This requires that barebox can actually tell apart DMA coherent devices from non-coherent ones, so select OF_DMA_COHERENCY where applicable.
Signed-off-by: Ahmad Fatoum <[email protected]> --- drivers/virtio/Kconfig | 1 + drivers/virtio/virtio.c | 4 +++ drivers/virtio/virtio_ring.c | 62 +++++++----------------------------- 3 files changed, 16 insertions(+), 51 deletions(-) diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig index ecf66987b3ed..e39ec863f003 100644 --- a/drivers/virtio/Kconfig +++ b/drivers/virtio/Kconfig @@ -1,6 +1,7 @@ # SPDX-License-Identifier: GPL-2.0-only config VIRTIO bool + select OF_DMA_COHERENCY if OF help This option is selected by any driver which implements the virtio bus, such as CONFIG_VIRTIO_MMIO, CONFIG_VIRTIO_PCI. diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c index 4abf551a2834..262c09c9fe58 100644 --- a/drivers/virtio/virtio.c +++ b/drivers/virtio/virtio.c @@ -138,6 +138,10 @@ int virtio_finalize_features(struct virtio_device *dev) return -ENODEV; } + /* When this changes in future with support for IOMMUs in + * emulation, make sure to adapt vring_alloc_queue(), so + * it ignores IOMMUs if virtio_has_dma_quirk() + */ if (!virtio_has_feature(dev, VIRTIO_F_ACCESS_PLATFORM)) { dev_warn(&dev->dev, "device must provide VIRTIO_F_ACCESS_PLATFORM\n"); diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index 8b6469f54d2a..8953d43c440c 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -23,9 +23,14 @@ #define vq_info(vq, fmt, ...) \ dev_info(&vq->vdev->dev, fmt, ##__VA_ARGS__) +static inline struct device *virtio_dma_dev(const struct virtio_device *vdev) +{ + return vdev->dev.parent; +} + static inline struct device *vring_dma_dev(const struct virtqueue *vq) { - return vq->vdev->dev.parent; + return virtio_dma_dev(vq->vdev); } /* Map one sg entry. */ @@ -330,11 +335,6 @@ static struct virtqueue *__vring_new_virtqueue(unsigned int index, * On most systems with virtio, physical addresses match bus addresses, * and it _shouldn't_ particularly matter whether we use the DMA API. * - * However, barebox' dma_alloc_coherent doesn't yet take a device pointer - * as argument, so even for dma-coherent devices, the virtqueue is mapped - * uncached on ARM. This has considerable impact on the Virt I/O performance, - * so we really want to avoid using the DMA API if possible for the time being. - * * On some systems, including Xen and any system with a physical device * that speaks virtio behind a physical IOMMU, we must use the DMA API * for virtio DMA to work at all. @@ -344,60 +344,20 @@ static struct virtqueue *__vring_new_virtqueue(unsigned int index, * ignores the IOMMU, so we must either pretend that the IOMMU isn't * there or somehow map everything as the identity. * - * For the time being, we preserve historic behavior and bypass the DMA - * API. - * - * TODO: install a per-device DMA ops structure that does the right thing - * taking into account all the above quirks, and use the DMA API - * unconditionally on data path. + * As we do not support IOMMUs yet amd dma_alloc_cohrent takes a device + * pointer that enables us to do cached DMA, just use the DMA API + * unconditionally for now. */ - -static bool vring_use_dma_api(const struct virtio_device *vdev) -{ - return !virtio_has_dma_quirk(vdev); -} - static void *vring_alloc_queue(struct virtio_device *vdev, size_t size, dma_addr_t *dma_handle) { - if (vring_use_dma_api(vdev)) { - return dma_alloc_coherent(DMA_DEVICE_BROKEN, size, dma_handle); - } else { - void *queue = memalign(PAGE_SIZE, PAGE_ALIGN(size)); - - if (queue) { - phys_addr_t phys_addr = virt_to_phys(queue); - *dma_handle = (dma_addr_t)phys_addr; - - memset(queue, 0x00, PAGE_ALIGN(size)); - - /* - * Sanity check: make sure we dind't truncate - * the address. The only arches I can find that - * have 64-bit phys_addr_t but 32-bit dma_addr_t - * are certain non-highmem MIPS and x86 - * configurations, but these configurations - * should never allocate physical pages above 32 - * bits, so this is fine. Just in case, throw a - * warning and abort if we end up with an - * unrepresentable address. - */ - if (WARN_ON_ONCE(*dma_handle != phys_addr)) { - free(queue); - return NULL; - } - } - return queue; - } + return dma_alloc_coherent(virtio_dma_dev(vdev), size, dma_handle); } static void vring_free_queue(struct virtio_device *vdev, size_t size, void *queue, dma_addr_t dma_handle) { - if (vring_use_dma_api(vdev)) - dma_free_coherent(DMA_DEVICE_BROKEN, queue, dma_handle, size); - else - free(queue); + dma_free_coherent(virtio_dma_dev(vdev), queue, dma_handle, size); } struct virtqueue *vring_create_virtqueue(unsigned int index, unsigned int num, -- 2.47.3
