From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 188E7C25B08 for ; Thu, 18 Aug 2022 03:17:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243063AbiHRDRH (ORCPT ); Wed, 17 Aug 2022 23:17:07 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54478 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242979AbiHRDRF (ORCPT ); Wed, 17 Aug 2022 23:17:05 -0400 Received: from smtp236.sjtu.edu.cn (smtp236.sjtu.edu.cn [202.120.2.236]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6349AA831D; Wed, 17 Aug 2022 20:17:02 -0700 (PDT) Received: from mta90.sjtu.edu.cn (unknown [10.118.0.90]) by smtp236.sjtu.edu.cn (Postfix) with ESMTPS id 07BE91008B389; Thu, 18 Aug 2022 11:16:59 +0800 (CST) Received: from localhost (localhost.localdomain [127.0.0.1]) by mta90.sjtu.edu.cn (Postfix) with ESMTP id D920F37C894; Thu, 18 Aug 2022 11:16:59 +0800 (CST) X-Virus-Scanned: amavisd-new at Received: from mta90.sjtu.edu.cn ([127.0.0.1]) by localhost (mta90.sjtu.edu.cn [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id g2F2qLtILvBE; Thu, 18 Aug 2022 11:16:59 +0800 (CST) Received: from mstore105.sjtu.edu.cn (mstore101.sjtu.edu.cn [10.118.0.105]) by mta90.sjtu.edu.cn (Postfix) with ESMTP id A3DBD37C893; Thu, 18 Aug 2022 11:16:59 +0800 (CST) Date: Thu, 18 Aug 2022 11:16:59 +0800 (CST) From: Guo Zhi To: Xuan Zhuo Cc: netdev , linux-kernel , kvm list , virtualization , eperezma , jasowang , sgarzare , Michael Tsirkin Message-ID: <1091620326.8333566.1660792619533.JavaMail.zimbra@sjtu.edu.cn> In-Reply-To: <1660792318.4436166-3-xuanzhuo@linux.alibaba.com> References: <20220817135718.2553-1-qtxuning1999@sjtu.edu.cn> <20220817135718.2553-7-qtxuning1999@sjtu.edu.cn> <1660792318.4436166-3-xuanzhuo@linux.alibaba.com> Subject: Re: [RFC v2 6/7] virtio: in order support for virtio_ring MIME-Version: 1.0 Content-Type: text/plain; charset=GB2312 Content-Transfer-Encoding: 7bit X-Originating-IP: [36.148.65.198] X-Mailer: Zimbra 8.8.15_GA_4308 (ZimbraWebClient - GC103 (Mac)/8.8.15_GA_3928) Thread-Topic: virtio: in order support for virtio_ring Thread-Index: V9KFug4AVD63FIQF+R2n8Bnz0889Jw== Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org ----- Original Message ----- > From: "Xuan Zhuo" > To: "Guo Zhi" > Cc: "netdev" , "linux-kernel" , "kvm list" , > "virtualization" , "Guo Zhi" , "eperezma" > , "jasowang" , "sgarzare" , "Michael Tsirkin" > > Sent: Thursday, August 18, 2022 11:11:58 AM > Subject: Re: [RFC v2 6/7] virtio: in order support for virtio_ring > On Wed, 17 Aug 2022 21:57:17 +0800, Guo Zhi wrote: >> If in order feature negotiated, we can skip the used ring to get >> buffer's desc id sequentially. >> >> Signed-off-by: Guo Zhi >> --- >> drivers/virtio/virtio_ring.c | 53 ++++++++++++++++++++++++++++++------ >> 1 file changed, 45 insertions(+), 8 deletions(-) >> >> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c >> index 1c1b3fa376a2..143184ebb5a1 100644 >> --- a/drivers/virtio/virtio_ring.c >> +++ b/drivers/virtio/virtio_ring.c >> @@ -144,6 +144,9 @@ struct vring_virtqueue { >> /* DMA address and size information */ >> dma_addr_t queue_dma_addr; >> size_t