In order to mmap a dmabuf, we first need to create a placeholder mapping that would fit the entire size of the dmabuf. This mapping would then be replaced with smaller mappings of individual dmabuf segments.
Cc: Alex Williamson <[email protected]> Cc: Cédric Le Goater <[email protected]> Signed-off-by: Vivek Kasireddy <[email protected]> --- hw/vfio/device.c | 65 +++++++++++++++++++++++++++++++++++ include/hw/vfio/vfio-device.h | 16 +++++++++ 2 files changed, 81 insertions(+) diff --git a/hw/vfio/device.c b/hw/vfio/device.c index a7603600f3..ef05ec8ade 100644 --- a/hw/vfio/device.c +++ b/hw/vfio/device.c @@ -725,3 +725,68 @@ bool vfio_device_create_dmabuf(struct iovec *iov, unsigned int iov_cnt, } return true; } + +bool vfio_device_mmap_dmabuf(struct iovec *iov, unsigned int iov_cnt, + void **addr, size_t total_size, Error **errp) +{ + struct vfio_region_info *info = NULL; + VFIODevice *vbasedev = NULL; + ram_addr_t offset, len = 0; + RAMBlock *first_rb, *rb; + void *map, *submap; + int i, index; + + if (!vfio_device_lookup(iov, &vbasedev, errp)) { + return false; + } + + /* + * We first reserve a contiguous chunk of address space for the entire + * dmabuf, then replace it with smaller mappings that correspond to the + * individual segments of the dmabuf. + */ + map = mmap(NULL, total_size, PROT_NONE, MAP_SHARED | MAP_ANONYMOUS, -1, 0); + if (map == MAP_FAILED) { + error_setg_errno(errp, errno, "Could not reserve placeholder mapping"); + return false; + } + + for (i = 0; i < iov_cnt; i++) { + rb = qemu_ram_block_from_host(iov[i].iov_base, false, &offset); + if (i == 0) { + first_rb = rb; + } + if (!rb || rb != first_rb) { + error_setg(errp, "Cannot mmap dmabuf with different regions\n"); + goto err; + } + + index = vfio_get_region_index_from_mr(rb->mr); + if (index < 0) { + error_setg(errp, "Cannot find region index for dmabuf segment\n"); + goto err; + } + + if (!vfio_device_get_region_info(vbasedev, index, &info)) { + error_setg(errp, "Cannot find region info for dmabuf segment\n"); + goto err; + } + + submap = mmap(map + len, iov[i].iov_len, PROT_READ, + MAP_SHARED | MAP_FIXED, vbasedev->fd, + info->offset + offset); + if (submap == MAP_FAILED) { + error_setg(errp, "Could not mmap dmabuf segment\n"); + goto err; + } + + len += iov[i].iov_len; + } + *addr = map; + return true; +err: + munmap(map, total_size); + error_prepend(errp, "VFIO dmabuf mmap failed: "); + return false; +} + diff --git a/include/hw/vfio/vfio-device.h b/include/hw/vfio/vfio-device.h index 003bac10b5..b8e0801b94 100644 --- a/include/hw/vfio/vfio-device.h +++ b/include/hw/vfio/vfio-device.h @@ -332,6 +332,22 @@ int vfio_get_region_index_from_mr(MemoryRegion *mr); */ bool vfio_device_create_dmabuf(struct iovec *iov, unsigned int iov_cnt, int *fd, Error **errp); + +/** + * Mmap a dmabuf by first translating the addresses in the iovec + * array into VFIO region offsets and then creating a placeholder + * mapping that would be replaced later with mappings that + * correspond to the dmabuf segments. + * + * @iov: array of iovec entries associated with the dmabuf + * @iov_cnt: number of entries in the iovec array + * @addr: pointer to store the resulting mmap address + * @total_size: total size of the dmabuf + * + * Returns true on success and false in case of an error. + */ +bool vfio_device_mmap_dmabuf(struct iovec *iov, unsigned int iov_cnt, + void **addr, size_t total_size, Error **errp); #endif /* Returns 0 on success, or a negative errno. */ -- 2.50.1
