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Message-ID: <obbppqyhstsuh3p3p4v6ipu7gl4z2ufeubvpv3dftyxubdvs5n@f7ugbp62xos7>
Date: Tue, 30 Jul 2024 10:22:00 +0200
From: Stefano Garzarella <sgarzare@...hat.com>
To: Amery Hung <ameryhung@...il.com>
Cc: stefanha@...hat.com, mst@...hat.com, jasowang@...hat.com,
xuanzhuo@...ux.alibaba.com, davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
pabeni@...hat.com, kys@...rosoft.com, haiyangz@...rosoft.com, wei.liu@...nel.org,
decui@...rosoft.com, bryantan@...are.com, vdasa@...are.com, pv-drivers@...are.com,
dan.carpenter@...aro.org, simon.horman@...igine.com, oxffffaa@...il.com,
kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org,
netdev@...r.kernel.org, linux-kernel@...r.kernel.org, linux-hyperv@...r.kernel.org,
bpf@...r.kernel.org, bobby.eshleman@...edance.com, jiang.wang@...edance.com,
amery.hung@...edance.com, xiyou.wangcong@...il.com
Subject: Re: [RFC PATCH net-next v6 07/14] virtio/vsock: add common datagram
send path
On Fri, Jul 26, 2024 at 04:22:16PM GMT, Amery Hung wrote:
>On Tue, Jul 23, 2024 at 7:42 AM Stefano Garzarella <sgarzare@...hat.com> wrote:
>>
>> On Wed, Jul 10, 2024 at 09:25:48PM GMT, Amery Hung wrote:
>> >From: Bobby Eshleman <bobby.eshleman@...edance.com>
>> >
>> >This commit implements the common function
>> >virtio_transport_dgram_enqueue for enqueueing datagrams. It does not add
>> >usage in either vhost or virtio yet.
>> >
>> >Signed-off-by: Bobby Eshleman <bobby.eshleman@...edance.com>
>> >Signed-off-by: Amery Hung <amery.hung@...edance.com>
>> >---
>> > include/linux/virtio_vsock.h | 1 +
>> > include/net/af_vsock.h | 2 +
>> > net/vmw_vsock/af_vsock.c | 2 +-
>> > net/vmw_vsock/virtio_transport_common.c | 87 ++++++++++++++++++++++++-
>> > 4 files changed, 90 insertions(+), 2 deletions(-)
>> >
>> >diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
>> >index f749a066af46..4408749febd2 100644
>> >--- a/include/linux/virtio_vsock.h
>> >+++ b/include/linux/virtio_vsock.h
>> >@@ -152,6 +152,7 @@ struct virtio_vsock_pkt_info {
>> > u16 op;
>> > u32 flags;
>> > bool reply;
>> >+ u8 remote_flags;
>> > };
>> >
>> > struct virtio_transport {
>> >diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h
>> >index 44db8f2c507d..6e97d344ac75 100644
>> >--- a/include/net/af_vsock.h
>> >+++ b/include/net/af_vsock.h
>> >@@ -216,6 +216,8 @@ void vsock_for_each_connected_socket(struct vsock_transport *transport,
>> > void (*fn)(struct sock *sk));
>> > int vsock_assign_transport(struct vsock_sock *vsk, struct vsock_sock *psk);
>> > bool vsock_find_cid(unsigned int cid);
>> >+const struct vsock_transport *vsock_dgram_lookup_transport(unsigned int cid,
>> >+ __u8 flags);
>>
>> Why __u8 and not just u8?
>>
>
>Will change to u8.
>
>>
>> >
>> > struct vsock_skb_cb {
>> > unsigned int src_cid;
>> >diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>> >index ab08cd81720e..f83b655fdbe9 100644
>> >--- a/net/vmw_vsock/af_vsock.c
>> >+++ b/net/vmw_vsock/af_vsock.c
>> >@@ -487,7 +487,7 @@ vsock_connectible_lookup_transport(unsigned int cid, __u8 flags)
>> > return transport;
>> > }
>> >
>> >-static const struct vsock_transport *
>> >+const struct vsock_transport *
>> > vsock_dgram_lookup_transport(unsigned int cid, __u8 flags)
>> > {
>> > const struct vsock_transport *transport;
>> >diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
>> >index a1c76836d798..46cd1807f8e3 100644
>> >--- a/net/vmw_vsock/virtio_transport_common.c
>> >+++ b/net/vmw_vsock/virtio_transport_common.c
>> >@@ -1040,13 +1040,98 @@ int virtio_transport_shutdown(struct vsock_sock *vsk, int mode)
>> > }
>> > EXPORT_SYMBOL_GPL(virtio_transport_shutdown);
>> >
>> >+static int virtio_transport_dgram_send_pkt_info(struct vsock_sock *vsk,
>> >+ struct virtio_vsock_pkt_info *info)
>> >+{
>> >+ u32 src_cid, src_port, dst_cid, dst_port;
>> >+ const struct vsock_transport *transport;
>> >+ const struct virtio_transport *t_ops;
>> >+ struct sock *sk = sk_vsock(vsk);
>> >+ struct virtio_vsock_hdr *hdr;
>> >+ struct sk_buff *skb;
>> >+ void *payload;
>> >+ int noblock = 0;
>> >+ int err;
>> >+
>> >+ info->type = virtio_transport_get_type(sk_vsock(vsk));
>> >+
>> >+ if (info->pkt_len > VIRTIO_VSOCK_MAX_PKT_BUF_SIZE)
>> >+ return -EMSGSIZE;
>> >+
>> >+ transport = vsock_dgram_lookup_transport(info->remote_cid, info->remote_flags);
>>
>> Can `transport` be null?
>>
>> I don't understand why we are calling vsock_dgram_lookup_transport()
>> again. Didn't we already do that in vsock_dgram_sendmsg()?
>>
>
>transport should be valid here sin)e we null-checked it in
>vsock_dgram_sendmsg(). The reason vsock_dgram_lookup_transport() is
>called again here is we don't have the transport when we called into
>transport->dgram_enqueue(). I can also instead add transport to the
>argument of dgram_enqueue() to eliminate this redundant lookup.
Yes, I would absolutely eliminate this double lookup.
You can add either a parameter, or define the callback in each transport
and internally use the statically allocated transport in each.
For example for vhost/vsock.c:
static int vhost_transport_dgram_enqueue(....) {
return virtio_transport_dgram_enqueue(&vhost_transport.transport,
...)
}
In virtio_transport_recv_pkt() we already do something similar.
>
>> Also should we add a comment mentioning that we can't use
>> virtio_transport_get_ops()? IIUC becuase the vsk can be not assigned
>> to a specific transport, right?
>>
>
>Correct. For virtio dgram socket, transport is not assigned unless
>vsock_dgram_connect() is called. I will add a comment here explaining
>this.
Thanks,
Stefano
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