queue_size_in_bytes; >> + >> + /* In order feature batch begin here */ >> + u16 next_desc_begin; >> } split; >> >> /* Available for packed ring */ >> @@ -702,8 +705,13 @@ static void detach_buf_split(struct vring_virtqueue *vq, >> unsigned int head, >> } >> >> vring_unmap_one_split(vq, i); >> - vq->split.desc_extra[i].next = vq->free_head; >> - vq->free_head = head; >> + /* In order feature use desc in order, >> + * that means, the next desc will always be free >> + */ >> + if (!virtio_has_feature(vq->vq.vdev, VIRTIO_F_IN_ORDER)) { > > Call virtio_has_feature() here is not good. > > Thanks. > Maybe I can use a variable like vq->indiret? Thanks. >> + vq->split.desc_extra[i].next = vq->free_head; >> + vq->free_head = head; >> + } >> >> /* Plus final descriptor */ >> vq->vq.num_free++; >> @@ -745,7 +753,7 @@ static void *virtqueue_get_buf_ctx_split(struct virtqueue >> *_vq, >> { >> struct vring_virtqueue *vq = to_vvq(_vq); >> void *ret; >> - unsigned int i; >> + unsigned int i, j; >> u16 last_used; >> >> START_USE(vq); >> @@ -764,11 +772,38 @@ static void *virtqueue_get_buf_ctx_split(struct virtqueue >> *_vq, >> /* Only get used array entries after they have been exposed by host. */ >> virtio_rmb(vq->weak_barriers); >> >> - last_used = (vq->last_used_idx & (vq->split.vring.num - 1)); >> - i = virtio32_to_cpu(_vq->vdev, >> - vq->split.vring.used->ring[last_used].id); >> - *len = virtio32_to_cpu(_vq->vdev, >> - vq->split.vring.used->ring[last_used].len); >> + if (virtio_has_feature(_vq->vdev, VIRTIO_F_IN_ORDER)) { >> + /* Skip used ring and get used desc in order*/ >> + i = vq->split.next_desc_begin; >> + j = i; >> + /* Indirect only takes one descriptor in descriptor table */ >> + while (!vq->indirect && (vq->split.desc_extra[j].flags & VRING_DESC_F_NEXT)) >> + j = (j + 1) % vq->split.vring.num; >> + /* move to next */ >> + j = (j + 1) % vq->split.vring.num; >> + /* Next buffer will use this descriptor in order */ >> + vq->split.next_desc_begin = j; >> + if (!vq->indirect) { >> + *len = vq->split.desc_extra[i].len; >> + } else { >> + struct vring_desc *indir_desc = >> + vq->split.desc_state[i].indir_desc; >> + u32 indir_num = vq->split.desc_extra[i].len, buffer_len = 0; >> + >> + if (indir_desc) { >> + for (j = 0; j < indir_num / sizeof(struct vring_desc); j++) >> + buffer_len += indir_desc[j].len; >> + } >> + >> + *len = buffer_len; >> + } >> + } else { >> + last_used = (vq->last_used_idx & (vq->split.vring.num - 1)); >> + i = virtio32_to_cpu(_vq->vdev, >> + vq->split.vring.used->ring[last_used].id); >> + *len = virtio32_to_cpu(_vq->vdev, >> + vq->split.vring.used->ring[last_used].len); >> + } >> >> if (unlikely(i >= vq->split.vring.num)) { >> BAD_RING(vq, "id %u out of range\n", i); >> @@ -2236,6 +2271,8 @@ struct virtqueue *__vring_new_virtqueue(unsigned int >> index, >> vq->split.avail_flags_shadow = 0; >> vq->split.avail_idx_shadow = 0; >> >> + vq->split.next_desc_begin = 0; >> + >> /* No callback? Tell other side not to bother us. */ >> if (!callback) { >> vq->split.avail_flags_shadow |= VRING_AVAIL_F_NO_INTERRUPT; >> -- >> 2.17.1 >>