On Thu, Mar 2, 2023 at 2:09 PM Michael S. Tsirkin <m...@redhat.com> wrote: > > On Thu, Mar 02, 2023 at 11:26:53AM +0800, Jason Wang wrote: > > On Thu, Mar 2, 2023 at 11:24 AM Xuan Zhuo <xuanz...@linux.alibaba.com> > > wrote: > > > > > > On Thu, 2 Mar 2023 11:05:26 +0800, Jason Wang <jasow...@redhat.com> wrote: > > > > On Thu, Mar 2, 2023 at 10:24 AM Xuan Zhuo <xuanz...@linux.alibaba.com> > > > > wrote: > > > > > > > > > > On Tue, 28 Feb 2023 19:15:23 +0800, Xuan Zhuo > > > > > <xuanz...@linux.alibaba.com> wrote: > > > > > > On Tue, 21 Feb 2023 09:51:07 +0800, Jason Wang > > > > > > <jasow...@redhat.com> wrote: > > > > > > > On Mon, Feb 20, 2023 at 3:02 PM Xuan Zhuo > > > > > > > <xuanz...@linux.alibaba.com> wrote: > > > > > > > > > > > > > > > > On Mon, 20 Feb 2023 13:38:24 +0800, Jason Wang > > > > > > > > <jasow...@redhat.com> wrote: > > > > > > > > > On Tue, Feb 14, 2023 at 3:27 PM Xuan Zhuo > > > > > > > > > <xuanz...@linux.alibaba.com> wrote: > > > > > > > > > > > > > > > > > > > > Added virtio_dma_map() to map DMA addresses for virtual > > > > > > > > > > memory in > > > > > > > > > > advance. The purpose is to keep memory mapped across > > > > > > > > > > multiple add/get > > > > > > > > > > buf operations. > > > > > > > > > > > > > > > > > > I wonder if instead of exporting helpers like this, it might > > > > > > > > > be simple > > > > > > > > > to just export dma_dev then the upper layer can use DMA API > > > > > > > > > at will? > > > > > > > > > > > > > > > > > > > > > > > > The reason for not doing this, Virtio is not just using DMA_DEV > > > > > > > > to mapp, but > > > > > > > > also check whether DMA is used. > > > > > > > > > > > > > > We should let the DMA API decide by exporting a correct dma_dev. > > > > > > > E.g > > > > > > > when ACCESS_PLATFORM is not negotiated, advertising a DMA dev > > > > > > > without > > > > > > > dma_ops. > > > > > > > > > > > > > > > > > > Do you mean we provide this API? > > > > > > > > > > > > virtio_get_dma_dev() > > > > > > > > > > > > If it returns NULL, the caller will use the physical memory address > > > > > > directly. If > > > > > > this func return a dma_dev, the caller should use DMA API. > > > > > > > > > > > > > > > cc the XDP_SOCKET's maintainers. > > > > > > > > > > First of all, Jason does not want to encapsulate the API of DMA by > > > > > Virtio. It is > > > > > best to pass DMA Device to XSK, XSK uses DMA API for DMA MAP > > > > > operation directly. > > > > > I agree with this idea. > > > > > > > > > > However, there are several problems under Virtio: > > > > > 1. In some virtualization scenarios, we do not have to perform DMA > > > > > operations, > > > > > just use the physical address directly. > > > > > > > > This is not a problem, we can simply return the virtio device itself > > > > as the DMA device in this case. Since there's no DMA ops attached, DMA > > > > API will use physical address in this case. > > > > > > Is this like this? So why do we have to deal with it in Virtio Ring? Let > > > me > > > learn it. > > > > It has a long debate and I can't recall too many details. (You can > > search the archives). Michael may show more thoughts here. > > > > One concern is the overhead of the DMA API that needs to be benchmarked. > > > > Thanks > > Concern with what?
