netdev - Re: [RFC PATCH v1 3/7] vhost/vsock: support MSG

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Date:   Fri, 6 Aug 2021 09:28:49 +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>,
        Norbert Slusarek <nslusarek@....net>,
        Andra Paraschiv <andraprs@...zon.com>,
        Colin Ian King <colin.king@...onical.com>,
        kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        oxffffaa@...il.com
Subject: Re: [RFC PATCH v1 3/7] vhost/vsock: support MSG_EOR bit processing

On Mon, Jul 26, 2021 at 07:33:38PM +0300, Arseny Krasnov wrote:
>It works in the same way as 'end-of-message' bit: if packet has
>'EOM' bit, also check for 'EOR' bit.
>
>Signed-off-by: Arseny Krasnov <arseny.krasnov@...persky.com>
>---
> drivers/vhost/vsock.c | 12 +++++++++++-
> 1 file changed, 11 insertions(+), 1 deletion(-)
>
>diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
>index 3b55de70ac77..3e2b150f9c6f 100644
>--- a/drivers/vhost/vsock.c
>+++ b/drivers/vhost/vsock.c
>@@ -115,6 +115,7 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
> 		size_t iov_len, payload_len;
> 		int head;
> 		bool restore_msg_eom_flag = false;
>+		bool restore_msg_eor_flag = false;

Since we now have 2 flags to potentially restore, we could use a single
variable (e.g. uint32_t flags_to_restore), initialized to 0.

We can set all the flags we need to restore and then simply put it
in or with the `pkt->hdr.flags` field.

> 		spin_lock_bh(&vsock->send_pkt_list_lock);
> 		if (list_empty(&vsock->send_pkt_list)) {
>@@ -188,6 +189,11 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
> 			if (le32_to_cpu(pkt->hdr.flags) & VIRTIO_VSOCK_SEQ_EOM) {
> 				pkt->hdr.flags &= ~cpu_to_le32(VIRTIO_VSOCK_SEQ_EOM);
> 				restore_msg_eom_flag = true;
>+
>+				if (le32_to_cpu(pkt->hdr.flags & VIRTIO_VSOCK_SEQ_EOR)) {
                                                                ^
Here it should be `le32_to_cpu(pkt->hdr.flags) & VIRTIO_VSOCK_SEQ_EOR`

>+					pkt->hdr.flags &= ~cpu_to_le32(VIRTIO_VSOCK_SEQ_EOR);
>+					restore_msg_eor_flag = true;
>+				}
> 			}
> 		}
>
>@@ -224,9 +230,13 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
> 		 * to send it with the next available buffer.
> 		 */
> 		if (pkt->off < pkt->len) {
>-			if (restore_msg_eom_flag)
>+			if (restore_msg_eom_flag) {
> 				pkt->hdr.flags |= cpu_to_le32(VIRTIO_VSOCK_SEQ_EOM);
>
>+				if (restore_msg_eor_flag)
>+					pkt->hdr.flags |= cpu_to_le32(VIRTIO_VSOCK_SEQ_EOR);
>+			}
>+

If we use a single variable, here we can simply do:

			pkt->hdr.flags |= cpu_to_le32(flags_to_restore);

Stefano