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

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Message-ID: <689d6dc2-77d6-018e-b156-979b2724be7b@suse.com>
Date:   Thu, 7 Mar 2019 13:22:52 +0100
From:   Juergen Gross <jgross@...e.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        torvalds@...ux-foundation.org, tglx@...utronix.de, hpa@...or.com,
        julien.thierry@....com, will.deacon@....com, luto@...capital.net,
        mingo@...nel.org, catalin.marinas@....com, james.morse@....com,
        valentin.schneider@....com, brgerst@...il.com, jpoimboe@...hat.com,
        luto@...nel.org, bp@...en8.de, dvlasenk@...hat.com
Cc:     linux-kernel@...r.kernel.org, dvyukov@...gle.com,
        rostedt@...dmis.org, andrew.cooper3@...rix.com,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Stefano Stabellini <sstabellini@...nel.org>
Subject: Re: [PATCH 05/20] x86/uaccess/xen: Suppress SMAP warnings

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.

> XXX: arguably we should rename ANNOTATE_NOSPEC_ALTERNATIVE to
>      ANNOTATE_IGNORE_ALTERNATIVE.
> 
> Cc: andrew.cooper3@...rix.com
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>

Mind Cc-ing the maintainers of the code you are touching in future
patches?

With the commit message adjusted:

Reviewed-by: Juergen Gross <jgross@...e.com>


Juergen