From mboxrd@z Thu Jan  1 00:00:00 1970
From: shuah <shuah@kernel.org>
Subject: Re: [PATCH for 5.2 07/12] rseq/selftests: s390: use trap4 for
 RSEQ_SIG
Date: Thu, 16 May 2019 14:39:28 -0600
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References: <20190429152803.7719-1-mathieu.desnoyers@efficios.com>
 <20190429152803.7719-8-mathieu.desnoyers@efficios.com>
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To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>, Peter Zijlstra <peterz@infradead.org>, "Paul E . McKenney" <paulmck@linux.vnet.ibm.com>, Boqun Feng <boqun.feng@gmail.com>, Andy Lutomirski <luto@amacapital.net>, Dave Watson <davejwatson@fb.com>, Paul Turner <pjt@google.com>, Andrew Morton <akpm@linux-foundation.org>, Russell King <linux@arm.linux.org.uk>, Ingo Molnar <mingo@redhat.com>, "H . Peter Anvin" <hpa@zytor.com>, Andi Kleen <andi@firstfloor.org>, Chris Lameter <cl@linux.com>, Ben Maurer <bmaurer@fb.com>, Steven Rostedt <rostedt@goodmis.org>, Josh Triplett <josh@joshtriplett.org>, Linus Torvalds <torvalds@linux-foundation.org>, Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will.deacon@arm>
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Hi Mathieu,

On 4/29/19 9:27 AM, Mathieu Desnoyers wrote:
> From: Martin Schwidefsky <schwidefsky@de.ibm.com>
> 
> Use trap4 as the guard instruction for the restartable sequence abort
> handler.
> 
> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
> ---
>   tools/testing/selftests/rseq/rseq-s390.h | 9 ++++++++-
>   1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/rseq/rseq-s390.h b/tools/testing/selftests/rseq/rseq-s390.h
> index 7c4f3a70b6c7..1d05c5187ae6 100644
> --- a/tools/testing/selftests/rseq/rseq-s390.h
> +++ b/tools/testing/selftests/rseq/rseq-s390.h
> @@ -1,6 +1,13 @@
>   /* SPDX-License-Identifier: LGPL-2.1 OR MIT */
>   
> -#define RSEQ_SIG	0x53053053
> +/*
> + * RSEQ_SIG uses the trap4 instruction. As Linux does not make use of the
> + * access-register mode nor the linkage stack this instruction will always
> + * cause a special-operation exception (the trap-enabled bit in the DUCT
> + * is and will stay 0). The instruction pattern is
> + *	b2 ff 0f ff	trap4   4095(%r0)
> + */
> +#define RSEQ_SIG	0xB2FF0FFF
>   
>   #define rseq_smp_mb()	__asm__ __volatile__ ("bcr 15,0" ::: "memory")
>   #define rseq_smp_rmb()	rseq_smp_mb()
> 

I generated my pull request for Linus and did a sanity check and ran
into merge conflict on this patch. Looks like this is already in
Linus's tree.

Can you confirm!

I have to drop this patch and regenerate my pull request. Can you
confirm!

thanks,
-- Shuah