Re: [RFC v2 4/4] vduse: Add new ioctl VDUSE_GET_RECONNECT_INFO

On Mon, Sep 18, 2023 at 4:49 PM Jason Wang jasowang@redhat.com wrote:

On Tue, Sep 12, 2023 at 11:01 AM Cindy Lu lulu@redhat.com wrote:

...

In VDUSE_GET_RECONNECT_INFO, the Userspace App can get the map size and The number of mapping memory pages from the kernel. The userspace App can use this information to map the pages.

Signed-off-by: Cindy Lu lulu@redhat.com

drivers/vdpa/vdpa_user/vduse_dev.c | 15 +++++++++++++++ include/uapi/linux/vduse.h | 15 +++++++++++++++ 2 files changed, 30 insertions(+)

diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c index 680b23dbdde2..c99f99892b5c 100644 --- a/drivers/vdpa/vdpa_user/vduse_dev.c +++ b/drivers/vdpa/vdpa_user/vduse_dev.c @@ -1368,6 +1368,21 @@ static long vduse_dev_ioctl(struct file *file, unsigned int cmd, ret = 0; break; }

•   case VDUSE_GET_RECONNECT_INFO: {
  

•           struct vduse_reconnect_mmap_info info;
  

•           ret = -EFAULT;
  

•           if (copy_from_user(&info, argp, sizeof(info)))
  

•                   break;
  

•           info.size = PAGE_SIZE;
  

•           info.max_index = dev->vq_num + 1;
  

•           if (copy_to_user(argp, &info, sizeof(info)))
  

•                   break;
  

•           ret = 0;
  

•           break;
  

•   }
    default:
            ret = -ENOIOCTLCMD;
            break;
  

diff --git a/include/uapi/linux/vduse.h b/include/uapi/linux/vduse.h index d585425803fd..ce55e34f63d7 100644 --- a/include/uapi/linux/vduse.h +++ b/include/uapi/linux/vduse.h @@ -356,4 +356,19 @@ struct vhost_reconnect_vring { _Bool avail_wrap_counter; };

+/**

• • struct vduse_reconnect_mmap_info
• • @size: mapping memory size, always page_size here
• • @max_index: the number of pages allocated in kernel,just
• • use for check
• */

+struct vduse_reconnect_mmap_info {

•   __u32 size;
  

•   __u32 max_index;
  

+};

One thing I didn't understand is that, aren't the things we used to store connection info belong to uAPI? If not, how can we make sure the connections work across different vendors/implementations. If yes, where?

Thanks

The process for this reconnecttion is A.The first-time connection 1> The userland app checks if the device exists 2> use the ioctl to create the vduse device 3> Mapping the kernel page to userland and save the App-version/features/other information to this page 4> if the Userland app needs to exit, then the Userland app will only unmap the page and then exit

B, the re-connection 1> the userland app finds the device is existing 2> Mapping the kernel page to userland 3> check if the information in shared memory is satisfied to reconnect,if ok then continue to reconnect 4> continue working

For now these information are all from userland,So here the page will be maintained by the userland App in the previous code we only saved the api-version by uAPI . if we need to support reconnection maybe we need to add 2 new uAPI for this, one of the uAPI is to save the reconnect information and another is to get the information

maybe something like

struct vhost_reconnect_data { uint32_t version; uint64_t features; uint8_t status; struct virtio_net_config config; uint32_t nr_vrings; };

#define VDUSE_GET_RECONNECT_INFO _IOR (VDUSE_BASE, 0x1c, struct vhost_reconnect_data)

#define VDUSE_SET_RECONNECT_INFO _IOWR(VDUSE_BASE, 0x1d, struct vhost_reconnect_data)

Thanks Cindy

...

+#define VDUSE_GET_RECONNECT_INFO \

•   _IOWR(VDUSE_BASE, 0x1b, struct vduse_reconnect_mmap_info)
  

#endif /* _UAPI_VDUSE_H_ */

2.34.3