Jason Wang
2020-Dec-25 07:02 UTC
[RFC v2 09/13] vduse: Add support for processing vhost iotlb message
On 2020/12/25 ??10:37, Yongji Xie wrote:> On Thu, Dec 24, 2020 at 3:37 PM Yongji Xie <xieyongji at bytedance.com> wrote: >> On Thu, Dec 24, 2020 at 10:41 AM Jason Wang <jasowang at redhat.com> wrote: >>> >>> 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? >>> >> If so, the IOTLB UPDATE is actually triggered by ioctl, but >> IOTLB_INVALIDATE is triggered by the message. Is it a little odd? Or >> how about trigger it when userspace call mmap() on the device fd? >> > Oh sorry, looks like mmap() needs to be called in IOTLB UPDATE message > handler. Is it possible for the vdpa device to know which vdpa bus it > is attached to?We'd better not. It's kind of layer violation. Thanks> So that we can generate this message during probing. > Otherwise, we don't know whether the iova domain of MMU-based IOMMU is > needed. > > Thanks, > Yongji >