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SubjectRe: [RFC PATCH 10/10] vhost/vdpa: return configuration bytes read and written to user space
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On 2021/2/16 5:44 下午, Stefano Garzarella wrote:
> vdpa_get_config() and vdpa_set_config() now return the amount
> of bytes read and written, so let's return them to the user space.
>
> We also modify vhost_vdpa_config_validate() to return 0 (bytes read
> or written) instead of an error, when the buffer length is 0.
>
> Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
> ---
> drivers/vhost/vdpa.c | 26 +++++++++++++++-----------
> 1 file changed, 15 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> index 21eea2be5afa..b754c53171a7 100644
> --- a/drivers/vhost/vdpa.c
> +++ b/drivers/vhost/vdpa.c
> @@ -191,9 +191,6 @@ static ssize_t vhost_vdpa_config_validate(struct vhost_vdpa *v,
> struct vdpa_device *vdpa = v->vdpa;
> u32 size = vdpa->config->get_config_size(vdpa);
>
> - if (c->len == 0)
> - return -EINVAL;
> -
> return min(c->len, size);
> }
>
> @@ -204,6 +201,7 @@ static long vhost_vdpa_get_config(struct vhost_vdpa *v,
> struct vhost_vdpa_config config;
> unsigned long size = offsetof(struct vhost_vdpa_config, buf);
> ssize_t config_size;
> + long ret;
> u8 *buf;
>
> if (copy_from_user(&config, c, size))
> @@ -217,15 +215,18 @@ static long vhost_vdpa_get_config(struct vhost_vdpa *v,
> if (!buf)
> return -ENOMEM;
>
> - vdpa_get_config(vdpa, config.off, buf, config_size);
> -
> - if (copy_to_user(c->buf, buf, config_size)) {
> - kvfree(buf);
> - return -EFAULT;
> + ret = vdpa_get_config(vdpa, config.off, buf, config_size);
> + if (ret < 0) {
> + ret = -EFAULT;
> + goto out;
> }
>
> + if (copy_to_user(c->buf, buf, config_size))
> + ret = -EFAULT;
> +
> +out:
> kvfree(buf);
> - return 0;
> + return ret;
> }
>
> static long vhost_vdpa_set_config(struct vhost_vdpa *v,
> @@ -235,6 +236,7 @@ static long vhost_vdpa_set_config(struct vhost_vdpa *v,
> struct vhost_vdpa_config config;
> unsigned long size = offsetof(struct vhost_vdpa_config, buf);
> ssize_t config_size;
> + long ret;
> u8 *buf;
>
> if (copy_from_user(&config, c, size))
> @@ -248,10 +250,12 @@ static long vhost_vdpa_set_config(struct vhost_vdpa *v,
> if (IS_ERR(buf))
> return PTR_ERR(buf);
>
> - vdpa_set_config(vdpa, config.off, buf, config_size);
> + ret = vdpa_set_config(vdpa, config.off, buf, config_size);
> + if (ret < 0)
> + ret = -EFAULT;
>
> kvfree(buf);
> - return 0;
> + return ret;
> }


So I wonder whether it's worth to return the number of bytes since we
can't propogate the result to driver or driver doesn't care about that.

Thanks


>
> static long vhost_vdpa_get_features(struct vhost_vdpa *v, u64 __user *featurep)

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