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Date: Sat, 20 Apr 2024 22:25:40 -0700
From: Josh Poimboeuf <jpoimboe@kernel.org>
To: "Paul E. McKenney" <paulmck@kernel.org>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Daniel Sneddon <daniel.sneddon@linux.intel.com>,
	Pawan Gupta <pawan.kumar.gupta@linux.intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Alexandre Chartre <alexandre.chartre@oracle.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Sean Christopherson <seanjc@google.com>,
	Andrew Cooper <andrew.cooper3@citrix.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Nikolay Borisov <nik.borisov@suse.com>,
	KP Singh <kpsingh@kernel.org>, Waiman Long <longman@redhat.com>,
	Borislav Petkov <bp@alien8.de>, Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCH v4 3/5] x86/syscall: Mark exit[_group] syscall handlers
 __noreturn
Message-ID: <20240421052540.w7gtahoko2qerhqq@treble>
References: <cover.1713559768.git.jpoimboe@kernel.org>
 <3b99cb2919c88ab3d353337423b2f0f1b9173f0a.1713559768.git.jpoimboe@kernel.org>
 <0c410ba5-0e42-43b6-80b8-a69c5419a97d@paulmck-laptop>
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In-Reply-To: <0c410ba5-0e42-43b6-80b8-a69c5419a97d@paulmck-laptop>

On Sat, Apr 20, 2024 at 06:58:58AM -0700, Paul E. McKenney wrote:
> On Fri, Apr 19, 2024 at 02:09:49PM -0700, Josh Poimboeuf wrote:
> > The direct-call syscall dispatch functions don't know that the exit()
> > and exit_group() syscall handlers don't return.  As a result the call
> > sites aren't optimized accordingly.
> > 
> > Fix that by marking those exit syscall declarations as __noreturn.
> > 
> > Fixes the following warnings:
> > 
> >   vmlinux.o: warning: objtool: x64_sys_call+0x2804: __x64_sys_exit() is missing a __noreturn annotation
> >   vmlinux.o: warning: objtool: ia32_sys_call+0x29b6: __ia32_sys_exit_group() is missing a __noreturn annotation
> > 
> > Fixes: 7390db8aea0d ("x86/bhi: Add support for clearing branch history at syscall entry")
> > Reported-by: "Paul E. McKenney" <paulmck@kernel.org>
> > Closes: https://lkml.kernel.org/lkml/6dba9b32-db2c-4e6d-9500-7a08852f17a3@paulmck-laptop
> > Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
> 
> Looks good, but it does not apply on top of current -next and I don't
> trust myself to hand-apply it (something about having just got off of
> a flight across the big pond).
> 
> Could you please let me know what else do I need to pull in to be able
> to cleanly apply this one?

This patch has a dependency on an earlier patch in the set:

  https://lkml.kernel.org/lkml/982d05a2f669140f26500bee643011896d661094.1713559768.git.jpoimboe@kernel.org

Though I think it's not a hard dependency and I could reverse the order
of the patches if needed.

-- 
Josh