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Tsirkin" To: Xuan Zhuo Cc: virtualization@lists.linux.dev, Richard Weinberger , Anton Ivanov , Johannes Berg , Jason Wang , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Hans de Goede , Ilpo =?iso-8859-1?Q?J=E4rvinen?= , Vadim Pasternak , Bjorn Andersson , Mathieu Poirier , Cornelia Huck , Halil Pasic , Eric Farman , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , Alexei Starovoitov , Daniel Borkmann , Jesper Dangaard Brouer , John Fastabend , linux-um@lists.infradead.org, netdev@vger.kernel.org, platform-driver-x86@vger.kernel.org, linux-remoteproc@vger.kernel.org, linux-s390@vger.kernel.org, kvm@vger.kernel.org, bpf@vger.kernel.org Subject: Re: [PATCH vhost v2 19/19] virtio_net: sq support premapped mode Message-ID: <20240226070030-mutt-send-email-mst@kernel.org> References: <20240223082726.52915-1-xuanzhuo@linux.alibaba.com> <20240223082726.52915-20-xuanzhuo@linux.alibaba.com> <20240225032330-mutt-send-email-mst@kernel.org> <1708939451.7601678-3-xuanzhuo@linux.alibaba.com> <20240226063843-mutt-send-email-mst@kernel.org> <1708947680.4503584-3-xuanzhuo@linux.alibaba.com> <20240226065746-mutt-send-email-mst@kernel.org> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: <20240226065746-mutt-send-email-mst@kernel.org> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Mon, Feb 26, 2024 at 07:00:09AM -0500, Michael S. Tsirkin wrote: > On Mon, Feb 26, 2024 at 07:41:20PM +0800, Xuan Zhuo wrote: > > On Mon, 26 Feb 2024 06:39:51 -0500, "Michael S. Tsirkin" wrote: > > > On Mon, Feb 26, 2024 at 05:24:11PM +0800, Xuan Zhuo wrote: > > > > On Sun, 25 Feb 2024 03:38:48 -0500, "Michael S. Tsirkin" wrote: > > > > > On Fri, Feb 23, 2024 at 04:27:26PM +0800, Xuan Zhuo wrote: > > > > > > If the xsk is enabling, the xsk tx will share the send queue. > > > > > > But the xsk requires that the send queue use the premapped mode. > > > > > > So the send queue must support premapped mode. > > > > > > > > > > > > cmd: > > > > > > sh samples/pktgen/pktgen_sample01_simple.sh -i eth0 \ > > > > > > -s 16 -d 10.0.0.128 -m 00:16:3e:2c:c8:2e -n 0 -p 100 > > > > > > CPU: > > > > > > Intel(R) Xeon(R) Platinum 8369B CPU @ 2.70GHz > > > > > > > > > > > > Machine: > > > > > > ecs.g7.2xlarge(Aliyun) > > > > > > > > > > > > before: 1600010.00 > > > > > > after(no-premapped): 1599966.00 > > > > > > after(premapped): 1600014.00 > > > > > > > > > > > > Signed-off-by: Xuan Zhuo > > > > > > --- > > > > > > drivers/net/virtio_net.c | 136 +++++++++++++++++++++++++++++++++++++-- > > > > > > 1 file changed, 132 insertions(+), 4 deletions(-) > > > > > > > > > > > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > > > > > > index 7715bb7032ec..b83ef6afc4fb 100644 > > > > > > --- a/drivers/net/virtio_net.c > > > > > > +++ b/drivers/net/virtio_net.c > > > > > > @@ -146,6 +146,25 @@ struct virtnet_rq_dma { > > > > > > u16 need_sync; > > > > > > }; > > > > > > > > > > > > +struct virtnet_sq_dma { > > > > > > + union { > > > > > > + struct virtnet_sq_dma *next; > > > > > > + void *data; > > > > > > + }; > > > > > > + > > > > > > + u32 num; > > > > > > + > > > > > > + dma_addr_t addr[MAX_SKB_FRAGS + 2]; > > > > > > + u32 len[MAX_SKB_FRAGS + 2]; > > > > > > +}; > > > > > > + > > > > > > +struct virtnet_sq_dma_head { > > > > > > + /* record for kfree */ > > > > > > + void *p; > > > > > > + > > > > > > + struct virtnet_sq_dma *free; > > > > > > +}; > > > > > > + > > > > > > /* Internal representation of a send virtqueue */ > > > > > > struct send_queue { > > > > > > /* Virtqueue associated with this send _queue */ > > > > > > @@ -165,6 +184,8 @@ struct send_queue { > > > > > > > > > > > > /* Record whether sq is in reset state. */ > > > > > > bool reset; > > > > > > + > > > > > > + struct virtnet_sq_dma_head dmainfo; > > > > > > }; > > > > > > > > > > > > /* Internal representation of a receive virtqueue */ > > > > > > @@ -368,6 +389,95 @@ static struct xdp_frame *ptr_to_xdp(void *ptr) > > > > > > return (struct xdp_frame *)((unsigned long)ptr & ~VIRTIO_XDP_FLAG); > > > > > > } > > > > > > > > > > > > +static struct virtnet_sq_dma *virtnet_sq_unmap(struct send_queue *sq, void **data) > > > > > > +{ > > > > > > + struct virtnet_sq_dma *d; > > > > > > + int i; > > > > > > + > > > > > > + d = *data; > > > > > > + *data = d->data; > > > > > > + > > > > > > + for (i = 0; i < d->num; ++i) > > > > > > + virtqueue_dma_unmap_page_attrs(sq->vq, d->addr[i], d->len[i], > > > > > > + DMA_TO_DEVICE, 0); > > > > > > + > > > > > > + d->next = sq->dmainfo.free; > > > > > > + sq->dmainfo.free = d; > > > > > > + > > > > > > + return d; > > > > > > +} > > > > > > + > > > > > > +static struct virtnet_sq_dma *virtnet_sq_map_sg(struct send_queue *sq, > > > > > > + int nents, void *data) > > > > > > +{ > > > > > > + struct virtnet_sq_dma *d; > > > > > > + struct scatterlist *sg; > > > > > > + int i; > > > > > > + > > > > > > + if (!sq->dmainfo.free) > > > > > > + return NULL; > > > > > > + > > > > > > + d = sq->dmainfo.free; > > > > > > + sq->dmainfo.free = d->next; > > > > > > + > > > > > > + for_each_sg(sq->sg, sg, nents, i) { > > > > > > + if (virtqueue_dma_map_sg_attrs(sq->vq, sg, DMA_TO_DEVICE, 0)) > > > > > > + goto err; > > > > > > + > > > > > > + d->addr[i] = sg->dma_address; > > > > > > + d->len[i] = sg->length; > > > > > > + } > > > > > > + > > > > > > + d->data = data; > > > > > > + d->num = i; > > > > > > + return d; > > > > > > + > > > > > > +err: > > > > > > + d->num = i; > > > > > > + virtnet_sq_unmap(sq, (void **)&d); > > > > > > + return NULL; > > > > > > +} > > > > > > > > > > > > > > > Do I see a reimplementation of linux/llist.h here? > > > > > > > > > > > > > > > > + > > > > > > +static int virtnet_add_outbuf(struct send_queue *sq, u32 num, void *data) > > > > > > +{ > > > > > > + int ret; > > > > > > + > > > > > > + if (sq->vq->premapped) { > > > > > > + data = virtnet_sq_map_sg(sq, num, data); > > > > > > + if (!data) > > > > > > + return -ENOMEM; > > > > > > + } > > > > > > + > > > > > > + ret = virtqueue_add_outbuf(sq->vq, sq->sg, num, data, GFP_ATOMIC); > > > > > > + if (ret && sq->vq->premapped) > > > > > > + virtnet_sq_unmap(sq, &data); > > > > > > + > > > > > > + return ret; > > > > > > +} > > > > > > + > > > > > > +static int virtnet_sq_init_dma_mate(struct send_queue *sq) > > > > > > > > > > Mate? The popular south african drink? > > > > > > > > > > > +{ > > > > > > + struct virtnet_sq_dma *d; > > > > > > + int num, i; > > > > > > + > > > > > > + num = virtqueue_get_vring_size(sq->vq); > > > > > > + > > > > > > + sq->dmainfo.free = kcalloc(num, sizeof(*sq->dmainfo.free), GFP_KERNEL); > > > > > > + if (!sq->dmainfo.free) > > > > > > + return -ENOMEM; > > > > > > > > > > > > > > > This could be quite a bit of memory for a large queue. And for a bunch > > > > > of common cases where unmap is a nop (e.g. iommu pt) this does nothing > > > > > useful at all. And also, this does nothing useful if PLATFORM_ACCESS is off > > > > > which is super common. > > > > > > > > > > A while ago I proposed: > > > > > - extend DMA APIs so one can query whether unmap is a nop > > > > > > > > > > > > We may have trouble for this. > > > > > > > > dma_addr_t dma_map_page_attrs(struct device *dev, struct page *page, > > > > size_t offset, size_t size, enum dma_data_direction dir, > > > > unsigned long attrs) > > > > { > > > > const struct dma_map_ops *ops = get_dma_ops(dev); > > > > dma_addr_t addr; > > > > > > > > BUG_ON(!valid_dma_direction(dir)); > > > > > > > > if (WARN_ON_ONCE(!dev->dma_mask)) > > > > return DMA_MAPPING_ERROR; > > > > > > > > if (dma_map_direct(dev, ops) || > > > > arch_dma_map_page_direct(dev, page_to_phys(page) + offset + size)) > > > > addr = dma_direct_map_page(dev, page, offset, size, dir, attrs); > > > > else > > > > addr = ops->map_page(dev, page, offset, size, dir, attrs); > > > > kmsan_handle_dma(page, offset, size, dir); > > > > debug_dma_map_page(dev, page, offset, size, dir, addr, attrs); > > > > > > > > return addr; > > > > } > > > > > > > > arch_dma_map_page_direct will check the dma address. > > > > So we can not judge by the API in advance. > > > > > > > > Thanks. > > > > > > So if dma_map_direct is false we'll still waste some memory. > > > So be it. > > > > arch_dma_map_page_direct default is marco (false), just for powerpc > > it is a function. So I think we can skip it. > > > > If the dma_map_direct is false, I think should save the dma info. > > > > Thanks. > > > Would already be an improvement. > But can we have better names? > > I'd prefer: > > dma_can_skip_unmap > dma_can_skip_sync > > Because we do not know for sure if it's direct unless > we have the page. we might need to add these callbacks to dma ops too, I think with iommu pt that is the case and it is pretty common, right? > -- > MST