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[82.53.135.12]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4606f2cf5d9sm39082850f8f.32.2026.06.16.06.10.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 16 Jun 2026 06:10:13 -0700 (PDT) Date: Tue, 16 Jun 2026 15:09:59 +0200 From: Stefano Garzarella To: Arseniy Krasnov Cc: Stefan Hajnoczi , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , "Michael S. Tsirkin" , Jason Wang , Bobby Eshleman , Xuan Zhuo , Eugenio =?utf-8?B?UMOpcmV6?= , Simon Horman , kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, oxffffaa@gmail.com, rulkc@linuxtesting.org Subject: Re: [PATCH v2] vsock/virtio: rework MSG_ZEROCOPY flag handling Message-ID: References: <20260614174756.170631-1-avkrasnov@rulkc.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20260614174756.170631-1-avkrasnov@rulkc.org> On Sun, Jun 14, 2026 at 08:47:56PM +0300, Arseniy Krasnov wrote: >Logically it was based on TCP implementation, so make further support >easier, rewrite it in the TCP way. Hi Arseniy, and thank you so much for the patch! I’d like to ask you to expand on the message a bit, especially to explain why we’re making this change. In particular, I’d like to better understand whether this is just a cosmetic change or if we’re fixing any issues (and if so, which ones), so we can determine whether this patch should be backported to the stable branches. > >Signed-off-by: Arseniy Krasnov >--- > Changelog v1->v2: > * Rebase on last 'net-next'. Don't need 'skb_zcopy_set()' now - it was > already added. Ah, okay is net-next material, please use the net-next tag (ie. [PATCH net-next v2]). > > net/vmw_vsock/virtio_transport_common.c | 48 ++++++++++++------------- > 1 file changed, 23 insertions(+), 25 deletions(-) > >diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c >index 09475007165b..787524b8cb44 100644 >--- a/net/vmw_vsock/virtio_transport_common.c >+++ b/net/vmw_vsock/virtio_transport_common.c >@@ -328,38 +328,36 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk, > if (pkt_len == 0 && info->op == VIRTIO_VSOCK_OP_RW) > return pkt_len; > >- if (info->msg) { >- /* If zerocopy is not enabled by 'setsockopt()', we behave as >- * there is no MSG_ZEROCOPY flag set. >+ if (info->msg && (info->msg->msg_flags & MSG_ZEROCOPY)) { >+ /* If 'info->msg' is not NULL, this is only VIRTIO_VSOCK_OP_RW. >+ * 'MSG_ZEROCOPY' flag handling here is based on the same flag >+ * handling from 'tcp_sendmsg_locked()'. > */ >- if (!sock_flag(sk_vsock(vsk), SOCK_ZEROCOPY)) >- info->msg->msg_flags &= ~MSG_ZEROCOPY; >+ if (info->msg->msg_ubuf) { >+ uarg = info->msg->msg_ubuf; >+ can_zcopy = virtio_transport_can_zcopy(t_ops, info, pkt_len); >+ } else if (sock_flag(sk_vsock(vsk), SOCK_ZEROCOPY)) { >+ uarg = msg_zerocopy_realloc(sk_vsock(vsk), pkt_len, >+ NULL, false); >+ if (!uarg) { >+ virtio_transport_put_credit(vvs, pkt_len); >+ return -ENOMEM; >+ } > >- if (info->msg->msg_flags & MSG_ZEROCOPY) > can_zcopy = virtio_transport_can_zcopy(t_ops, info, pkt_len); > nit: we can remove this extra blank line. For the rest I can't see anything wrong, but a bit more context in the commit would help me in the review. Thanks, Stefano