linux-kernel - Re: [PATCH net-next v5 3/6] vhost/vsock: support MSG

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Message-ID: <20210903125132.fpuwfij6ggsg4wuf@steredhat>
Date:   Fri, 3 Sep 2021 14:51:32 +0200
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     Arseny Krasnov <arseny.krasnov@...persky.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>,
        Colin Ian King <colin.king@...onical.com>,
        Norbert Slusarek <nslusarek@....net>,
        Andra Paraschiv <andraprs@...zon.com>, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, stsp2@...dex.ru, oxffffaa@...il.com
Subject: Re: [PATCH net-next v5 3/6] vhost/vsock: support MSG_EOR bit
 processing

On Fri, Sep 03, 2021 at 03:32:35PM +0300, Arseny Krasnov wrote:
>'MSG_EOR' handling has similar logic as 'MSG_EOM' - if bit present
>in packet's header, reset it to 0. Then restore it back if packet
>processing wasn't completed. Instead of bool variable for each
>flag, bit mask variable was added: it has logical OR of 'MSG_EOR'
>and 'MSG_EOM' if needed, to restore flags, this variable is ORed
>with flags field of packet.
>
>Signed-off-by: Arseny Krasnov <arseny.krasnov@...persky.com>
>---
> drivers/vhost/vsock.c | 22 +++++++++++++---------
> 1 file changed, 13 insertions(+), 9 deletions(-)
>
>diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
>index feaf650affbe..938aefbc75ec 100644
>--- a/drivers/vhost/vsock.c
>+++ b/drivers/vhost/vsock.c
>@@ -114,7 +114,7 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
> 		size_t nbytes;
> 		size_t iov_len, payload_len;
> 		int head;
>-		bool restore_flag = false;
>+		u32 flags_to_restore = 0;
>
> 		spin_lock_bh(&vsock->send_pkt_list_lock);
> 		if (list_empty(&vsock->send_pkt_list)) {
>@@ -179,15 +179,20 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
> 			 * created dynamically and are initialized with header
> 			 * of current packet(except length). But in case of
> 			 * SOCK_SEQPACKET, we also must clear message delimeter
>-			 * bit(VIRTIO_VSOCK_SEQ_EOM). Otherwise, instead of one
>-			 * packet with delimeter(which marks end of message),
>-			 * there will be sequence of packets with delimeter
>-			 * bit set. After initialized header will be copied to
>-			 * rx buffer, this bit will be restored.
>+			 * bit (VIRTIO_VSOCK_SEQ_EOM) and MSG_EOR bit
>+			 * (VIRTIO_VSOCK_SEQ_EOR) if set. Otherwise,
>+			 * there will be sequence of packets with these
>+			 * bits set. After initialized header will be copied to
>+			 * rx buffer, these required bits will be restored.
> 			 */
> 			if (le32_to_cpu(pkt->hdr.flags) & VIRTIO_VSOCK_SEQ_EOM) {
> 				pkt->hdr.flags &= ~cpu_to_le32(VIRTIO_VSOCK_SEQ_EOM);
>-				restore_flag = true;
>+				flags_to_restore |= VIRTIO_VSOCK_SEQ_EOM;
>+
>+				if (le32_to_cpu(pkt->hdr.flags) & VIRTIO_VSOCK_SEQ_EOR) {
>+					pkt->hdr.flags &= ~cpu_to_le32(VIRTIO_VSOCK_SEQ_EOR);
>+					flags_to_restore |= VIRTIO_VSOCK_SEQ_EOR;
>+				}
> 			}
> 		}
>
>@@ -224,8 +229,7 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
> 		 * to send it with the next available buffer.
> 		 */
> 		if (pkt->off < pkt->len) {
>-			if (restore_flag)
>-				pkt->hdr.flags |= cpu_to_le32(VIRTIO_VSOCK_SEQ_EOM);
>+			pkt->hdr.flags |= cpu_to_le32(flags_to_restore);
>
> 			/* We are queueing the same virtio_vsock_pkt to 
> 			handle
> 			 * the remaining bytes, and we want to deliver it
>-- 
>2.25.1
>

Reviewed-by: Stefano Garzarella <sgarzare@...hat.com>