Always use the DMA API for virtio devices by drop vq->use_dma_api. For the device that doesn't need quirk, advertise the virtio device as its dma device. Thanks > This patch does not change devices, they are using > the existing API. Xuan Zhuo already showed a benchmark result for AF_XDP. > > > > > > > > > > > > > > > > > 2. The latest Virtio Core supports each rx/tx queue with one DMA > > > > > device. > > > > > Generally, the physical network card has only one device. All > > > > > queues use > > > > > it for DMA operation. > > > > > > > > I'm not sure this is a big deal, we just need to use the per virtqueue > > > > dma device to use DMA API. > > > > > > Yes. > > > > > > > > > > > > > > > > > > > > So I consider this problem again, Virtio Core provides only one API. > > > > > > > > > > * virtio_get_dma_dev(queue) > > > > > > > > > > If the return value is NULL, it means that there is no DMA operation. > > > > > If it is > > > > > not NULL, use DMA API for DMA operation. > > > > > > > > > > The modification of XSK is like this. We may pass NULL as dev to > > > > > xp_dma_map(). > > > > > If dev is NULL, then there is no need to perform DMA and Sync > > > > > operations. > > > > > Otherwise, it will perform DMA operations like other devices. > > > > > > > > As discussed above, it might be easier: > > > > > > > > if (!virtio_has_feature(VIRTIO_F_ACCESS_PLATFORM)) > > > > return virtio_device; > > > > else > > > > return vring_dma_dev(); > > > > > > Yes, according to Jason's opinion, then XSK not need to do any > > > modifications. > > > > > > Thanks. > > Yes AF_XDP does not need the per VQ device hack. > We should probably rethink it. > > But as far as implementation goes, poking at VIRTIO_F_ACCESS_PLATFORM > is wrong. Please use virtio_has_dma_quirk. > > > > > > > > > > > > > > > > > And if the dma_dev of rx and tx is different, then we can only disable > > > > > XDP_SOCKET. > > > > > > > > We can start with this. > > > > > > > > Thanks > > > > > > > > > > > > > > Looking forward to everyone's reply. > > > > > > > > > > Thanks. > > > > > > > > > > > > > > > > > Thanks. > > > > > > > > > > > > > > > > > > > > > > > > > > Thanks > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > (Otherwise the DMA helpers need to grow/shrink as the DMA API > > > > > > > > > evolves?) > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Added virtio_dma_unmap() for unmap DMA address. > > > > > > > > > > > > > > > > > > > > Signed-off-by: Xuan Zhuo <xuanz...@linux.alibaba.com> > > > > > > > > > > --- > > > > > > > > > > drivers/virtio/virtio_ring.c | 92 > > > > > > > > > > ++++++++++++++++++++++++++++++++++++ > > > > > > > > > > include/linux/virtio.h | 9 ++++ > > > > > > > > > > 2 files changed, 101 insertions(+) > > > > > > > > > > > > > > > > > > > > diff --git a/drivers/virtio/virtio_ring.c > > > > > > > > > > b/drivers/virtio/virtio_ring.c > > > > > > > > > > index cd9364eb2345..855338609c7f 100644 > > > > > > > > > > --- a/drivers/virtio/virtio_ring.c > > > > > > > > > > +++ b/drivers/virtio/virtio_ring.c > > > > > > > > > > @@ -3172,4 +3172,96 @@ const struct vring > > > > > > > > > > *virtqueue_get_vring(struct virtqueue *vq) > > > > > > > > > > } > > > > > > > > > > EXPORT_SYMBOL_GPL(virtqueue_get_vring); > > > > > > > > > > > > > > > > > > > > +/** > > > > > > > > > > + * virtio_dma_map_page - get the DMA addr of the memory > > > > > > > > > > for virtio device > > > > > > > > > > + * @dev: virtio device > > > > > > > > > > + * @page: the page of the memory to DMA > > > > > > > > > > + * @offset: the offset of the memory inside page > > > > > > > > > > + * @length: memory length > > > > > > > > > > + * @dir: DMA direction > > > > > > > > > > + * > > > > > > > > > > + * This API is only