Jason Wang
2020-Dec-24 02:41 UTC
[External] Re: [RFC v2 09/13] vduse: Add support for processing vhost iotlb message
On 2020/12/23 ??8:14, Yongji Xie wrote:> On Wed, Dec 23, 2020 at 5:05 PM Jason Wang <jasowang at redhat.com> wrote: >> >> On 2020/12/22 ??10:52, Xie Yongji wrote: >>> To support vhost-vdpa bus driver, we need a way to share the >>> vhost-vdpa backend process's memory with the userspace VDUSE process. >>> >>> This patch tries to make use of the vhost iotlb message to achieve >>> that. We will get the shm file from the iotlb message and pass it >>> to the userspace VDUSE process. >>> >>> Signed-off-by: Xie Yongji <xieyongji at bytedance.com> >>> --- >>> Documentation/driver-api/vduse.rst | 15 +++- >>> drivers/vdpa/vdpa_user/vduse_dev.c | 147 ++++++++++++++++++++++++++++++++++++- >>> include/uapi/linux/vduse.h | 11 +++ >>> 3 files changed, 171 insertions(+), 2 deletions(-) >>> >>> diff --git a/Documentation/driver-api/vduse.rst b/Documentation/driver-api/vduse.rst >>> index 623f7b040ccf..48e4b1ba353f 100644 >>> --- a/Documentation/driver-api/vduse.rst >>> +++ b/Documentation/driver-api/vduse.rst >>> @@ -46,13 +46,26 @@ The following types of messages are provided by the VDUSE framework now: >>> >>> - VDUSE_GET_CONFIG: Read from device specific configuration space >>> >>> +- VDUSE_UPDATE_IOTLB: Update the memory mapping in device IOTLB >>> + >>> +- VDUSE_INVALIDATE_IOTLB: Invalidate the memory mapping in device IOTLB >>> + >>> Please see include/linux/vdpa.h for details. >>> >>> -In the data path, VDUSE framework implements a MMU-based on-chip IOMMU >>> +The data path of userspace vDPA device is implemented in different ways >>> +depending on the vdpa bus to which it is attached. >>> + >>> +In virtio-vdpa case, VDUSE framework implements a MMU-based on-chip IOMMU >>> driver which supports mapping the kernel dma buffer to a userspace iova >>> region dynamically. The userspace iova region can be created by passing >>> the userspace vDPA device fd to mmap(2). >>> >>> +In vhost-vdpa case, the dma buffer is reside in a userspace memory region >>> +which will be shared to the VDUSE userspace processs via the file >>> +descriptor in VDUSE_UPDATE_IOTLB message. And the corresponding address >>> +mapping (IOVA of dma buffer <-> VA of the memory region) is also included >>> +in this message. >>> + >>> Besides, the eventfd mechanism is used to trigger interrupt callbacks and >>> receive virtqueue kicks in userspace. The following ioctls on the userspace >>> vDPA device fd are provided to support that: >>> diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c >>> index b974333ed4e9..d24aaacb6008 100644 >>> --- a/drivers/vdpa/vdpa_user/vduse_dev.c >>> +++ b/drivers/vdpa/vdpa_user/vduse_dev.c >>> @@ -34,6 +34,7 @@ >>> >>> struct vduse_dev_msg { >>> struct vduse_dev_request req; >>> + struct file *iotlb_file; >>> struct vduse_dev_response resp; >>> struct list_head list; >>> wait_queue_head_t waitq; >>> @@ -325,12 +326,80 @@ static int vduse_dev_set_vq_state(struct vduse_dev *dev, >>> return ret; >>> } >>> >>> +static int vduse_dev_update_iotlb(struct vduse_dev *dev, struct file *file, >>> + u64 offset, u64 iova, u64 size, u8 perm) >>> +{ >>> + struct vduse_dev_msg *msg; >>> + int ret; >>> + >>> + if (!size) >>> + return -EINVAL; >>> + >>> + msg = vduse_dev_new_msg(dev, VDUSE_UPDATE_IOTLB); >>> + msg->req.size = sizeof(struct vduse_iotlb); >>> + msg->req.iotlb.offset = offset; >>> + msg->req.iotlb.iova = iova; >>> + msg->req.iotlb.size = size; >>> + msg->req.iotlb.perm = perm; >>> + msg->req.iotlb.fd = -1; >>> + msg->iotlb_file = get_file(file); >>> + >>> + ret = vduse_dev_msg_sync(dev, msg); >> >> My feeling is that we should provide consistent API for the userspace >> device to use. >> >> E.g we'd better carry the