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[79.34.249.199]) by smtp.gmail.com with ESMTPSA id g194sm20204347wme.39.2021.02.01.03.03.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 01 Feb 2021 03:03:01 -0800 (PST) Date: Mon, 1 Feb 2021 12:02:58 +0100 From: Stefano Garzarella To: Arseny Krasnov Subject: Re: [RFC PATCH v3 00/13] virtio/vsock: introduce SOCK_SEQPACKET support Message-ID: <20210201110258.7ze7a7izl7gesv4w@steredhat> References: <20210125110903.597155-1-arseny.krasnov@kaspersky.com> <20210128171923.esyna5ccv5s27jyu@steredhat> <63459bb3-da22-b2a4-71ee-e67660fd2e12@kaspersky.com> <20210129092604.mgaw3ipiyv6xra3b@steredhat> MIME-Version: 1.0 In-Reply-To: Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=sgarzare@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline Cc: Andra Paraschiv , "kvm@vger.kernel.org" , "Michael S. Tsirkin" , Jeff Vander Stoep , "stsp2@yandex.ru" , "linux-kernel@vger.kernel.org" , "virtualization@lists.linux-foundation.org" , "oxffffaa@gmail.com" , "netdev@vger.kernel.org" , Stefan Hajnoczi , Jakub Kicinski , Colin Ian King , "David S. Miller" X-BeenThere: virtualization@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Linux virtualization List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="iso-8859-1"; Format="flowed" Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" On Fri, Jan 29, 2021 at 06:52:23PM +0300, Arseny Krasnov wrote: > >On 29.01.2021 12:26, Stefano Garzarella wrote: >> On Fri, Jan 29, 2021 at 09:41:50AM +0300, Arseny Krasnov wrote: >>> On 28.01.2021 20:19, Stefano Garzarella wrote: >>>> Hi Arseny, >>>> I reviewed a part, tomorrow I hope to finish the other patches. >>>> >>>> Just a couple of comments in the TODOs below. >>>> >>>> On Mon, Jan 25, 2021 at 02:09:00PM +0300, Arseny Krasnov wrote: >>>>> This patchset impelements support of SOCK_SEQPACKET for virtio >>>>> transport. >>>>> As SOCK_SEQPACKET guarantees to save record boundaries, so to >>>>> do it, new packet operation was added: it marks start of record (with >>>>> record length in header), such packet doesn't carry any data. To send >>>>> record, packet with start marker is sent first, then all data is sent >>>>> as usual 'RW' packets. On receiver's side, length of record is known >>>> >from packet with start record marker. Now as packets of one socket >>>>> are not reordered neither on vsock nor on vhost transport layers, such >>>>> marker allows to restore original record on receiver's side. If user's >>>>> buffer is smaller that record length, when all out of size data is >>>>> dropped. >>>>> Maximum length of datagram is not limited as in stream socket, >>>>> because same credit logic is used. Difference with stream socket is >>>>> that user is not woken up until whole record is received or error >>>>> occurred. Implementation also supports 'MSG_EOR' and 'MSG_TRUNC' flag= s. >>>>> Tests also implemented. >>>>> >>>>> Arseny Krasnov (13): >>>>> af_vsock: prepare for SOCK_SEQPACKET support >>>>> af_vsock: prepare 'vsock_connectible_recvmsg()' >>>>> af_vsock: implement SEQPACKET rx loop >>>>> af_vsock: implement send logic for SOCK_SEQPACKET >>>>> af_vsock: rest of SEQPACKET support >>>>> af_vsock: update comments for stream sockets >>>>> virtio/vsock: dequeue callback for SOCK_SEQPACKET >>>>> virtio/vsock: fetch length for SEQPACKET record >>>>> virtio/vsock: add SEQPACKET receive logic >>>>> virtio/vsock: rest of SOCK_SEQPACKET support >>>>> virtio/vsock: setup SEQPACKET ops for transport >>>>> vhost/vsock: setup SEQPACKET ops for transport >>>>> vsock_test: add SOCK_SEQPACKET tests >>>>> >>>>> drivers/vhost/vsock.c | 7 +- >>>>> include/linux/virtio_vsock.h | 12 + >>>>> include/net/af_vsock.h | 6 + >>>>> include/uapi/linux/virtio_vsock.h | 9 + >>>>> net/vmw_vsock/af_vsock.c | 543 ++++++++++++++++------ >>>>> net/vmw_vsock/virtio_transport.c | 4 + >>>>> net/vmw_vsock/virtio_transport_common.c | 295 ++++++++++-- >>>>> tools/testing/vsock/util.c | 32 +- >>>>> tools/testing/vsock/util.h | 3 + >>>>> tools/testing/vsock/vsock_test.c | 126 +++++ >>>>> 10 files changed, 862 insertions(+), 175 deletions(-) >>>>> >>>>> TODO: >>>>> - Support for record integrity control. As transport could drop some >>>>> packets, something like "record-id" and record end marker need to >>>>> be implemented. Idea is that SEQ_BEGIN packet carries both record >>>>> length and record id, end marker(let it be SEQ_END) carries only >>>>> record id. To be sure that no one packet was lost, receiver checks >>>>> length of data between SEQ_BEGIN and SEQ_END(it must be same with >>>>> value in SEQ_BEGIN) and record ids of SEQ_BEGIN and SEQ_END(this >>>>> means that both markers were not dropped. I think that easiest way >>>>> to implement record id for SEQ_BEGIN is to reuse another field of >>>>> packet header(SEQ_BEGIN already uses 'flags' as record length).For >>>>> SEQ_END record id could be stored in 'flags'. >>>> I don't really like the idea of reusing the 'flags' field for this >>>> purpose. >>>> >>>>> Another way to implement it, is to move metadata of both SEQ_END >>>>> and SEQ_BEGIN to payload. But this approach has problem, because >>>>> if we move something to payload, such payload is accounted by >>>>> credit logic, which fragments payload, while payload with record >>>>> length and id couldn't be fragmented. One way to overcome it is to >>>>> ignore credit update for SEQ_BEGIN/SEQ_END packet.Another solution >>>>> is to update 'stream_has_space()' function: current implementation >>>>> return non-zero when at least 1 byte is allowed to use,but updated >>>>> version will have extra argument, which is needed length. For 'RW' >>>>> packet this argument is 1, for SEQ_BEGIN it is sizeof(record len + >>>>> record id) and for SEQ_END it is sizeof(record id). >>>> Is the payload accounted by credit logic also if hdr.op is not >>>> VIRTIO_VSOCK_OP_RW? >>> Yes, on send any packet with payload could be fragmented if >>> >>> there is not enough space at receiver. On receive 'fwd_cnt' and >>> >>> 'buf_alloc' are updated with header of every packet. Of course, >>> >>> to every such case i've described i can add check for 'RW' >>> >>> packet, to exclude payload from credit accounting, but this is >>> >>> bunch of dumb checks. >>> >>>> I think that we can define a specific header to put after the >>>> virtio_vsock_hdr when hdr.op is SEQ_BEGIN or SEQ_END, and in this head= er >>>> we can store the id and the length of the message. >>> I think it is better than use payload and touch credit logic >>> >> Cool, so let's try this option, hoping there aren't a lot of issues. > >If i understand, current implementation has 'struct virtio_vsock_hdr', > >then i'll add 'struct virtio_vsock_hdr_seq' with message length and id. > >After that, in 'struct virtio_vsock_pkt' which describes packet, field for > >header(which is 'struct virtio_vsock_hdr') must be replaced with new > >structure which=A0 contains both 'struct virtio_vsock_hdr' and 'struct > >virtio_vsock_hdr_seq', because header field of 'struct virtio_vsock_pkt' > >is buffer for virtio layer. After it all accesses to header(for example to > >'buf_alloc' field will go accross new=A0 structure with both headers: > >pkt->hdr.buf_alloc=A0=A0 ->=A0=A0 pkt->extended_hdr.classic_hdr.buf_alloc > >May be to avoid this, packet's header could be allocated dynamically > >in the same manner as packet's buffer? Size of allocation is always > >sizeof(classic header) + sizeof(seq header). In 'struct virtio_vsock_pkt' > >such header will be implemented as union of two pointers: class header > >and extended header containing classic and seq header. Which pointer > >to use is depends on packet's op. I think that the 'classic header' can stay as is, and the extended = header can be dynamically allocated, as we do for the payload. But we have to be careful what happens if the other peer doesn't support = SEQPACKET and if it counts this extra header as a payload for the credit = mechanism. I'll try to take a closer look in the next few days. Thanks, Stefano _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization