netdev - Re: [PATCH 3/5] VSOCK: support receive mergeable rx buffer in guest

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Message-ID: <1b67b8ef-5dcc-0383-1b32-d80f294533d3@redhat.com>
Date:   Wed, 7 Nov 2018 14:20:52 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     jiangyiwen <jiangyiwen@...wei.com>, stefanha@...hat.com
Cc:     netdev@...r.kernel.org, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH 3/5] VSOCK: support receive mergeable rx buffer in guest


On 2018/11/6 下午2:41, jiangyiwen wrote:
> On 2018/11/6 12:00, Jason Wang wrote:
>> On 2018/11/5 下午3:47, jiangyiwen wrote:
>>> Guest receive mergeable rx buffer, it can merge
>>> scatter rx buffer into a big buffer and then copy
>>> to user space.
>>>
>>> Signed-off-by: Yiwen Jiang<jiangyiwen@...wei.com>
>>> ---
>>>    include/linux/virtio_vsock.h            |  9 ++++
>>>    net/vmw_vsock/virtio_transport.c        | 75 +++++++++++++++++++++++++++++----
>>>    net/vmw_vsock/virtio_transport_common.c | 59 ++++++++++++++++++++++----
>>>    3 files changed, 127 insertions(+), 16 deletions(-)
>>>
>>> diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
>>> index da9e1fe..6be3cd7 100644
>>> --- a/include/linux/virtio_vsock.h
>>> +++ b/include/linux/virtio_vsock.h
>>> @@ -13,6 +13,8 @@
>>>    #define VIRTIO_VSOCK_DEFAULT_RX_BUF_SIZE    (1024 * 4)
>>>    #define VIRTIO_VSOCK_MAX_BUF_SIZE        0xFFFFFFFFUL
>>>    #define VIRTIO_VSOCK_MAX_PKT_BUF_SIZE        (1024 * 64)
>>> +/* virtio_vsock_pkt + max_pkt_len(default MAX_PKT_BUF_SIZE) */
>>> +#define VIRTIO_VSOCK_MAX_MRG_BUF_NUM ((VIRTIO_VSOCK_MAX_PKT_BUF_SIZE / PAGE_SIZE) + 1)
>>>
>>>    /* Virtio-vsock feature */
>>>    #define VIRTIO_VSOCK_F_MRG_RXBUF 0 /* Host can merge receive buffers. */
>>> @@ -48,6 +50,11 @@ struct virtio_vsock_sock {
>>>        struct list_head rx_queue;
>>>    };
>>>
>>> +struct virtio_vsock_mrg_rxbuf {
>>> +    void *buf;
>>> +    u32 len;
>>> +};
>>> +
>>>    struct virtio_vsock_pkt {
>>>        struct virtio_vsock_hdr    hdr;
>>>        struct virtio_vsock_mrg_rxbuf_hdr mrg_rxbuf_hdr;
>>> @@ -59,6 +66,8 @@ struct virtio_vsock_pkt {
>>>        u32 len;
>>>        u32 off;
>>>        bool reply;
>>> +    bool mergeable;
>>> +    struct virtio_vsock_mrg_rxbuf mrg_rxbuf[VIRTIO_VSOCK_MAX_MRG_BUF_NUM];
>>>    };
>> It's better to use iov here I think, and drop buf completely.
>>
>> And this is better to be done in an independent patch.
>>
> You're right, I can use kvec instead of customized structure,
> in addition, I don't understand about drop buf completely and
> an independent patch.


I mean there a void *buf in struct virtio_vsock_pkt. You can drop it and 
switch to use iov(iter) or other data structure that supports sg.

Thanks


>
> Thanks.
>