Re: [Xen-devel] [PATCH] xenforeignmemory: work around bug in older privcmd

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Fri, Aug 24, 2018 at 01:16:26PM +0100, Paul Durrant wrote:
> Versions of linux privcmd prior to commit dc9eab6fd94d ("return -ENOTTY
> for unimplemented IOCTLs") will return -EINVAL rather than the conventional
> -ENOTTY for unimplemented codes. This breaks the error path in
> libxenforeignmemory resource mapping, which only translates ENOTTY into
> EOPNOTSUPP to inform callers of the need to use an alternative (legacy)
> mechanism.
> 
> This patch adds a new 'unimplemented' [1] ioctl code into the local
> privcmd header which is then used to probe for the appropriate errno to
> translate in the resource mapping error path
> 
> [1] this is a code that has, so far, never been used in any version of
>     privcmd and will be added to future versions of the header in the
>     linux source, to make sure it stays unimplemented.
> 
> Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
> ---

Acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>

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