linux-kernel - Re: [PATCH] drm/i915: Remove redundant user_access_end() from __copy_from

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Date:   Fri, 26 Jul 2019 21:18:32 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Chris Wilson <chris@...is-wilson.co.uk>
cc:     Josh Poimboeuf <jpoimboe@...hat.com>,
        intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Sedat Dilek <sedat.dilek@...il.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH] drm/i915: Remove redundant user_access_end() from
 __copy_from_user() error path

On Fri, 26 Jul 2019, Chris Wilson wrote:
> Quoting Thomas Gleixner (2019-07-25 22:55:45)
> > On Thu, 25 Jul 2019, Josh Poimboeuf wrote:
> > 
> > > Objtool reports:
> > > 
> > >   drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o: warning: objtool: .altinstr_replacement+0x36: redundant UACCESS disable
> > > 
> > > __copy_from_user() already does both STAC and CLAC, so the
> > > user_access_end() in its error path adds an extra unnecessary CLAC.
> > > 
> > > Fixes: 0b2c8f8b6b0c ("i915: fix missing user_access_end() in page fault exception case")
> > > Reported-by: Thomas Gleixner <tglx@...utronix.de>
> > > Reported-by: Sedat Dilek <sedat.dilek@...il.com>
> > > Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> > > Tested-by: Nick Desaulniers <ndesaulniers@...gle.com>
> > > Tested-by: Sedat Dilek <sedat.dilek@...il.com>
> > > Link: https://github.com/ClangBuiltLinux/linux/issues/617
> > > Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
> > 
> > Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
> 
> Which tree do you plan to apply it to? I can put in drm-intel, and with
> the fixes tag it will percolate through to 5.3 and beyond, but if you
> want to apply it directly to squash the build warnings, feel free.

It would be nice to get it into 5.3. I can route it linuxwards if you give
an Acked-by, but I'm happy to hand it to you :)

Thanks,

	tglx