From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (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 40E15107B1 for ; Fri, 2 Jun 2023 11:40:55 +0000 (UTC) Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 755B4198 for ; Fri, 2 Jun 2023 04:40:54 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1685706053; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=VxnskxVO8AXS1VjjPX0Qehr8afrCv+Lu5/PB3QTgDqI=; b=YLVcfy46i1j3Uf5FPOWDTklHTCzy5OSNxmH5XgBnS/UyyhIYNLbR8lEJVPKMPXvYmgFsND gUrlSLqZXOBG9YdI8S7kAK1/2PHyB/W9UP2xHhhvz+J8wFGt130j8id2y5BZbpoolzJ7Fk vALoiMJ9j2GGcmuMAUFIwi0+U9dqiNs= Received: from mail-wm1-f69.google.com (mail-wm1-f69.google.com [209.85.128.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-52-y5RjbxrtNzasugmhM3E2Gw-1; Fri, 02 Jun 2023 07:40:52 -0400 X-MC-Unique: y5RjbxrtNzasugmhM3E2Gw-1 Received: by mail-wm1-f69.google.com with SMTP id 5b1f17b1804b1-3f725f64b46so11410605e9.1 for ; Fri, 02 Jun 2023 04:40:52 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1685706051; x=1688298051; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=VxnskxVO8AXS1VjjPX0Qehr8afrCv+Lu5/PB3QTgDqI=; b=eJE9coshiLgjXkcy8QwRHZ36KSaY6tuf/a+hYPHDWIs1gaPwxFqxnUbkvPlJcMICUN EVdqYU8nbZfaAGxNdA8JZVWc+UO73+sc68ghmDHPvMu6+fYBdYlOxtTBNNgIvguCUfF8 Vu8kjpDcG3s6wzXfF/wTvu34N/yPIQUFdZ4RZ6GWym6/5/cxc7i3ku/KiBKuv1yXwo7p fC1unEvieJGg649fDHRabnYHx5q96ZYP1CotZTqAsVXF5Pyyv0X2BMHPwcWgKCgyHYzT +f4+xv2ES7O+j10yQxMgWYrOQf6IDvCqZi86n06nE+z1nhTAMWPwBdWzBMXqU1EKkIc0 TvaA== X-Gm-Message-State: AC+VfDxzMkQkEV7EQ7h4or+ZDFkDIKwboo8QUYS91W4iNyg0YpLZDo3h 0m91ZjgbtCMC4g2/XPxHMeVrB143cQ9RedZRFUjokHF3wEEona0XFAMNSkNaiMwHE/AP60QAXIF OHJoshMyaAwMUVTJ2 X-Received: by 2002:a7b:c40e:0:b0:3f6:692:5607 with SMTP id k14-20020a7bc40e000000b003f606925607mr1576908wmi.40.1685706051318; Fri, 02 Jun 2023 04:40:51 -0700 (PDT) X-Google-Smtp-Source: ACHHUZ5kq+QX6iZImB+mIj7tvU+uwhorlCzeq6kS3V5YFUILtTH1qTcWoVOSLmlm1M3rGXDIz4wULg== X-Received: by 2002:a7b:c40e:0:b0:3f6:692:5607 with SMTP id k14-20020a7bc40e000000b003f606925607mr1576894wmi.40.1685706050946; Fri, 02 Jun 2023 04:40:50 -0700 (PDT) Received: from redhat.com ([2.55.4.169]) by smtp.gmail.com with ESMTPSA id u8-20020a7bc048000000b003f4b6bcbd8bsm1688452wmc.31.2023.06.02.04.40.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 02 Jun 2023 04:40:50 -0700 (PDT) Date: Fri, 2 Jun 2023 07:40:46 -0400 From: "Michael S. Tsirkin" To: Xuan Zhuo Cc: virtualization@lists.linux-foundation.org, Jason Wang , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Alexei Starovoitov , Daniel Borkmann , Jesper Dangaard Brouer , John Fastabend , netdev@vger.kernel.org, bpf@vger.kernel.org Subject: Re: [PATCH vhost v10 06/10] virtio_ring: packed-detach: support return dma info to driver Message-ID: <20230602073827-mutt-send-email-mst@kernel.org> References: <20230602092206.50108-1-xuanzhuo@linux.alibaba.com> <20230602092206.50108-7-xuanzhuo@linux.alibaba.