On 2020/12/23 下午8:14, Yongji Xie wrote:
On Wed, Dec 23, 2020 at 5:05 PM Jason Wang <jasowang@xxxxxxxxxx> wrote:
On 2020/12/22 下午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@xxxxxxxxxxxxx>
---
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
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