Re: [PATCH 05/20] x86/uaccess/xen: Suppress SMAP warnings

[Peter Zijlstra]

On Thu, Mar 07, 2019 at 01:22:52PM +0100, Juergen Gross wrote:
> On 07/03/2019 12:45, Peter Zijlstra wrote:
> > drivers/xen/privcmd.o: warning: objtool: privcmd_ioctl()+0x1414: call to hypercall_page() with UACCESS enabled
> > 
> > Xen needs to do HV calls with AC=1 for hysterical raisins. Make the
> > warning go away.
> 
> No, this is a hypercall with parameters passed through from user land
> (Xen tools). So setting AC=1 is not related to hysterical reasons, but
> to indicate that unprivileged buffers are okay here. So please change
> the commit message to something like:
> 
> Some Xen hypercalls allow parameter buffers in user land, so they need
> to set AC=1. Avoid the warning for those cases.

*yuck* that's gross...

And I understood from Andrew yesterday (but perhaps I misunderstood)
that the whole privcmd thing was a bit of a hack.

But sure, I'll change the message.

> > XXX: arguably we should rename ANNOTATE_NOSPEC_ALTERNATIVE to
> >      ANNOTATE_IGNORE_ALTERNATIVE.
> > 
> > Cc: andrew.cooper3@xxxxxxxxxx
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> 
> Mind Cc-ing the maintainers of the code you are touching in future
> patches?

Sure; my bad, I forgot to ask get_maintainers about this.