netdev - Re: [PATCH net-next v5 0/6] virtio/vsock: introduce MSG

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Message-ID: <4558e96b-6330-667f-955b-b689986f884f@kaspersky.com>
Date:   Sun, 5 Sep 2021 19:02:44 +0300
From:   Arseny Krasnov <arseny.krasnov@...persky.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
CC:     Stefan Hajnoczi <stefanha@...hat.com>,
        Stefano Garzarella <sgarzare@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Colin Ian King <colin.king@...onical.com>,
        Norbert Slusarek <nslusarek@....net>,
        Andra Paraschiv <andraprs@...zon.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: [PATCH net-next v5 0/6] virtio/vsock: introduce MSG_EOR flag for
 SEQPACKET


On 05.09.2021 18:55, Michael S. Tsirkin wrote:
> On Fri, Sep 03, 2021 at 03:30:13PM +0300, Arseny Krasnov wrote:
>> 	This patchset implements support of MSG_EOR bit for SEQPACKET
>> AF_VSOCK sockets over virtio transport.
>> 	First we need to define 'messages' and 'records' like this:
>> Message is result of sending calls: 'write()', 'send()', 'sendmsg()'
>> etc. It has fixed maximum length, and it bounds are visible using
>> return from receive calls: 'read()', 'recv()', 'recvmsg()' etc.
>> Current implementation based on message definition above.
>> 	Record has unlimited length, it consists of multiple message,
>> and bounds of record are visible via MSG_EOR flag returned from
>> 'recvmsg()' call. Sender passes MSG_EOR to sending system call and
>> receiver will see MSG_EOR when corresponding message will be processed.
>> 	Idea of patchset comes from POSIX: it says that SEQPACKET
>> supports record boundaries which are visible for receiver using
>> MSG_EOR bit. So, it looks like MSG_EOR is enough thing for SEQPACKET
>> and we don't need to maintain boundaries of corresponding send -
>> receive system calls. But, for 'sendXXX()' and 'recXXX()' POSIX says,
>> that all these calls operates with messages, e.g. 'sendXXX()' sends
>> message, while 'recXXX()' reads messages and for SEQPACKET, 'recXXX()'
>> must read one entire message from socket, dropping all out of size
>> bytes. Thus, both message boundaries and MSG_EOR bit must be supported
>> to follow POSIX rules.
>> 	To support MSG_EOR new bit was added along with existing
>> 'VIRTIO_VSOCK_SEQ_EOR': 'VIRTIO_VSOCK_SEQ_EOM'(end-of-message) - now it
>> works in the same way as 'VIRTIO_VSOCK_SEQ_EOR'. But 'VIRTIO_VSOCK_SEQ_EOR'
>> is used to mark 'MSG_EOR' bit passed from userspace.
>> 	This patchset includes simple test for MSG_EOR.
>
> I'm prepared to merge this for this window,
> but I'm not sure who's supposed to ack the net/vmw_vsock/af_vsock.c
> bits. It's a harmless variable renaming so maybe it does not matter.
>
> The rest is virtio stuff so I guess my tree is ok.
>
> Objections, anyone?

https://lkml.org/lkml/2021/9/3/76 this is v4. It is same as v5 in af_vsock.c changes.

It has Reviewed by from Stefano Garzarella.

>
>
>>  Arseny Krasnov(6):
>>   virtio/vsock: rename 'EOR' to 'EOM' bit.
>>   virtio/vsock: add 'VIRTIO_VSOCK_SEQ_EOR' bit.
>>   vhost/vsock: support MSG_EOR bit processing
>>   virtio/vsock: support MSG_EOR bit processing
>>   af_vsock: rename variables in receive loop
>>   vsock_test: update message bounds test for MSG_EOR
>>
>>  drivers/vhost/vsock.c                   | 28 +++++++++++++----------
>>  include/uapi/linux/virtio_vsock.h       |  3 ++-
>>  net/vmw_vsock/af_vsock.c                | 10 ++++----
>>  net/vmw_vsock/virtio_transport_common.c | 23 ++++++++++++-------
>>  tools/testing/vsock/vsock_test.c        |  8 ++++++-
>>  5 files changed, 45 insertions(+), 27 deletions(-)
>>
>>  v4 -> v5:
>>  - Move bitwise and out of le32_to_cpu() in 0003.
>>
>>  v3 -> v4:
>>  - 'sendXXX()' renamed to 'send*()' in 0002- commit msg.
>>  - Comment about bit restore updated in 0003-.
>>  - 'same' renamed to 'similar' in 0003- commit msg.
>>  - u32 used instead of uint32_t in 0003-.
>>
>>  v2 -> v3:
>>  - 'virtio/vsock: rename 'EOR' to 'EOM' bit.' - commit message updated.
>>  - 'VIRTIO_VSOCK_SEQ_EOR' bit add moved to separate patch.
>>  - 'vhost/vsock: support MSG_EOR bit processing' - commit message
>>    updated.
>>  - 'vhost/vsock: support MSG_EOR bit processing' - removed unneeded
>>    'le32_to_cpu()', because input argument was already in CPU
>>    endianness.
>>
>>  v1 -> v2:
>>  - 'VIRTIO_VSOCK_SEQ_EOR' is renamed to 'VIRTIO_VSOCK_SEQ_EOM', to
>>    support backward compatibility.
>>  - use bitmask of flags to restore in vhost.c, instead of separated
>>    bool variable for each flag.
>>  - test for EAGAIN removed, as logically it is not part of this
>>    patchset(will be sent separately).
>>  - cover letter updated(added part with POSIX description).
>>
>> Signed-off-by: Arseny Krasnov <arseny.krasnov@...persky.com>
>> -- 
>> 2.25.1
>