Message-ID: <2c3d0749-0f41-e064-0153-b6130268add2@kaspersky.com>
Date:   Wed, 21 Apr 2021 18:06:28 +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>,
        Colin Ian King <colin.king@...onical.com>,
        Andra Paraschiv <andraprs@...zon.com>,
        Norbert Slusarek <nslusarek@....net>,
        Alexander Popov <alex.popov@...ux.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 v8 00/19] virtio/vsock: introduce SOCK_SEQPACKET
 support


On 21.04.2021 12:52, Stefano Garzarella wrote:
> On Tue, Apr 13, 2021 at 03:39:51PM +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, new bit for field 'flags' was added: SEQ_EOR. This bit is
>> set to 1 in last RW packet of message.
>> 	Now as  packets of one socket are not reordered neither on vsock
>> nor on vhost transport layers, such bit allows to restore original
>> message on receiver's side. If user's buffer is smaller than message
>> 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_TRUNC' flags.
>> 	Tests also implemented.
>>
>> 	Thanks to stsp2@...dex.ru for encouragements and initial design
>> recommendations.
>>
>> Arseny Krasnov (19):
>>  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: 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: defines and constants for SEQPACKET
>>  virtio/vsock: dequeue callback for SOCK_SEQPACKET
>>  virtio/vsock: add SEQPACKET receive logic
>>  virtio/vsock: rest of SOCK_SEQPACKET support
>>  virtio/vsock: enable SEQPACKET for transport
>>  vhost/vsock: enable SEQPACKET for transport
>>  vsock/loopback: enable SEQPACKET for transport
>>  vsock_test: add SOCK_SEQPACKET tests
>>  virtio/vsock: update trace event for SEQPACKET
>>  af_vsock: serialize writes to shared socket
>>
>> drivers/vhost/vsock.c                        |  31 +-
>> include/linux/virtio_vsock.h                 |  11 +
>> include/net/af_vsock.h                       |   8 +
>> .../events/vsock_virtio_transport_common.h   |   5 +-
>> include/uapi/linux/virtio_vsock.h            |   9 +
>> net/vmw_vsock/af_vsock.c                     | 470 +++++++++++------
>> net/vmw_vsock/virtio_transport.c             |  17 +
>> net/vmw_vsock/virtio_transport_common.c      | 167 ++++--
>> net/vmw_vsock/vsock_loopback.c               |  12 +
>> tools/testing/vsock/util.c                   |  32 +-
>> tools/testing/vsock/util.h                   |   3 +
>> tools/testing/vsock/vsock_test.c             |  63 +++
>> 12 files changed, 625 insertions(+), 203 deletions(-)
>>
>> v7 -> v8:
>> General changelog:
>> - whole idea is simplified: channel now considered reliable,
>>   so SEQ_BEGIN, SEQ_END, 'msg_len' and 'msg_id' were removed.
>>   Only thing that is used to mark end of message is bit in
>>   'flags' field of packet header: VIRTIO_VSOCK_SEQ_EOR. Packet
>>   with such bit set to 1 means, that this is last packet of
>>   message.
>>
>> - POSIX MSG_EOR support is removed, as there is no exact
>>   description how it works.
> It would be nice to support it, I'll try to see if I can find anything.
>
> I just reviewed the series. I think the most important things to fix are 
> the `seqpacket_allow` stored in the struct virtio_transport that is 
> wrong IMHO, and use cpu_to_le32()/le32_to_cpu() to access the flags.

Thank You, i'll prepare next version. Main question is: does this

approach(no SEQ_BEGIN, SEQ_END, 'msg_len' and 'msg_id') considered

good? In this case it will be easier to prepare final version, because it

is smaller and more simple than previous logic. Also patch to spec

will be smaller.

