From nobody Mon Oct 6 08:24:23 2025 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5460722FAF4 for ; Thu, 24 Jul 2025 06:41:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753339290; cv=none; b=CCv0IySxSH4InJH2C9CpJigSV2G32nwUPySqPnRzABw7wGtWq/ywk+xUqNUzfl2/ybOPvTz9Q0lzkxxbuCY+y1jg9zRqEp2EL6ICOjVVnu6/vneY7HJmWRhalF+lETg3Vw09nj7XG3GEN5HxUKHPfDII0dUdrV2gbziUG8spUqk= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753339290; c=relaxed/simple; bh=CeiTqtpT3BCdJoDDAqMKZFHC7DJJaHTsQtRK8FEcu70=; h=From:To:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=QUJu0DDGDJzrrfK/0NzsFfQKqfxLxYHgIJLjh4XXBvRotfKhtUst1ukET1FuEc2cW0viatUQsguCcCsmvEKgViwmobDWKQQkmjwi9Tp6FYUsP+ZMxEm50iIhDZ5xLr9TGxvTXu12CPBtVYTLYSeLBihe9kmI6BBkYtzxFdTIp9A= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=iY3rW/5c; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="iY3rW/5c" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1753339287; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=qc6FYNQBKIB+acS4K5VrBDZprHD+upxJfELmeFU0+t4=; b=iY3rW/5c82Wp2337cByulnTkQsDUfst76r3OUg0rYDZj6wVEcGnpA4wR5M51ipy1VM9Ws8 i8GOULLxIRz1dOxxW+9bEM4RyOT0Vx7/UHI1+al0zMJ3WSQQdB6TlzdrLVfjRSvT5Rc01K sCViA1/wZiA9gqmVNc7xx9dAN38rQXo= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-14-pKXsCnHKNHu9qGqTFX86ww-1; Thu, 24 Jul 2025 02:41:25 -0400 X-MC-Unique: pKXsCnHKNHu9qGqTFX86ww-1 X-Mimecast-MFC-AGG-ID: pKXsCnHKNHu9qGqTFX86ww_1753339284 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 2ACA91800294; Thu, 24 Jul 2025 06:41:24 +0000 (UTC) Received: from localhost.localdomain (unknown [10.72.112.231]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 070B5180035E; Thu, 24 Jul 2025 06:41:20 +0000 (UTC) From: Jason Wang To: mst@redhat.com, jasowang@redhat.com, xuanzhuo@linux.alibaba.com, eperezma@redhat.com, virtualization@lists.linux.dev, linux-kernel@vger.kernel.org Subject: [PATCH V4 14/19] virtio_ring: determine descriptor flags at one time Date: Thu, 24 Jul 2025 14:40:12 +0800 Message-ID: <20250724064017.26058-15-jasowang@redhat.com> In-Reply-To: <20250724064017.26058-1-jasowang@redhat.com> References: <20250724064017.26058-1-jasowang@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 Let's determine the last descriptor by counting the number of sg. This would be consistent with packed virtqueue implementation and ease the future in-order implementation. Acked-by: Eugenio P=C3=A9rez Reviewed-by: Xuan Zhuo Signed-off-by: Jason Wang --- drivers/virtio/virtio_ring.c | 21 ++++++++------------- 1 file changed, 8 insertions(+), 13 deletions(-) diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index 2f0b14940e05..01bbbcd65417 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -570,7 +570,7 @@ static inline int virtqueue_add_split(struct vring_virt= queue *vq, struct vring_desc_extra *extra; struct scatterlist *sg; struct vring_desc *desc; - unsigned int i, n, avail, descs_used, prev, err_idx; + unsigned int i, n, avail, descs_used, err_idx, c =3D 0; int head; bool indirect; =20 @@ -627,6 +627,7 @@ static inline int virtqueue_add_split(struct vring_virt= queue *vq, } =20 for (n =3D 0; n < out_sgs; n++) { + sg =3D sgs[n]; for (sg =3D sgs[n]; sg; sg =3D sg_next(sg)) { dma_addr_t addr; u32 len; @@ -634,12 +635,12 @@ static inline int virtqueue_add_split(struct vring_vi= rtqueue *vq, if (vring_map_one_sg(vq, sg, DMA_TO_DEVICE, &addr, &len, premapped)) goto unmap_release; =20 - prev =3D i; /* Note that we trust indirect descriptor * table since it use stream DMA mapping. */ i =3D virtqueue_add_desc_split(vq, desc, extra, i, addr, len, - VRING_DESC_F_NEXT, + ++c =3D=3D total_sg ? + 0 : VRING_DESC_F_NEXT, premapped); } } @@ -651,21 +652,15 @@ static inline int virtqueue_add_split(struct vring_vi= rtqueue *vq, if (vring_map_one_sg(vq, sg, DMA_FROM_DEVICE, &addr, &len, premapped)) goto unmap_release; =20 - prev =3D i; /* Note that we trust indirect descriptor * table since it use stream DMA mapping. */ - i =3D virtqueue_add_desc_split(vq, desc, extra, i, addr, len, - VRING_DESC_F_NEXT | - VRING_DESC_F_WRITE, - premapped); + i =3D virtqueue_add_desc_split(vq, desc, extra, + i, addr, len, + (++c =3D=3D total_sg ? 0 : VRING_DESC_F_NEXT) | + VRING_DESC_F_WRITE, premapped); } } - /* Last one doesn't continue. */ - desc[prev].flags &=3D cpu_to_virtio16(vq->vq.vdev, ~VRING_DESC_F_NEXT); - if (!indirect && vring_need_unmap_buffer(vq, &extra[prev])) - vq->split.desc_extra[prev & (vq->split.vring.num - 1)].flags &=3D - ~VRING_DESC_F_NEXT; =20 if (indirect) { /* Now that the indirect table is filled in, map it. */ --=20 2.39.5