In order to implement VFIO_DEVICE_FEATURE_DMA_BUF, we first need to identify the VFIO region and index the buffer (represented by iovec) belongs to and then translate its addresses to offsets within that region.
The qemu_ram_block_from_host() API gives us both the region and the offset info we need to populate the dma ranges in order to invoke this feature. Cc: Alex Williamson <[email protected]> Cc: Cédric Le Goater <[email protected]> Signed-off-by: Vivek Kasireddy <[email protected]> --- hw/vfio/device.c | 40 +++++++++++++++++++++++++++++++++++ include/hw/vfio/vfio-device.h | 14 ++++++++++++ 2 files changed, 54 insertions(+) diff --git a/hw/vfio/device.c b/hw/vfio/device.c index 9ff73f9941..5417142482 100644 --- a/hw/vfio/device.c +++ b/hw/vfio/device.c @@ -21,6 +21,7 @@ #include "qemu/osdep.h" #include <sys/ioctl.h> +#include "system/ramblock.h" #include "hw/vfio/vfio-device.h" #include "hw/vfio/pci.h" #include "hw/hw.h" @@ -615,3 +616,42 @@ VFIODevice *vfio_device_lookup(MemoryRegion *mr) } return NULL; } + +int vfio_device_create_dmabuf_fd(VFIODevice *vbasedev, + struct iovec *iov, unsigned int iov_cnt) +{ + g_autofree struct vfio_device_feature *feature = NULL; + struct vfio_device_feature_dma_buf *dma_buf; + ram_addr_t offset; + RAMBlock *rb; + size_t argsz; + int i, index; + + argsz = sizeof(*feature) + sizeof (*dma_buf) + + sizeof(struct vfio_region_dma_range) * iov_cnt; + feature = g_malloc0(argsz); + dma_buf = (struct vfio_device_feature_dma_buf *)feature->data; + + for (i = 0; i < iov_cnt; i++) { + rb = qemu_ram_block_from_host(iov[i].iov_base, false, &offset); + if (!rb) { + return -1; + } + + index = vfio_get_region_index_from_mr(rb->mr); + if (index < 0) { + return -1; + } + + dma_buf->region_index = index; + dma_buf->dma_ranges[i].offset = offset; + dma_buf->dma_ranges[i].length = iov[i].iov_len; + } + + dma_buf->nr_ranges = iov_cnt; + dma_buf->open_flags = O_RDONLY | O_CLOEXEC; + feature->argsz = argsz; + feature->flags = VFIO_DEVICE_FEATURE_GET | VFIO_DEVICE_FEATURE_DMA_BUF; + + return vbasedev->io_ops->device_feature(vbasedev, feature); +} diff --git a/include/hw/vfio/vfio-device.h b/include/hw/vfio/vfio-device.h index 2f8087f133..7fc2912f15 100644 --- a/include/hw/vfio/vfio-device.h +++ b/include/hw/vfio/vfio-device.h @@ -309,6 +309,20 @@ int vfio_get_region_index_from_mr(MemoryRegion *mr); * Returns the VFIO device if found or NULL. */ VFIODevice *vfio_device_lookup(MemoryRegion *mr); + +/** + * Create and return a dmabuf fd by first translating the addresses in the + * iovec array into VFIO region offsets and then invoking the + * VFIO_DEVICE_FEATURE_DMA_BUF feature. + * + * @vbasedev: #VFIODevice to use + * @iov: array of iovec entries associated with a buffer + * @iov_cnt: number of entries in the iovec array + * + * Returns the newly created dmabuf fd or -1 on error. + */ +int vfio_device_create_dmabuf_fd(VFIODevice *vbasedev, + struct iovec *iov, unsigned int iov_cnt); #endif /* Returns 0 on success, or a negative errno. */ -- 2.50.1
