From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 57C0A245020 for ; Wed, 28 May 2025 06:43:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748414623; cv=none; b=fZqWdj8NuC4fqLCt7MVGEFva5pNH80aTVU8KHFtiuhGeLlXgmOWU5R4PJgnRAk7tilcwiUeoAs9BRwU3hmZ723aWjO1m8dLbtYA7sXj3CJmV2ehjq40SnAT58GyjZMNhpstRWzBQtas4OZZm49wJbbR3SnZ0fkphHnP3jFCYbZk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748414623; c=relaxed/simple; bh=kYIqNdkOmmWfjWSfE+ekXjKoiJ0qClEBC5ouYkDt8g4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=c4we6rmuL25kzmn16M68+1GKwkJsaXAJaSOt21JVwlDIYRCIayBBWlmtJXJ8JbxzWwGrKUrLOuJyinxTLPrTUlYyqruGs50n/ceSJWoghJjVXPGNV4UN5l2gR3dj6T61K6cABecIdXvJj41kF475mmuuBChoc9WvuPRtjnEElng= 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=FOXnqzvZ; arc=none smtp.client-ip=170.10.129.124 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="FOXnqzvZ" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1748414621; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=813OkOWRMLxQ6cmfOaG7x0vfbwOfMBKmXewVWgcnVS4=; b=FOXnqzvZPxU0q801ATPuhkEggIO86ouFRG6GQ3PECYXo0XE6NXqu9RhSrwPj/fkBnRwztQ 0s3Ov/QDprUtVdhkfXfmVJK2SRv37VKO2rFBDe8I8NfxcorXlIgNys75q4JT/i5q4S7Y8x PRD5g4dFJRBTEz2i6hx86sVfKc6UMgE= Received: from mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-145-HvF4vHsdMYWuxnHXeBGxMQ-1; Wed, 28 May 2025 02:43:39 -0400 X-MC-Unique: HvF4vHsdMYWuxnHXeBGxMQ-1 X-Mimecast-MFC-AGG-ID: HvF4vHsdMYWuxnHXeBGxMQ_1748414619 Received: from mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.15]) (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-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id D9821195608C; Wed, 28 May 2025 06:43:38 +0000 (UTC) Received: from localhost.localdomain (unknown [10.72.112.248]) by mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 9C86A1956095; Wed, 28 May 2025 06:43:35 +0000 (UTC) From: Jason Wang To: mst@redhat.com, jasowang@redhat.com Cc: xuanzhuo@linux.alibaba.com, eperezma@redhat.com, virtualization@lists.linux.dev, linux-kernel@vger.kernel.org Subject: [PATCH V2 14/19] virtio_ring: determine descriptor flags at one time Date: Wed, 28 May 2025 14:42:29 +0800 Message-ID: <20250528064234.12228-15-jasowang@redhat.com> In-Reply-To: <20250528064234.12228-1-jasowang@redhat.com> References: <20250528064234.12228-1-jasowang@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.0 on 10.30.177.15 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. Reviewed-by: Xuan Zhuo Signed-off-by: Jason Wang --- drivers/virtio/virtio_ring.c | 25 +++++++++++++------------ 1 file changed, 13 insertions(+), 12 deletions(-) diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index af32d1a1a1db..d5e4d4cd2487 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_virtqueue *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, c, avail, descs_used, err_idx; int head; bool indirect; @@ -626,46 +626,47 @@ static inline int virtqueue_add_split(struct vring_virtqueue *vq, return -ENOSPC; } + c = 0; for (n = 0; n < out_sgs; n++) { + sg = sgs[n]; for (sg = sgs[n]; sg; sg = sg_next(sg)) { dma_addr_t addr; u32 len; + u16 flags = 0; if (vring_map_one_sg(vq, sg, DMA_TO_DEVICE, &addr, &len, premapped)) goto unmap_release; - prev = i; + if (++c != total_sg) + flags = VRING_DESC_F_NEXT; + /* Note that we trust indirect descriptor * table since it use stream DMA mapping. */ i = virtqueue_add_desc_split(vq, desc, extra, i, addr, len, - VRING_DESC_F_NEXT, + flags, premapped); } } for (; n < (out_sgs + in_sgs); n++) { for (sg = sgs[n]; sg; sg = sg_next(sg)) { + u16 flags = VRING_DESC_F_WRITE; dma_addr_t addr; u32 len; if (vring_map_one_sg(vq, sg, DMA_FROM_DEVICE, &addr, &len, premapped)) goto unmap_release; - prev = i; + if (++c != total_sg) + flags |= VRING_DESC_F_NEXT; + /* Note that we trust indirect descriptor * table since it use stream DMA mapping. */ i = virtqueue_add_desc_split(vq, desc, extra, i, addr, len, - VRING_DESC_F_NEXT | - VRING_DESC_F_WRITE, - premapped); + flags, premapped); } } - /* Last one doesn't continue. */ - desc[prev].flags &= 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 &= - ~VRING_DESC_F_NEXT; if (indirect) { /* Now that the indirect table is filled in, map it. */ -- 2.31.1