Date:   Mon, 15 Mar 2021 18:22:05 +0300
From:   Arseny Krasnov <arseny.krasnov@...persky.com>
To:     Stefano Garzarella <sgarzare@...hat.com>
CC:     Stefan Hajnoczi <stefanha@...hat.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jorgen Hansen <jhansen@...are.com>,
        Norbert Slusarek <nslusarek@....net>,
        Andra Paraschiv <andraprs@...zon.com>,
        Colin Ian King <colin.king@...onical.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stsp2@...dex.ru" <stsp2@...dex.ru>,
        "oxffffaa@...il.com" <oxffffaa@...il.com>
Subject: Re: [RFC PATCH v6 00/22] virtio/vsock: introduce SOCK_SEQPACKET
 support


On 15.03.2021 14:40, Stefano Garzarella wrote:
> Hi Arseny,
>
> On Sun, Mar 07, 2021 at 08:57:19PM +0300, Arseny Krasnov wrote:
>> 	This patchset implements support of SOCK_SEQPACKET for virtio
>> transport.
>> 	As SOCK_SEQPACKET guarantees to save record boundaries, so to
>> do it, two new packet operations were added: first for start of record
>> and second to mark end of record(SEQ_BEGIN and SEQ_END later). Also,
>> both operations carries metadata - to maintain boundaries and payload
>> integrity. Metadata is introduced by adding special header with two
>> fields - message id and message length:
>>
>> 	struct virtio_vsock_seq_hdr {
>> 		__le32  msg_id;
>> 		__le32  msg_len;
>> 	} __attribute__((packed));
>>
>> 	This header is transmitted as payload of SEQ_BEGIN and SEQ_END
>> packets(buffer of second virtio descriptor in chain) in the same way as
>> data transmitted in RW packets. Payload was chosen as buffer for this
>> header to avoid touching first virtio buffer which carries header of
>> packet, because someone could check that size of this buffer is equal
>> to size of packet header. To send record, packet with start marker is
>> sent first(it's header carries length of record and id),then all data
>> is sent as usual 'RW' packets and finally SEQ_END is sent(it carries
>> id of message, which is equal to id of SEQ_BEGIN), also after sending
>> SEQ_END id is incremented. On receiver's side,size of record is known
> >from packet with start record marker. To check that no packets were
>> dropped by transport, 'msg_id's of two sequential SEQ_BEGIN and SEQ_END
>> are checked to be equal and length of data between two markers is
>> compared to then length in SEQ_BEGIN header.
>> 	Now as  packets of one socket are not reordered neither on
>> vsock nor on vhost transport layers, such markers 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' flags.
>> 	Tests also implemented.
>>
>> 	Thanks to stsp2@...dex.ru for encouragements and initial design
>> recommendations.
>>
>> Arseny Krasnov (22):
>>  af_vsock: update functions for connectible socket
>>  af_vsock: separate wait data loop
>>  af_vsock: separate receive data loop
>>  af_vsock: implement SEQPACKET receive loop
>>  af_vsock: separate wait space loop
>>  af_vsock: implement send logic for SEQPACKET
>>  af_vsock: rest of SEQPACKET support
>>  af_vsock: update comments for stream sockets
>>  virtio/vsock: set packet's type in virtio_transport_send_pkt_info()
>>  virtio/vsock: simplify credit update function API
>>  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: SEQPACKET feature bit
>>  vhost/vsock: SEQPACKET feature bit support
>>  virtio/vsock: SEQPACKET feature bit support
>>  virtio/vsock: setup SEQPACKET ops for transport
>>  vhost/vsock: setup SEQPACKET ops for transport
>>  vsock/loopback: setup SEQPACKET ops for transport
>>  vsock_test: add SOCK_SEQPACKET tests
>>  virtio/vsock: update trace event for SEQPACKET
>>
>> drivers/vhost/vsock.c                        |  22 +-
>> include/linux/virtio_vsock.h                 |  22 +
>> include/net/af_vsock.h                       |  10 +
>> .../events/vsock_virtio_transport_common.h   |  48 +-
>> include/uapi/linux/virtio_vsock.h            |  19 +
>> net/vmw_vsock/af_vsock.c                     | 589 +++++++++++------
>> net/vmw_vsock/virtio_transport.c             |  18 +
>> net/vmw_vsock/virtio_transport_common.c      | 364 ++++++++--
>> net/vmw_vsock/vsock_loopback.c               |  13 +
>> tools/testing/vsock/util.c                   |  32 +-
>> tools/testing/vsock/util.h                   |   3 +
>> tools/testing/vsock/vsock_test.c             | 126 ++++
>> 12 files changed, 1013 insertions(+), 253 deletions(-)
>>
>> v5 -> v6:
>> General changelog:
>> - virtio transport specific callbacks which send SEQ_BEGIN or
>>   SEQ_END now hidden inside virtio transport. Only enqueue,
>>   dequeue and record length callbacks are provided by transport.
>>
>> - virtio feature bit for SEQPACKET socket support introduced:
>>   VIRTIO_VSOCK_F_SEQPACKET.
>>
>> - 'msg_cnt' field in 'struct virtio_vsock_seq_hdr' renamed to
>>   'msg_id' and used as id.
>>
>> Per patch changelog:
>> - 'af_vsock: separate wait data loop':
>>    1) Commit message updated.
>>    2) 'prepare_to_wait()' moved inside while loop(thanks to
>>      Jorgen Hansen).
>>    Marked 'Reviewed-by' with 1), but as 2) I removed R-b.
>>
>> - 'af_vsock: separate receive data loop': commit message
>>    updated.
>>    Marked 'Reviewed-by' with that fix.
>>
>> - 'af_vsock: implement SEQPACKET receive loop': style fixes.
>>
>> - 'af_vsock: rest of SEQPACKET support':
>>    1) 'module_put()' added when transport callback check failed.
>>    2) Now only 'seqpacket_allow()' callback called to check
>>       support of SEQPACKET by transport.
>>
>> - 'af_vsock: update comments for stream sockets': commit message
>>    updated.
>>    Marked 'Reviewed-by' with that fix.
>>
>> - 'virtio/vsock: set packet's type in send':
>>    1) Commit message updated.
>>    2) Parameter 'type' from 'virtio_transport_send_credit_update()'
>>       also removed in this patch instead of in next.
>>
>> - 'virtio/vsock: dequeue callback for SOCK_SEQPACKET': SEQPACKET
>>    related state wrapped to special struct.
>>
>> - 'virtio/vsock: update trace event for SEQPACKET': format strings
>>    now not broken by new lines.
> I left a bunch of comments in the patches, I hope they are easy to fix 
> :-)
Thank you, yes, there are still small fixes.
>
> Thanks for the changelogs. About 'per patch changelog', it is very 
> useful!
> Just a suggestion, I think is better to include them in each patch after 
> the '---' to simplify the review.
Ack
>
> You can use git-notes(1) or you can simply edit the format-patch and add 
> the changelog after the 3 dashes, so that they are ignored when the 
> patch is applied.
>
> Thanks,
> Stefano
>
>

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