Re: [RFC 1/3] vdpa: support exposing the config size to userspace

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在 2022/1/17 下午5:29, Longpeng(Mike) 写道:
From: Longpeng <longpeng2@xxxxxxxxxx>

- GET_CONFIG_SIZE: the size of the virtio config space


I think we need to be verbose here. And it would be better to quote what spec said:

"

The device MUST allow reading of any device-specific configuration field before FEATURES_OK is set by the driver. This includes fields which are conditional on feature bits, as long as those feature bits are offered by the device.

"

I guess the size should contain the conditional on features bits.

(Or maybe we need to tweak the comment for get_config_size as well).

Other looks good.

Thanks



Signed-off-by: Longpeng <longpeng2@xxxxxxxxxx>
---
  drivers/vhost/vdpa.c       | 17 +++++++++++++++++
  include/uapi/linux/vhost.h |  4 ++++
  2 files changed, 21 insertions(+)

diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
index 29cced1cd277..1eea14a4ea56 100644
--- a/drivers/vhost/vdpa.c
+++ b/drivers/vhost/vdpa.c
@@ -355,6 +355,20 @@ static long vhost_vdpa_get_iova_range(struct vhost_vdpa *v, u32 __user *argp)
  	return 0;
  }
+static long vhost_vdpa_get_config_size(struct vhost_vdpa *v, u32 __user *argp)
+{
+	struct vdpa_device *vdpa = v->vdpa;
+	const struct vdpa_config_ops *ops = vdpa->config;
+	u32 size;
+
+	size = ops->get_config_size(vdpa);
+
+	if (copy_to_user(argp, &size, sizeof(size)))
+		return -EFAULT;
+
+	return 0;
+}
+
  static long vhost_vdpa_vring_ioctl(struct vhost_vdpa *v, unsigned int cmd,
  				   void __user *argp)
  {
@@ -492,6 +506,9 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
  	case VHOST_VDPA_GET_IOVA_RANGE:
  		r = vhost_vdpa_get_iova_range(v, argp);
  		break;
+	case VHOST_VDPA_GET_CONFIG_SIZE:
+		r = vhost_vdpa_get_config_size(v, argp);
+		break;
  	default:
  		r = vhost_dev_ioctl(&v->vdev, cmd, argp);
  		if (r == -ENOIOCTLCMD)
diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h
index c998860d7bbc..bc74e95a273a 100644
--- a/include/uapi/linux/vhost.h
+++ b/include/uapi/linux/vhost.h
@@ -150,4 +150,8 @@
  /* Get the valid iova range */
  #define VHOST_VDPA_GET_IOVA_RANGE	_IOR(VHOST_VIRTIO, 0x78, \
  					     struct vhost_vdpa_iova_range)
+
+/* Get the config size */
+#define VHOST_VDPA_GET_CONFIG_SIZE	_IOR(VHOST_VIRTIO, 0x79, __u32)
+
  #endif

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