for pre-mapped buffers, for non > > > > > > > > > > premapped buffers virtio > > > > > > > > > > + * core handles DMA API internally. > > > > > > > > > > + * > > > > > > > > > > + * Returns the DMA addr. DMA_MAPPING_ERROR means error. > > > > > > > > > > + */ > > > > > > > > > > +dma_addr_t virtio_dma_map_page(struct device *dev, struct > > > > > > > > > > page *page, size_t offset, > > > > > > > > > > + unsigned int length, enum > > > > > > > > > > dma_data_direction dir) > > > > > > > > > > +{ > > > > > > > > > > > > > > > > > > This (and the reset) needs to be done per virtqueue instead > > > > > > > > > per device > > > > > > > > > after b0e504e5505d184b0be248b7dcdbe50b79f03758 ("virtio_ring: > > > > > > > > > per > > > > > > > > > virtqueue dma device"). > > > > > > > > > > > > > > > > > > > > > > > > YES. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > + struct virtio_device *vdev = dev_to_virtio(dev); > > > > > > > > > > + > > > > > > > > > > + if (!vring_use_dma_api(vdev)) > > > > > > > > > > + return page_to_phys(page) + offset; > > > > > > > > > > + > > > > > > > > > > + return dma_map_page(vdev->dev.parent, page, offset, > > > > > > > > > > length, dir); > > > > > > > > > > +} > > > > > > > > > > > > > > > > > > Need either inline or EXPORT_SYMBOL_GPL() here. > > > > > > > > > > > > > > > > Because I did not use this interface, I did not export it. > > > > > > > > > > > > > > > > Thanks. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Thanks > > > > > > > > > > > > > > > > > > > > > > > > > > > > + > > > > > > > > > > +/** > > > > > > > > > > + * virtio_dma_map - get the DMA addr of the memory for > > > > > > > > > > virtio device > > > > > > > > > > + * @dev: virtio device > > > > > > > > > > + * @addr: the addr to DMA > > > > > > > > > > + * @length: memory length > > > > > > > > > > + * @dir: DMA direction > > > > > > > > > > + * > > > > > > > > > > + * This API is only for pre-mapped buffers, for non > > > > > > > > > > premapped buffers virtio > > > > > > > > > > + * core handles DMA API internally. > > > > > > > > > > + * > > > > > > > > > > + * Returns the DMA addr. > > > > > > > > > > + */ > > > > > > > > > > +dma_addr_t virtio_dma_map(struct device *dev, void *addr, > > > > > > > > > > unsigned int length, > > > > > > > > > > + enum dma_data_direction dir) > > > > > > > > > > +{ > > > > > > > > > > + struct page *page; > > > > > > > > > > + size_t offset; > > > > > > > > > > + > > > > > > > > > > + page = virt_to_page(addr); > > > > > > > > > > + offset = offset_in_page(addr); > > > > > > > > > > + > > > > > > > > > > + return virtio_dma_map_page(dev, page, offset, > > > > > > > > > > length, dir); > > > > > > > > > > +} > > > > > > > > > > +EXPORT_SYMBOL_GPL(virtio_dma_map); > > > > > > > > > > + > > > > > > > > > > +/** > > > > > > > > > > + * virtio_dma_mapping_error - check dma address > > > > > > > > > > + * @dev: virtio device > > > > > > > > > > + * @addr: DMA address > > > > > > > > > > + * > > > > > > > > > > + * This API is only for pre-mapped buffers, for non > > > > > > > > > > premapped buffers virtio > > > > > > > > > > + * core handles DMA API internally. > > > > > > > > > > + * > > > > > > > > > > + * Returns 0 means dma valid. Other means invalid dma > > > > > > > > > > address. > > > > > > > > > > + */ > > > > > > > > > > +int virtio_dma_mapping_error(struct device *dev, > > > > > > > > > > dma_addr_t addr) > > > > > > > > > > +{ > > > > > > > > > > + struct virtio_device *vdev = dev_to_virtio(dev); > > > > > > > > > > + > > > > > > > > > > + if (!vring_use_dma_api(vdev)) > > > > > > > > > > + return 0; > > > > > > > > > > + > > > > > > > > > > + return dma_mapping_error(vdev->dev.parent, addr); > > > > > > > > > > +} > > > > > > > > > > +EXPORT_SYMBOL_GPL(virtio_dma_mapping_error); > > > > > > > > > > + > > > > > > > > > > +/** > > > > > > > > > > + * virtio_dma_unmap - unmap DMA addr > > > > > > > > > > + * @dev: virtio device > > > > > > > > > > + * @dma: DMA address > > > > > > > > > > + * @length: memory length > > > > > > > > > > + * @dir: DMA direction > > > > > > > > > > + * > > > > > > > > > > + * This API is only for pre-mapped buffers, for non > > > > > > > > > > premapped buffers virtio > > > > > > > > > > + * core handles DMA API internally. > > > > > > > > > > + */ > > > > > > > > > > +void virtio_dma_unmap(struct device *dev, dma_addr_t dma, > > > > > > > > > > unsigned int length, > > > > > > > > > > + enum dma_data_direction dir) > > > > > > > > > > +{ > > > > > > > > > > + struct virtio_device *vdev = dev_to_virtio(dev); > > > > > > > > > > + > > > > > > > > > > + if (!vring_use_dma_api(vdev)) > > > > > > > > > > + return; > > > > > > > > > > + > > > > > > > > > > + dma_unmap_page(vdev->dev.parent, dma, length, dir); > > > > > > > > > > +} > > > > > > > > > > +EXPORT_SYMBOL_GPL(virtio_dma_unmap); > > > > > > > > > > + > > > > > > > > > > MODULE_LICENSE("GPL"); > > > > > > > > > > diff --git a/include/linux/virtio.h b/include/linux/virtio.h > > > > > > > > > > index 3ebb346ebb7c..b5fa71476737 100644 > > > > > > > > > > --- a/include/linux/virtio.h > > > > > > > > > > +++ b/include/linux/virtio.h > > > > > > > > > > @@ -9,6 +9,7 @@ > > > > > > > > > > #include <linux/device.h> > > > > > > > > > > #include <linux/mod_devicetable.h> > > > > > > > > > > #include <linux/gfp.h> > > > > > > > > > > +#include <linux/dma-mapping.h> > > > > > > > > > > > > > > > > > > > > /** > > > > > > > > > > * struct virtqueue - a queue to register buffers for > > > > > > > > > > sending or receiving. > > > > > > > > > > @@ -216,4 +217,12 @@ void unregister_virtio_driver(struct > > > > > > > > > > virtio_driver *drv); > > > > > > > > > > #define module_virtio_driver(__virtio_driver) \ > > > > > > > > > > module_driver(__virtio_driver, > > > > > > > > > > register_virtio_driver, \ > > > > > > > > > > unregister_virtio_driver) > > > > > > > > > > + > > > > > > > > > > +dma_addr_t virtio_dma_map_page(struct device *dev, struct > > > > > > > > > > page *page, size_t offset, > > > > > > > > > > + unsigned int length, enum > > > > > > > > > > dma_data_direction dir); > > > > > > > > > > +dma_addr_t virtio_dma_map(struct device *dev, void *addr, > > > > > > > > > > unsigned int length, > > > > > > > > > > + enum dma_data_direction dir); > > > > > > > > > > +int virtio_dma_mapping_error(struct device *dev, > > > > > > > > > > dma_addr_t addr); > > > > > > > > > > +void virtio_dma_unmap(struct device *dev, dma_addr_t dma, > > > > > > > > > > unsigned int length, > > > > > > > > > > + enum dma_data_direction dir); > > > > > > > > > > #endif /* _LINUX_VIRTIO_H */ > > > > > > > > > > -- > > > > > > > > > > 2.32.0.3.g01195cf9f > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > _______________________________________________ > > > > > > Virtualization mailing list > > > > > > Virtualization@lists.linux-foundation.org > > > > > > https://lists.linuxfoundation.org/mailman/listinfo/virtualization > > > > > > > > > > > > > _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization