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

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Mon, Aug 27, 2018 at 03:04:55AM -0600, Jan Beulich wrote:
> >>> On 24.08.18 at 14:16, <paul.durrant@xxxxxxxxxx> 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.
> 
> Shouldn't this addition happen before the Xen tools side change goes
> in?

It doesn't really make any difference from a practical PoV. Applying
this patch right away helps unblocking various Linux branches.

Wei.

> 
> Jan
> 
> 

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