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Mon, 20 Feb 2023 04:12:58 -0800 (PST) X-Google-Smtp-Source: AK7set/hobYSeobF6Lg+xz9eZkKUsoGc02UN2QKzyvpPGkTIB3OJOC9Yk3raH+HfIricR4oNXt54Qg== X-Received: by 2002:adf:ef47:0:b0:2c5:9ed8:7c74 with SMTP id c7-20020adfef47000000b002c59ed87c74mr626700wrp.19.1676895178289; Mon, 20 Feb 2023 04:12:58 -0800 (PST) Received: from redhat.com ([2.52.5.34]) by smtp.gmail.com with ESMTPSA id s5-20020adfeb05000000b002c54c0a5aa9sm12289734wrn.74.2023.02.20.04.12.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 20 Feb 2023 04:12:57 -0800 (PST) Date: Mon, 20 Feb 2023 07:12:54 -0500 From: "Michael S. Tsirkin" To: Jason Wang Subject: Re: [PATCH vhost 01/10] virtio_ring: split: refactor virtqueue_add_split() for premapped Message-ID: <20230220071202-mutt-send-email-mst@kernel.org> References: <20230214072704.126660-1-xuanzhuo@linux.alibaba.com> <20230214072704.126660-2-xuanzhuo@linux.alibaba.com> MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline Cc: virtualization@lists.linux-foundation.org X-BeenThere: virtualization@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Linux virtualization List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" On Mon, Feb 20, 2023 at 01:37:37PM +0800, Jason Wang wrote: > On Tue, Feb 14, 2023 at 3:27 PM Xuan Zhuo wrote: > > > > DMA-related logic is separated from the virtqueue_add_split to prepare > > for subsequent support for premapped. > > The patch seems to do more than what is described here. > > To simplify reviewers, I'd suggest to split this patch into three: > > 1) virtqueue_add_split_prepare() (could we have a better name?) > 2) virtqueue_map_sgs() > 3) virtqueue_add_split_vring() > > (Or only factor DMA parts out, I haven't gone through the reset of the patches) > > Thanks > It's pretty small, even split is not mandatary imho. But definitely please do document what is done fully. > > > > Signed-off-by: Xuan Zhuo > > --- > > drivers/virtio/virtio_ring.c | 219 ++++++++++++++++++++++++----------- > > 1 file changed, 152 insertions(+), 67 deletions(-) > > > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > > index 41144b5246a8..560ee30d942c 100644 > > --- a/drivers/virtio/virtio_ring.c > > +++ b/drivers/virtio/virtio_ring.c > > @@ -520,29 +520,83 @@ static inline unsigned int virtqueue_add_desc_split(struct virtqueue *vq, > > return next; > > } > > > > -static inline int virtqueue_add_split(struct virtqueue *_vq, > > - struct scatterlist *sgs[], > > - unsigned int total_sg, > > - unsigned int out_sgs, > > - unsigned int in_sgs, > > - void *data, > > - void *ctx, > > - gfp_t gfp) > > +static int virtqueue_map_sgs(struct vring_virtqueue *vq, > > + struct scatterlist *sgs[], > > + unsigned int total_sg, > > + unsigned int out_sgs, > > + unsigned int in_sgs) > > { > > - struct vring_virtqueue *vq = to_vvq(_vq); > > struct scatterlist *sg; > > - struct vring_desc *desc; > > - unsigned int i, n, avail, descs_used, prev, err_idx; > > - int head; > > - bool indirect; > > + unsigned int n; > > > > - START_USE(vq); > > + for (n = 0; n < out_sgs; n++) { > > + for (sg = sgs[n]; sg; sg = sg_next(sg)) { > > + dma_addr_t addr = vring_map_one_sg(vq, sg, DMA_TO_DEVICE); > > + > > + if (vring_mapping_error(vq, addr)) > > + return -ENOMEM; > > + > > + sg->dma_address = addr; > > + } > > + } > > + for (; n < (out_sgs + in_sgs); n++) { > > + for (sg = sgs[n]; sg; sg = sg_next(sg)) { > > + dma_addr_t addr = vring_map_one_sg(vq, sg, DMA_FROM_DEVICE); > > + > > + if (vring_mapping_error(vq, addr)) > > + return -ENOMEM; > > + > > + sg->dma_address = addr; > > + } > > + } > > + > > + return 0; > > +} > > + > > +static void virtqueue_unmap_sgs(struct vring_virtqueue *vq, > > + struct scatterlist *sgs[], > > + unsigned int total_sg, > > + unsigned int out_sgs, > > + unsigned int in_sgs) > > +{ > > + struct scatterlist *sg; > > + unsigned int n; > > + > > + for (n = 0; n < out_sgs; n++) { > > + for (sg = sgs[n]; sg; sg = sg_next(sg)) { > > + if (!sg->dma_address) > > + return; > > + > > + dma_unmap_single(vring_dma_dev(vq), sg->dma_address, > > + sg->length, DMA_TO_DEVICE); > > + } > > + } > > + for (; n < (out_sgs + in_sgs); n++) { > > + for (sg = sgs[n]; sg; sg = sg_next(sg)) { > > + if (!sg->dma_address) > > + return; > > + > > + dma_unmap_single(vring_dma_dev(vq), sg->dma_address, > > + sg->length, DMA_FROM_DEVICE); > > + } > > + } > > +} > > + > > +static inline int virtqueue_add_split_prepare(struct vring_virtqueue *vq, > > + unsigned int total_sg, > > + unsigned int out_sgs, > > + void *data, > > + void *ctx, > > + gfp_t gfp, > > + struct vring_desc **pdesc) > > +{ > > + struct vring_desc *desc; > > + unsigned int descs_used; > > > > BUG_ON(data == NULL); > > BUG_ON(ctx && vq->indirect); > > > > if (unlikely(vq->broken)) { > > - END_USE(vq); > > return -EIO; > > } > > > > @@ -550,27 +604,17 @@ static inline int virtqueue_add_split(struct virtqueue *_vq, > > > > BUG_ON(total_sg == 0); > > > > - head = vq->free_head; > > - > > if (virtqueue_use_indirect(vq, total_sg)) > > - desc = alloc_indirect_split(_vq, total_sg, gfp); > > + desc = alloc_indirect_split(&vq->vq, total_sg, gfp); > > else { > > desc = NULL; > > WARN_ON_ONCE(total_sg > vq->split.vring.num && !vq->indirect); > > } > > > > - if (desc) { > > - /* Use a single buffer which doesn't continue */ > > - indirect = true; > > - /* Set up rest to use this indirect table. */ > > - i = 0; > > + if (desc) > > descs_used = 1; > > - } else { > > - indirect = false; > > - desc = vq->split.vring.desc; > > - i = head; > > + else > > descs_used = total_sg; > > - } > > > > if (unlikely(vq->vq.num_free < descs_used)) { > > pr_debug("Can't add buf len %i - avail = %i\n", > > @@ -580,38 +624,64 @@ static inline int virtqueue_add_split(struct virtqueue *_vq, > > * host should service the ring ASAP. */ > > if (out_sgs) > > vq->notify(&vq->vq); > > - if (indirect) > > - kfree(desc); > > - END_USE(vq); > > + kfree(desc); > > return -ENOSPC; > > } > > > > + *pdesc = desc; > > + > > + return 0; > > +} > > + > > +static inline int virtqueue_add_split_vring(struct vring_virtqueue *vq, > > + struct scatterlist *sgs[], > > + unsigned int total_sg, > > + unsigned int out_sgs, > > + unsigned int in_sgs, > > + struct vring_desc *desc) > > +{ > > + unsigned int n, i, avail, descs_used, prev; > > + struct virtqueue *_vq = &vq->vq; > > + struct scatterlist *sg; > > + bool indirect; > > + int head; > > + > > + head = vq->free_head; > > + > > + if (desc) { > > + /* Use a single buffer which doesn't continue */ > > + indirect = true; > > + /* Set up rest to use this indirect table. */ > > + i = 0; > > + descs_used = 1; > > + } else { > > + indirect = false; > > + desc = vq->split.vring.desc; > > + i = head; > > + descs_used = total_sg; > > + } > > + > > for (n = 0; n < out_sgs; n++) { > > for (sg = sgs[n]; sg; sg = sg_next(sg)) { > > - dma_addr_t addr = vring_map_one_sg(vq, sg, DMA_TO_DEVICE); > > - if (vring_mapping_error(vq, addr)) > > - goto unmap_release; > > - > > prev = i; > > /* Note that we trust indirect descriptor > > * table since it use stream DMA mapping. > > */ > > - i = virtqueue_add_desc_split(_vq, desc, i, addr, sg->length, > > + i = virtqueue_add_desc_split(_vq, desc, i, > > + sg->dma_address, > > + sg->length, > > VRING_DESC_F_NEXT, > > indirect); > > } > > } > > for (; n < (out_sgs + in_sgs); n++) { > > for (sg = sgs[n]; sg; sg = sg_next(sg)) { > > - dma_addr_t addr = vring_map_one_sg(vq, sg, DMA_FROM_DEVICE); > > - if (vring_mapping_error(vq, addr)) > > - goto unmap_release; > > - > > prev = i; > > /* Note that we trust indirect descriptor > > * table since it use stream DMA mapping. > > */ > > - i = virtqueue_add_desc_split(_vq, desc, i, addr, > > + i = virtqueue_add_desc_split(_vq, desc, i, > > + sg->dma_address, > > sg->length, > > VRING_DESC_F_NEXT | > > VRING_DESC_F_WRITE, > > @@ -630,7 +700,7 @@ static inline int virtqueue_add_split(struct virtqueue *_vq, > > vq, desc, total_sg * sizeof(struct vring_desc), > > DMA_TO_DEVICE); > > if (vring_mapping_error(vq, addr)) > > - goto unmap_release; > > + return -ENOMEM; > > > > virtqueue_add_desc_split(_vq, vq->split.vring.desc, > > head, addr, > > @@ -648,13 +718,6 @@ static inline int virtqueue_add_split(struct virtqueue *_vq, > > else > > vq->free_head = i; > > > > - /* Store token and indirect buffer state. */ > > - vq->split.desc_state[head].data = data; > > - if (indirect) > > - vq->split.desc_state[head].indir_desc = desc; > > - else > > - vq->split.desc_state[head].indir_desc = ctx; > > - > > /* Put entry in available array (but don't update avail->idx until they > > * do sync). */ > > avail = vq->split.avail_idx_shadow & (vq->split.vring.num - 1); > > @@ -677,30 +740,52 @@ static inline int virtqueue_add_split(struct virtqueue *_vq, > > virtqueue_kick(_vq); > > > > return 0; > > +} > > > > -unmap_release: > > - err_idx = i; > > +static inline int virtqueue_add_split(struct virtqueue *_vq, > > + struct scatterlist *sgs[], > > + unsigned int total_sg, > > + unsigned int out_sgs, > > + unsigned int in_sgs, > > + void *data, > > + void *ctx, > > + gfp_t gfp) > > +{ > > + struct vring_virtqueue *vq = to_vvq(_vq); > > + struct vring_desc *desc; > > + int head; > > + int err; > > > > - if (indirect) > > - i = 0; > > - else > > - i = head; > > + START_USE(vq); > > > > - for (n = 0; n < total_sg; n++) { > > - if (i == err_idx) > > - break; > > - if (indirect) { > > - vring_unmap_one_split_indirect(vq, &desc[i]); > > - i = virtio16_to_cpu(_vq->vdev, desc[i].next); > > - } else > > - i = vring_unmap_one_split(vq, i); > > - } > > + /* check vq state and try to alloc desc for indirect. */ > > + err = virtqueue_add_split_prepare(vq, total_sg, out_sgs, data, ctx, gfp, &desc); > > + if (err) > > + goto end; > > > > - if (indirect) > > - kfree(desc); > > + err = virtqueue_map_sgs(vq, sgs, total_sg, out_sgs, in_sgs); > > + if (err) > > + goto err; > > > > + head = vq->free_head; > > + err = virtqueue_add_split_vring(vq, sgs, total_sg, out_sgs, in_sgs, desc); > > + if (err) > > + goto err; > > + > > + /* Store token and indirect buffer state. */ > > + vq->split.desc_state[head].data = data; > > + vq->split.desc_state[head].indir_desc = desc ? desc : ctx; > > + > > + goto end; > > + > > +err: > > + virtqueue_unmap_sgs(vq, sgs, total_sg, out_sgs, in_sgs); > > + > > + kfree(desc); > > + > > +end: > > END_USE(vq); > > - return -ENOMEM; > > + return err; > > } > > > > static bool virtqueue_kick_prepare_split(struct virtqueue *_vq) > > -- > > 2.32.0.3.g01195cf9f > > _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization