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Date: Thu, 28 Feb 2019 16:24:32 +0100 From: Peter Zijlstra <peterz@...radead.org> To: Chris Wilson <chris@...is-wilson.co.uk> Cc: 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, linux-kernel@...r.kernel.org Subject: Re: [PATCH 6/8] i915,uaccess: Fix redundant CLAC On Thu, Feb 28, 2019 at 03:10:44PM +0000, Chris Wilson wrote: > 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! Ah, I don't think I put the rules in a comment; that would've been useful I suppose ;-) I did teach the rules to objtool though, and that is in the next patch: https://lkml.kernel.org/r/20190228150152.635362492@infradead.org so at least it will yell at you during compile time when you get it wrong. > > 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> Thanks!
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