On 2019/9/26 下午9:14, Tiwei Bie wrote:

On Thu, Sep 26, 2019 at 04:35:18AM -0400, Michael S. Tsirkin wrote:

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On Thu, Sep 26, 2019 at 12:54:27PM +0800, Tiwei Bie wrote:

[...]

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diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h
index 40d028eed645..5afbc2f08fa3 100644
--- a/include/uapi/linux/vhost.h
+++ b/include/uapi/linux/vhost.h

@@ -116,4 +116,12 @@
  #define VHOST_VSOCK_SET_GUEST_CID	_IOW(VHOST_VIRTIO, 0x60, __u64)
  #define VHOST_VSOCK_SET_RUNNING		_IOW(VHOST_VIRTIO, 0x61, int)
  
+/* VHOST_MDEV specific defines */
+
+#define VHOST_MDEV_SET_STATE	_IOW(VHOST_VIRTIO, 0x70, __u64)
+
+#define VHOST_MDEV_S_STOPPED	0
+#define VHOST_MDEV_S_RUNNING	1
+#define VHOST_MDEV_S_MAX	2
+
  #endif

So assuming we have an underlying device that behaves like virtio:

I think they are really good questions/suggestions. Thanks!

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1. Should we use SET_STATUS maybe?

I like this idea. I will give it a try.

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2. Do we want a reset ioctl?

I think it is helpful. If we use SET_STATUS, maybe we
can use it to support the reset.

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3. Do we want ability to enable rings individually?

I will make it possible at least in the vhost layer.

Note the API support e.g set_vq_ready().

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4. Does device need to limit max ring size?
5. Does device need to limit max number of queues?

I think so. It's helpful to have ioctls to report the max
ring size and max number of queues.

An issue is the max number of queues is done through a device specific 
way, usually device configuration space. This is supported by the 
transport API, but how to expose it to userspace may need more thought.

Thanks

Thanks!