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Sat, 31 Jul 2021 06:47:36 +0000 (GMT) Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 8BD2EAE04D; Sat, 31 Jul 2021 06:47:36 +0000 (GMT) Received: from osiris (unknown [9.145.16.160]) by d06av26.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Sat, 31 Jul 2021 06:47:36 +0000 (GMT) Date: Sat, 31 Jul 2021 08:47:35 +0200 From: Heiko Carstens To: Steven Rostedt Cc: Ilya Leoshkevich , Ingo Molnar , linux-kernel@vger.kernel.org, Sven Schnelle , Vasily Gorbik , linux-s390@vger.kernel.org Subject: Re: [PATCH 1/2] ftrace: Introduce ftrace_need_init_nop() Message-ID: References: <20210728212546.128248-1-iii@linux.ibm.com> <20210728212546.128248-2-iii@linux.ibm.com> <20210730220741.4da6fdf6@oasis.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210730220741.4da6fdf6@oasis.local.home> X-TM-AS-GCONF: 00 X-Proofpoint-GUID: tqCo0P08jxZEBeCc-2YgUKreUEvyOFRR X-Proofpoint-ORIG-GUID: J1IvfW7LxhilDrbsEMhhaQfH8dmY_bzV X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.790 definitions=2021-07-30_11:2021-07-30,2021-07-30 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 adultscore=0 phishscore=0 clxscore=1011 mlxscore=0 impostorscore=0 bulkscore=0 suspectscore=0 malwarescore=0 spamscore=0 mlxlogscore=989 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2107140000 definitions=main-2107310029 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 30, 2021 at 10:07:41PM -0400, Steven Rostedt wrote: > On Wed, 28 Jul 2021 23:25:45 +0200 > Ilya Leoshkevich wrote: > > > Implementing live patching on s390 requires each function's prologue to > > contain a very special kind of nop, which gcc and clang don't generate. > > However, the current code assumes that if CC_USING_NOP_MCOUNT is > > defined, then whatever the compiler generates is good enough. > > > > Move the CC_USING_NOP_MCOUNT check into the new ftrace_need_init_nop() > > macro, that the architectures can override. > > > > An alternative solution is to disable using -mnop-mcount in the > > Makefile, however, this makes the build logic (even) more complicated > > and forces the arch-specific code to deal with the useless __fentry__ > > symbol. > > > > Signed-off-by: Ilya Leoshkevich > > I'm fine with this patch, and also you taking it in via the s390 tree. > > Reviewed-by: Steven Rostedt (VMware) Thanks a lot!