuse them. In contrast to inflate/deflate, that's >> triggered via the hypervisor explicitly. >> >>> 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 ones >>> haven't. >> >> "I assume this is safe" does not sound very confident. Can we just drop >> the last sentence? > > Agreed. I will make the requested changes to the patch description. > >> >>> >>> Signed-off-by: Alexander Duyck >>> --- >>> hw/virtio/virtio-balloon.c | 48 +++++++++++++++++++++++++++++++++++- >>> include/hw/virtio/virtio-balloon.h | 2 +- >>> 2 files changed, 47 insertions(+), 3 deletions(-) >>> >>> diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c >>> index 1c6d36a29a04..297b267198ac 100644 >>> --- a/hw/virtio/virtio-balloon.c >>> +++ b/hw/virtio/virtio-balloon.c >>> @@ -321,6 +321,42 @@ static void balloon_stats_set_poll_interval(Object *obj, Visitor *v, >>> balloon_stats_change_timer(s, 0); >>> } >>> >>> +static void virtio_balloon_handle_report(VirtIODevice *vdev, VirtQueue *vq) >>> +{ >>> + VirtIOBalloon *dev = VIRTIO_BALLOON(vdev); >>> + VirtQueueElement *elem; >>> + >>> + while ((elem = virtqueue_pop(vq, sizeof(VirtQueueElement)))) { >>> + unsigned int i; >>> + >>> + for (i = 0; i < elem->in_num; i++) { >>> + void *addr = elem->in_sg[i].iov_base; >>> + size_t size = 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; >>> + } >> >> These checks are not sufficient. See virtio_balloon_handle_output(), >> where we e.g., check that somebody doesn't try to discard the bios. >> >> Maybe we can factor our/unify the handling in both code paths. > > I am going to have to look at this further. If I understand correctly > you are asking me to add all of the memory section checks that are in > virtio_balloon_handle_output correct? > > I'm not sure it makes sense with the scatterlist approach I have taken > here. All of the mappings were created as a scatterlist of writable > DMA mappings unlike the regular balloon which is just stuffing PFN > numbers into an array and then sending the array across. As such I > would think there are already such protections in place. For instance, > you wouldn't want to let virtio-net map the BIOS and request data be > written into that either, correct? So I am assuming there is something > there to prevent that already isn't there? Good point, let's find out :) -- Thanks, David / dhildenb