>
> I also left some other comments around.
>
> Thanks,
> Stefano
>
>> - all changes to 'include/uapi/linux/virtio_vsock.h' moved
>>   to dedicated patch, as these changes linked with patch to
>>   spec.
>>
>> - patch 'virtio/vsock: SEQPACKET feature bit support' now merged
>>   to 'virtio/vsock: setup SEQPACKET ops for transport'.
>>
>> - patch 'vhost/vsock: SEQPACKET feature bit support' now merged
>>   to 'vhost/vsock: setup SEQPACKET ops for transport'.
>>
>> Per patch changelog:
>>  see every patch after '---' line.
>>
>> v6 -> v7:
>> General changelog:
>> - virtio transport callback for message length now removed
>>   from transport. Length of record is returned by dequeue
>>   callback.
>>
>> - function which tries to get message length now returns 0
>>   when rx queue is empty. Also length of current message in
>>   progress is set to 0, when message processed or error
>>   happens.
>>
>> - patches for virtio feature bit moved after patches with
>>   transport ops.
>>
>> Per patch changelog:
>>  see every patch after '---' line.
>>
>> 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.
>>
>> v4 -> v5:
>> - patches reorganized:
>>   1) Setting of packet's type in 'virtio_transport_send_pkt_info()'
>>      is moved to separate patch.
>>   2) Simplifying of 'virtio_transport_send_credit_update()' is
>>      moved to separate patch and before main virtio/vsock patches.
>> - style problem fixed
>> - in 'af_vsock: separate receive data loop' extra 'release_sock()'
>>   removed
>> - added trace event fields for SEQPACKET
>> - in 'af_vsock: separate wait data loop':
>>   1) 'vsock_wait_data()' removed 'goto out;'
>>   2) Comment for invalid data amount is changed.
>> - in 'af_vsock: rest of SEQPACKET support', 'new_transport' pointer
>>   check is moved after 'try_module_get()'
>> - in 'af_vsock: update comments for stream sockets', 'connect-oriented'
>>   replaced with 'connection-oriented'
>> - in 'loopback/vsock: setup SEQPACKET ops for transport',
>>   'loopback/vsock' replaced with 'vsock/loopback'
>>
>> v3 -> v4:
>> - SEQPACKET specific metadata moved from packet header to payload
>>   and called 'virtio_vsock_seq_hdr'
>> - record integrity check:
>>   1) SEQ_END operation was added, which marks end of record.
>>   2) Both SEQ_BEGIN and SEQ_END carries counter which is incremented
>>      on every marker send.
>> - af_vsock.c: socket operations for STREAM and SEQPACKET call same
>>   functions instead of having own "gates" differs only by names:
>>   'vsock_seqpacket/stream_getsockopt()' now replaced with
>>   'vsock_connectible_getsockopt()'.
>> - af_vsock.c: 'seqpacket_dequeue' callback returns error and flag that
>>   record ready. There is no need to return number of copied bytes,
>>   because case when record received successfully is checked at virtio
>>   transport layer, when SEQ_END is processed. Also user doesn't need
>>   number of copied bytes, because 'recv()' from SEQPACKET could return
>>   error, length of users's buffer or length of whole record(both are
>>   known in af_vsock.c).
>> - af_vsock.c: both wait loops in af_vsock.c(for data and space) moved
>>   to separate functions because now both called from several places.
>> - af_vsock.c: 'vsock_assign_transport()' checks that 'new_transport'
>>   pointer is not NULL and returns 'ESOCKTNOSUPPORT' instead of 'ENODEV'
>>   if failed to use transport.
>> - tools/testing/vsock/vsock_test.c: rename tests
>>
>> v2 -> v3:
>> - patches reorganized: split for prepare and implementation patches
>> - local variables are declared in "Reverse Christmas tree" manner
>> - virtio_transport_common.c: valid leXX_to_cpu() for vsock header
>>   fields access
>> - af_vsock.c: 'vsock_connectible_*sockopt()' added as shared code
>>   between stream and seqpacket sockets.
>> - af_vsock.c: loops in '__vsock_*_recvmsg()' refactored.
>> - af_vsock.c: 'vsock_wait_data()' refactored.
>>
>> v1 -> v2:
>> - patches reordered: af_vsock.c related changes now before virtio vsock
>> - patches reorganized: more small patches, where +/- are not mixed
>> - tests for SOCK_SEQPACKET added
>> - all commit messages updated
>> - af_vsock.c: 'vsock_pre_recv_check()' inlined to
>>   'vsock_connectible_recvmsg()'
>> - af_vsock.c: 'vsock_assign_transport()' returns ENODEV if transport
>>   was not found
>> - virtio_transport_common.c: transport callback for seqpacket dequeue
>> - virtio_transport_common.c: simplified
>>   'virtio_transport_recv_connected()'
>> - virtio_transport_common.c: send reset on socket and packet type
>> 			      mismatch.
>>
>> Signed-off-by: Arseny Krasnov <arseny.krasnov@...persky.com>
>>
>> -- 
>> 2.25.1
>>
>

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