linux-kernel - Re: [PATCH] vhost: fix VHOST_GET_BACKEND

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Date:   Mon, 3 Sep 2018 22:22:37 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Gleb Fotengauer-Malinovskiy <glebfm@...linux.org>
Cc:     Jason Wang <jasowang@...hat.com>,
        "David S. Miller" <davem@...emloft.net>, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] vhost: fix VHOST_GET_BACKEND_FEATURES ioctl request
 definition

On Mon, Sep 03, 2018 at 08:59:13PM +0300, Gleb Fotengauer-Malinovskiy wrote:
> The _IOC_READ flag fits this ioctl request more because this request
> actually only writes to, but doesn't read from userspace.
> See NOTEs in include/uapi/asm-generic/ioctl.h for more information.
> 
> Fixes: 429711aec282 ("vhost: switch to use new message format")
> Signed-off-by: Gleb Fotengauer-Malinovskiy <glebfm@...linux.org>

Hmm it does make sense, and it's not too late to fix this up.
Jason, what's your take on this? Was _IOW intentional?


> ---
>  include/uapi/linux/vhost.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h
> index b1e22c40c4b6..84c3de89696a 100644
> --- a/include/uapi/linux/vhost.h
> +++ b/include/uapi/linux/vhost.h
> @@ -176,7 +176,7 @@ struct vhost_memory {
>  #define VHOST_BACKEND_F_IOTLB_MSG_V2 0x1
>  
>  #define VHOST_SET_BACKEND_FEATURES _IOW(VHOST_VIRTIO, 0x25, __u64)
> -#define VHOST_GET_BACKEND_FEATURES _IOW(VHOST_VIRTIO, 0x26, __u64)
> +#define VHOST_GET_BACKEND_FEATURES _IOR(VHOST_VIRTIO, 0x26, __u64)
>  
>  /* VHOST_NET specific defines */
>  
> 
> -- 
> glebfm