IOTLB message for both virtio/vhost drivers. >> >> It looks to me for virtio drivers we can still use UPDAT_IOTLB message >> by using VDUSE file as msg->iotlb_file here. >> > It's OK for me. One problem is when to transfer the UPDATE_IOTLB > message in virtio cases.Instead of generating IOTLB messages for userspace. How about record the mappings (which is a common case for device have on-chip IOMMU e.g mlx5e and vdpa simlator), then we can introduce ioctl for userspace to query? Thanks> >>> + vduse_dev_msg_put(msg); >>> + fput(file); >>> + >>> + return ret; >>> +} >>> + >>> +static int vduse_dev_invalidate_iotlb(struct vduse_dev *dev, >>> + u64 iova, u64 size) >>> +{ >>> + struct vduse_dev_msg *msg; >>> + int ret; >>> + >>> + if (!size) >>> + return -EINVAL; >>> + >>> + msg = vduse_dev_new_msg(dev, VDUSE_INVALIDATE_IOTLB); >>> + msg->req.size = sizeof(struct vduse_iotlb); >>> + msg->req.iotlb.iova = iova; >>> + msg->req.iotlb.size = size; >>> + >>> + ret = vduse_dev_msg_sync(dev, msg); >>> + vduse_dev_msg_put(msg); >>> + >>> + return ret; >>> +} >>> + >>> +static unsigned int perm_to_file_flags(u8 perm) >>> +{ >>> + unsigned int flags = 0; >>> + >>> + switch (perm) { >>> + case VHOST_ACCESS_WO: >>> + flags |= O_WRONLY; >>> + break; >>> + case VHOST_ACCESS_RO: >>> + flags |= O_RDONLY; >>> + break; >>> + case VHOST_ACCESS_RW: >>> + flags |= O_RDWR; >>> + break; >>> + default: >>> + WARN(1, "invalidate vhost IOTLB permission\n"); >>> + break; >>> + } >>> + >>> + return flags; >>> +} >>> + >>> static ssize_t vduse_dev_read_iter(struct kiocb *iocb, struct iov_iter *to) >>> { >>> struct file *file = iocb->ki_filp; >>> struct vduse_dev *dev = file->private_data; >>> struct vduse_dev_msg *msg; >>> - int size = sizeof(struct vduse_dev_request); >>> + unsigned int flags; >>> + int fd, size = sizeof(struct vduse_dev_request); >>> ssize_t ret = 0; >>> >>> if (iov_iter_count(to) < size) >>> @@ -349,6 +418,18 @@ static ssize_t vduse_dev_read_iter(struct kiocb *iocb, struct iov_iter *to) >>> if (ret) >>> return ret; >>> } >>> + >>> + if (msg->req.type == VDUSE_UPDATE_IOTLB && msg->req.iotlb.fd == -1) { >>> + flags = perm_to_file_flags(msg->req.iotlb.perm); >>> + fd = get_unused_fd_flags(flags); >>> + if (fd < 0) { >>> + vduse_dev_enqueue_msg(dev, msg, &dev->send_list); >>> + return fd; >>> + } >>> + fd_install(fd, get_file(msg->iotlb_file)); >>> + msg->req.iotlb.fd = fd; >>> + } >>> + >>> ret = copy_to_iter(&msg->req, size, to); >>> if (ret != size) { >>> vduse_dev_enqueue_msg(dev, msg, &dev->send_list); >>> @@ -565,6 +646,69 @@ static void vduse_vdpa_set_config(struct vdpa_device *vdpa, unsigned int offset, >>> vduse_dev_set_config(dev, offset, buf, len); >>> } >>> >>> +static void vduse_vdpa_invalidate_iotlb(struct vduse_dev *dev, >>> + struct vhost_iotlb_msg *msg) >>> +{ >>> + vduse_dev_invalidate_iotlb(dev, msg->iova, msg->size); >>> +} >>> + >>> +static int vduse_vdpa_update_iotlb(struct vduse_dev *dev, >>> + struct vhost_iotlb_msg *msg) >>> +{ >>> + u64 uaddr = msg->uaddr; >>> + u64 iova = msg->iova; >>> + u64 size = msg->size; >>> + u64 offset; >>> + struct vm_area_struct *vma; >>> + int ret; >>> + >>> + while (uaddr < msg->uaddr + msg->size) { >>> + vma = find_vma(current->mm, uaddr); >>> + ret = -EINVAL; >>> + if (!vma) >>> + goto err; >>> + >>> + size = min(msg->size, vma->vm_end - uaddr); >>> + offset = (vma->vm_pgoff << PAGE_SHIFT) + uaddr - vma->vm_start; >>> + if (vma->vm_file && (vma->vm_flags & VM_SHARED)) { >>> + ret = vduse_dev_update_iotlb(dev, vma->vm_file, offset, >>> + iova, size, msg->perm); >>> + if (ret) >>> + goto err; >> >> My understanding is that vma is something that should not be known by a >> device. So I suggest to move the above processing to vhost-vdpa.c. >> > Will do it. > > Thanks, > Yongji >