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Mon, 16 May 2022 11:11:49 +0000 (GMT) Received: from tuxmaker.boeblingen.de.ibm.com (unknown [9.152.85.9]) by d06av26.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Mon, 16 May 2022 11:11:49 +0000 (GMT) Date: Mon, 16 May 2022 13:11:48 +0200 From: Alexander Gordeev To: Heiko Carstens Cc: Nathan Chancellor , Vasily Gorbik , Jonas Paulsson , Ulrich Weigand , Masahiro Yamada , Alexander Egorenkov , Sven Schnelle , Andreas Krebbel , Nathan Chancellor , Nick Desaulniers , linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org Subject: Re: [PATCH 4/8] s390/entry: workaround llvm's IAS limitations Message-ID: References: <20220511120532.2228616-1-hca@linux.ibm.com> <20220511120532.2228616-5-hca@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-TM-AS-GCONF: 00 X-Proofpoint-GUID: Ah_uCgCogIc6033dF8zDRplK3hk-zIq3 X-Proofpoint-ORIG-GUID: 1y6NPgZ1evu3eDCAvQMH8h0HpMJw65OI X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.858,Hydra:6.0.486,FMLib:17.11.64.514 definitions=2022-05-16_07,2022-05-16_02,2022-02-23_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 spamscore=0 impostorscore=0 adultscore=0 mlxlogscore=999 lowpriorityscore=0 bulkscore=0 suspectscore=0 mlxscore=0 malwarescore=0 priorityscore=1501 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2202240000 definitions=main-2205160065 Precedence: bulk List-ID: X-Mailing-List: linux-s390@vger.kernel.org On Mon, May 16, 2022 at 12:19:45PM +0200, Heiko Carstens wrote: > On Mon, May 16, 2022 at 11:07:43AM +0200, Alexander Gordeev wrote: > > Isn't the machine check handler refers to this memory before checking > > unrecoverable storage errors (with CHKSTG macro) as result of this change? > > Yes, indeed. However implementing this without another register will > be quite of a challenge. So what I would prefer in any case: just > assume that this minimal set of memory accesses work. Actually I'd > seriously like to go a bit further, and even move the checks for > storage errors back to C for two reasons: > > - this would make the machine check handler entry code easier again > - it would also allow to enter the machine check handler with DAT on > > After all we rely anyway on the fact that at least the local lowcore + > the page(s) which contain text are still accessible. Assuming that a > couple of page tables also work won't make this much worse, but the > code much easier. > > So I'd suggest: leave this code as is, and at some later point move > "rework" the early machine check handler code. > > What do you think? Sounds very reasonable. Please, find my: Acked-by: Alexander Gordeev Also, how such a follow-up looks to you? lgr %r14,\reg #ifdef CONFIG_AS_IS_LLVM larl %r13,\start slgr %r14,%r13 clgfrl %r14,.Lrange_size\@ #else slgfi %r14,\start clgfi %r14,\end - \start #endif