Linux Virtualization - Sep 2018 - [PATCH] vhost: fix VHOST_GET_BACKEND_FEATURES ioctl request definition

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 at altlinux.org>
---
 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

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 at altlinux.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

On 2018?09?04? 10:22, Michael S. Tsirkin wrote:
> 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 at
altlinux.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?
My bad, not intentional. And I agree that fixing this is not too late.

So

Acked-by: Jason Wang <jasowang at redhat.com>
>
>> ---
>>   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