linux-kernel - Re: [PATCH 6/8] i915,uaccess: Fix redundant CLAC

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Date:   Thu, 28 Feb 2019 15:10:44 +0000
From:   Chris Wilson <chris@...is-wilson.co.uk>
To:     Peter Zijlstra <peterz@...radead.org>, bp@...en8.de,
        brgerst@...il.com, catalin.marinas@....com, dvlasenk@...hat.com,
        hpa@...or.com, james.morse@....com, jpoimboe@...hat.com,
        julien.thierry@....com, luto@...capital.net, luto@...nel.org,
        mingo@...nel.org, tglx@...utronix.de,
        torvalds@...ux-foundation.org, valentin.schneider@....com,
        will.deacon@....com
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org
Subject: Re: [PATCH 6/8] i915,uaccess: Fix redundant CLAC

Quoting Peter Zijlstra (2019-02-28 14:54:56)
> drivers/gpu/drm/i915/i915_gem_execbuffer.o: warning: objtool: .altinstr_replacement+0x3c: redundant UACCESS disable
> drivers/gpu/drm/i915/i915_gem_execbuffer.o: warning: objtool: .altinstr_replacement+0x66: redundant UACCESS disable
> 
> AKA. you don't need user_access_end() if user_access_begin() fails.

Cool, I had no idea if it was required or not. The closest to
instructions on how to use user_access_begin() is in
arch/x86/include/asm/uaccess.h ... which I guess is earlier in this
series!

> Cc: Chris Wilson <chris@...is-wilson.co.uk>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>

Reviewed-by: Chris Wilson <chris@...is-wilson.co.uk>
-Chris