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230602092206.50108-7-xuanzhuo@linux.alibaba.com> X-Spam-Status: No, score=-2.3 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, SPF_HELO_NONE,SPF_NONE,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net On Fri, Jun 02, 2023 at 05:22:02PM +0800, Xuan Zhuo wrote: > Under the premapped mode, the driver needs to unmap the DMA address > after receiving the buffer. The virtio core records the DMA address, > so the driver needs a way to get the dma info from the virtio core. > > A straightforward approach is to pass an array to the virtio core when > calling virtqueue_get_buf(). However, it is not feasible when there are > multiple DMA addresses in the descriptor chain, and the array size is > unknown. > > To solve this problem, a helper be introduced. After calling > virtqueue_get_buf(), the driver can call the helper to > retrieve a dma info. If the helper function returns -EAGAIN, it means > that there are more DMA addresses to be processed, and the driver should > call the helper function again. Please, keep error codes for when an actual error occurs. A common pattern would be: <0 - error 0 - success, done >0 - success, more to do > To keep track of the current position in > the chain, a cursor must be passed to the helper function, which is > initialized by virtqueue_get_buf(). > > Some processes are done inside this helper, so this helper MUST be > called under the premapped mode. > > Signed-off-by: Xuan Zhuo > --- > drivers/virtio/virtio_ring.c | 105 ++++++++++++++++++++++++++++++++--- > include/linux/virtio.h | 9 ++- > 2 files changed, 103 insertions(+), 11 deletions(-) > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > index cdc4349f6066..cbc22daae7e1 100644 > --- a/drivers/virtio/virtio_ring.c > +++ b/drivers/virtio/virtio_ring.c > @@ -1695,8 +1695,85 @@ static bool virtqueue_kick_prepare_packed(struct virtqueue *_vq) > return needs_kick; > } > > +static void detach_cursor_init_packed(struct vring_virtqueue *vq, > + struct virtqueue_detach_cursor *cursor, u16 id) > +{ > + struct vring_desc_state_packed *state = NULL; > + u32 len; > + > + state = &vq->packed.desc_state[id]; > + > + /* Clear data ptr. */ > + state->data = NULL; > + > + vq->packed.desc_extra[state->last].next = vq->free_head; > + vq->free_head = id; > + vq->vq.num_free += state->num; > + > + /* init cursor */ > + cursor->curr = id; > + cursor->done = 0; > + cursor->pos = 0; > + > + if (vq->packed.desc_extra[id].flags & VRING_DESC_F_INDIRECT) { > + len = vq->split.desc_extra[id].len; > + > + cursor->num = len / sizeof(struct vring_packed_desc); > + cursor->indirect = true; > + > + vring_unmap_extra_packed(vq, &vq->packed.desc_extra[id]); > + } else { > + cursor->num = state->num; > + cursor->indirect = false; > + } > +} > + > +static int virtqueue_detach_packed(struct virtqueue *_vq, struct virtqueue_detach_cursor *cursor, > + dma_addr_t *addr, u32 *len, enum dma_data_direction *dir) > +{ > + struct vring_virtqueue *vq = to_vvq(_vq); > + > + if (unlikely(cursor->done)) > + return -EINVAL; > + > + if (!cursor->indirect) { > + struct vring_desc_extra *extra; > + > + extra = &vq->packed.desc_extra[cursor->curr]; > + cursor->curr = extra->next; > + > + *addr = extra->addr; > + *len = extra->len; > + *dir = (extra->flags & VRING_DESC_F_WRITE) ? DMA_FROM_DEVICE : DMA_TO_DEVICE; > + > + if (++cursor->pos == cursor->num) { > + cursor->done = true; > + return 0; > + } > + } else { > + struct vring_packed_desc *indir_desc, *desc; > + u16 flags; > + > + indir_desc = vq->packed.desc_state[cursor->curr].indir_desc; > + desc = &indir_desc[cursor->pos]; > + > + flags = le16_to_cpu(desc->flags); > + *addr = le64_to_cpu(desc->addr); > + *len = le32_to_cpu(desc->len); > + *dir = (flags & VRING_DESC_F_WRITE) ? DMA_FROM_DEVICE : DMA_TO_DEVICE; > + > + if (++cursor->pos == cursor->num) { > + kfree(indir_desc); > + cursor->done = true; > + return 0; > + } > + } > + > + return -EAGAIN; > +} > + > static void detach_buf_packed(struct vring_virtqueue *vq, > - unsigned int id, void **ctx) > + unsigned int id) > { > struct vring_desc_state_packed *state = NULL; > struct vring_packed_desc *desc; > @@ -1736,8 +1813,6 @@ static void detach_buf_packed(struct vring_virtqueue *vq, > } > kfree(desc); > state->indir_desc = NULL; > - } else if (ctx) { > - *ctx = state->indir_desc; > } > } > > @@ -1768,7 +1843,8 @@ static bool more_used_packed(const struct vring_virtqueue *vq) > > static void *virtqueue_get_buf_ctx_packed(struct virtqueue *_vq, > unsigned int *len, > - void **ctx) > + void **ctx, > + struct virtqueue_detach_cursor *cursor) > { > struct vring_virtqueue *vq = to_vvq(_vq); > u16 last_used, id, last_used_idx; > @@ -1808,7 +1884,14 @@ static void *virtqueue_get_buf_ctx_packed(struct virtqueue *_vq, > > /* detach_buf_packed clears data, so grab it now. */ > ret = vq->packed.desc_state[id].data; > - detach_buf_packed(vq, id, ctx); > + > + if (!vq->indirect && ctx) > + *ctx = vq->packed.desc_state[id].indir_desc; > + > + if (vq->premapped) > + detach_cursor_init_packed(vq, cursor, id); > + else > + detach_buf_packed(vq, id); > > last_used += vq->packed.desc_state[id].num; > if (unlikely(last_used >= vq->packed.vring.num)) { > @@ -1960,7 +2043,8 @@ static bool virtqueue_enable_cb_delayed_packed(struct virtqueue *_vq) > return true; > } > > -static void *virtqueue_detach_unused_buf_packed(struct virtqueue *_vq) > +static void *virtqueue_detach_unused_buf_packed(struct virtqueue *_vq, > + struct virtqueue_detach_cursor *cursor) > { > struct vring_virtqueue *vq = to_vvq(_vq); > unsigned int i; > @@ -1973,7 +2057,10 @@ static void *virtqueue_detach_unused_buf_packed(struct virtqueue *_vq) > continue; > /* detach_buf clears data, so grab it now. */ > buf = vq->packed.desc_state[i].data; > - detach_buf_packed(vq, i, NULL); > + if (vq->premapped) > + detach_cursor_init_packed(vq, cursor, i); > + else > + detach_buf_packed(vq, i); > END_USE(vq); > return buf; > } > @@ -2458,7 +2545,7 @@ void *virtqueue_get_buf_ctx(struct virtqueue *_vq, unsigned int *len, > { > struct vring_virtqueue *vq = to_vvq(_vq); > > - return vq->packed_ring ? virtqueue_get_buf_ctx_packed(_vq, len, ctx) : > + return vq->packed_ring ? virtqueue_get_buf_ctx_packed(_vq, len, ctx, NULL) : > virtqueue_get_buf_ctx_split(_vq, len, ctx, NULL); > } > EXPORT_SYMBOL_GPL(virtqueue_get_buf_ctx); > @@ -2590,7 +2677,7 @@ void *virtqueue_detach_unused_buf(struct virtqueue *_vq) > { > struct vring_virtqueue *vq = to_vvq(_vq); > > - return vq->packed_ring ? virtqueue_detach_unused_buf_packed(_vq) : > + return vq->packed_ring ? virtqueue_detach_unused_buf_packed(_vq, NULL) : > virtqueue_detach_unused_buf_split(_vq, NULL); > } > EXPORT_SYMBOL_GPL(virtqueue_detach_unused_buf); > diff --git a/include/linux/virtio.h b/include/linux/virtio.h > index eb4a4e4329aa..7f137c7a9034 100644 > --- a/include/linux/virtio.h > +++ b/include/linux/virtio.h > @@ -43,8 +43,13 @@ struct virtqueue_detach_cursor { > unsigned done:1; > unsigned hole:14; > > - /* for split head */ > - unsigned head:16; > + union { > + /* for split head */ > + unsigned head:16; > + > + /* for packed id */ > + unsigned curr:16; > + }; > unsigned num:16; > unsigned pos:16; > }; > -- > 2.32.0.3.g01195cf9f