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Tue, 26 Apr 2022 04:10:44 GMT Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 46F8811C050; Tue, 26 Apr 2022 04:10:32 +0000 (GMT) Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 40ECF11C04A; Tue, 26 Apr 2022 04:10:30 +0000 (GMT) Received: from [9.43.122.72] (unknown [9.43.122.72]) by d06av25.portsmouth.uk.ibm.com (Postfix) with ESMTP; Tue, 26 Apr 2022 04:10:29 +0000 (GMT) Message-ID: <9bf9eccf-d689-463d-0af2-5b3c65da4aef@linux.ibm.com> Date: Tue, 26 Apr 2022 09:40:29 +0530 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.7.0 Subject: Re: [RFC v4 PATCH 2/5] powerpc/crash hp: introduce a new config option CRASH_HOTPLUG Content-Language: en-US To: Eric DeVolder , Michael Ellerman , linuxppc-dev@ozlabs.org References: <20220411084357.157308-1-sourabhjain@linux.ibm.com> <20220411084357.157308-3-sourabhjain@linux.ibm.com> <874k2mfz5t.fsf@mpe.ellerman.id.au> <35ccca7c-07c2-1fc4-70da-2cc581ba818a@oracle.com> From: Sourabh Jain In-Reply-To: <35ccca7c-07c2-1fc4-70da-2cc581ba818a@oracle.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: A6HpZtOCvS_pFgaVgPrW-M1yjjTpo1Uv X-Proofpoint-ORIG-GUID: kk2tVV-VauJY7fZLejFc6v0xk81t4Qfk 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=2022-04-26_01,2022-04-25_03,2022-02-23_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxscore=0 mlxlogscore=999 spamscore=0 suspectscore=0 priorityscore=1501 impostorscore=0 phishscore=0 lowpriorityscore=0 malwarescore=0 clxscore=1015 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2202240000 definitions=main-2204260024 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: ldufour@linux.ibm.com, kexec@lists.infradead.org, hbathini@linux.ibm.com, bhe@redhat.com Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 21/04/22 20:59, Eric DeVolder wrote: > > > On 4/21/22 06:34, Michael Ellerman wrote: >> Sourabh Jain writes: >>> The option CRASH_HOTPLUG enables, in kernel update to kexec segments on >>> hotplug events. >>> >>> All the updates needed on the capture kernel load path in the kernel >>> for >>> both kexec_load and kexec_file_load system will be kept under this >>> config. >>> >>> Signed-off-by: Sourabh Jain >>> Reviewed-by: Eric DeVolder >>> --- >>>   arch/powerpc/Kconfig | 11 +++++++++++ >>>   1 file changed, 11 insertions(+) >>> >>> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig >>> index b779603978e1..777db33f75b5 100644 >>> --- a/arch/powerpc/Kconfig >>> +++ b/arch/powerpc/Kconfig >>> @@ -623,6 +623,17 @@ config FA_DUMP >>>         If unsure, say "y". Only special kernels like petitboot may >>>         need to say "N" here. >>>   +config CRASH_HOTPLUG >>> +    bool "kernel updates of crash kexec segments" >>> +    depends on CRASH_DUMP && (HOTPLUG_CPU) && KEXEC_FILE >>> +    help >>> +      An efficient way to keep the capture kernel up-to-date with CPU >>> +      hotplug events. On CPU hotplug event the kexec segments of >>> capture >>> +      kernel becomes stale and need to be updated with latest CPU >>> data. >>> +      In this method the kernel performs minimal update to only >>> relevant >>> +      kexec segments on CPU hotplug event, instead of triggering full >>> +      capture kernel reload from userspace using udev rule. >> >> Why would a user ever want to turn this off? >> >> Seems to me we should just make it always behave this way, and not have >> a CONFIG option at all. > > Sourabh, > > Borislav Petkov also requested I remove the config option, which will > be the > case in upcoming v8. > > Where I was using CONFIG_CRASH_HOTPLUG, I've replaced it with the > CONFIG_HOTPLUG_CPU || CONFIG_MEMORY_HOTPLUG. Yes good idea. Even Michael suggested there is no need for new CONFIG option. I will also remove CRASH_HOTPLUG config in the next version. Thanks, Sourabh Jain