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Message-ID: <595fe7d6-7876-26e4-0b7c-1d63ca6d7a97@redhat.com>
Date: Thu, 24 Dec 2020 10:41:25 +0800
From: Jason Wang <jasowang@...hat.com>
To: Yongji Xie <xieyongji@...edance.com>
Cc: "Michael S. Tsirkin" <mst@...hat.com>,
Stefan Hajnoczi <stefanha@...hat.com>, sgarzare@...hat.com,
Parav Pandit <parav@...dia.com>, akpm@...ux-foundation.org,
Randy Dunlap <rdunlap@...radead.org>,
Matthew Wilcox <willy@...radead.org>, viro@...iv.linux.org.uk,
axboe@...nel.dk, bcrl@...ck.org, corbet@....net,
virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
kvm@...r.kernel.org, linux-aio@...ck.org,
linux-fsdevel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [External] Re: [RFC v2 09/13] vduse: Add support for processing
vhost iotlb message
On 2020/12/23 下午8:14, Yongji Xie wrote:
> On Wed, Dec 23, 2020 at 5:05 PM Jason Wang <jasowang@...hat.com> 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@...edance.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
>
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