From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id E6C9FC3DA6E for ; Sun, 17 Dec 2023 15:51:49 +0000 (UTC) Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=ibm.com header.i=@ibm.com header.a=rsa-sha256 header.s=pp1 header.b=NeDYWN4+; dkim-atps=neutral Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4StSBD27Kcz3bqD for ; Mon, 18 Dec 2023 02:51:48 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=ibm.com header.i=@ibm.com header.a=rsa-sha256 header.s=pp1 header.b=NeDYWN4+; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=linux.ibm.com (client-ip=148.163.158.5; helo=mx0b-001b2d01.pphosted.com; envelope-from=sourabhjain@linux.ibm.com; receiver=lists.ozlabs.org) Received: from mx0b-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4StS9F3LjNz2yVG for ; Mon, 18 Dec 2023 02:50:57 +1100 (AEDT) Received: from pps.filterd (m0353722.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.17.1.19/8.17.1.19) with ESMTP id 3BHFbuEs031869 for ; Sun, 17 Dec 2023 15:50:53 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=message-id : date : mime-version : subject : to : references : from : in-reply-to : content-type : content-transfer-encoding; s=pp1; bh=NV4tShkLVg5GALfBCzgOMEzab3+D71ASFGI2naml3dg=; b=NeDYWN4+zgOI3JFdBBieV492Tler+CYJ6BVAOtnayqNGCoPhk9itki6H64UsS95EPo7Y iFH/WP2V1l3s9gDi3t6cq9fhOrYob+nsR/PiHUDWXkcZC8ytt5ej2tnFNRnTsyaxqOY4 nxWvKHX9zJq9Tof6NXpy0Ydiwe9cV11wSNu1ZDy/6ZKSDk2+yeH56CwJUbFrCBY/1f2z uHcP5SBuTm3cwQL5im7M3xnpFhWeIqeRuoj6m30NYSTN9aiQd9YPz321+oHzqrP87psI d17/vi6gjueYyZAQ53D6vr0uMA5tXZ5A7n7V3ovSfAjQujnXW5ueuz58ngo14o/95HfH Ew== Received: from ppma11.dal12v.mail.ibm.com (db.9e.1632.ip4.static.sl-reverse.com [50.22.158.219]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 3v1wdssres-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT) for ; Sun, 17 Dec 2023 15:50:53 +0000 Received: from pps.filterd (ppma11.dal12v.mail.ibm.com [127.0.0.1]) by ppma11.dal12v.mail.ibm.com (8.17.1.19/8.17.1.19) with ESMTP id 3BHEb3ln012313 for ; Sun, 17 Dec 2023 15:50:52 GMT Received: from smtprelay05.fra02v.mail.ibm.com ([9.218.2.225]) by ppma11.dal12v.mail.ibm.com (PPS) with ESMTPS id 3v1rx1axbp-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT) for ; Sun, 17 Dec 2023 15:50:52 +0000 Received: from smtpav06.fra02v.mail.ibm.com (smtpav06.fra02v.mail.ibm.com [10.20.54.105]) by smtprelay05.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 3BHFooUt5636818 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK) for ; Sun, 17 Dec 2023 15:50:51 GMT Received: from smtpav06.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id BBB3120040 for ; Sun, 17 Dec 2023 15:50:50 +0000 (GMT) Received: from smtpav06.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 5BE7D2004B for ; Sun, 17 Dec 2023 15:50:50 +0000 (GMT) Received: from [9.79.190.165] (unknown [9.79.190.165]) by smtpav06.fra02v.mail.ibm.com (Postfix) with ESMTP for ; Sun, 17 Dec 2023 15:50:50 +0000 (GMT) Message-ID: Date: Sun, 17 Dec 2023 21:20:49 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v14 3/6] crash: add a new kexec flag for FDT update To: linuxppc-dev@lists.ozlabs.org References: <20231211083056.340404-1-sourabhjain@linux.ibm.com> <20231211083056.340404-4-sourabhjain@linux.ibm.com> <7fe7b62f-d3fc-4035-96fe-1ab0e3e743c0@linux.ibm.com> <67cadf74-6ae6-4f37-8645-af1833b13196@linux.ibm.com> Content-Language: en-US From: Sourabh Jain In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: J_vmVaydHxtQHDeCJph8wX41oG74u0gO X-Proofpoint-ORIG-GUID: J_vmVaydHxtQHDeCJph8wX41oG74u0gO X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.272,Aquarius:18.0.997,Hydra:6.0.619,FMLib:17.11.176.26 definitions=2023-12-17_03,2023-12-14_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 priorityscore=1501 spamscore=0 phishscore=0 clxscore=1015 impostorscore=0 mlxscore=0 bulkscore=0 adultscore=0 mlxlogscore=999 suspectscore=0 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2311290000 definitions=main-2312170118 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: , Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 17/12/23 06:29, Baoquan He wrote: > On 12/17/23 at 12:27am, Sourabh Jain wrote: >> >> On 16/12/23 15:11, Baoquan He wrote: >>> On 12/15/23 at 12:17pm, Sourabh Jain wrote: >>> ...... >>>>>> diff --git a/include/linux/kexec.h b/include/linux/kexec.h >>>>>> index 0f6ea35879ee..bcedb7625b1f 100644 >>>>>> --- a/include/linux/kexec.h >>>>>> +++ b/include/linux/kexec.h >>>>>> @@ -319,6 +319,7 @@ struct kimage { >>>>>> #ifdef CONFIG_CRASH_HOTPLUG >>>>>> /* If set, allow changes to elfcorehdr of kexec_load'd image */ >>>>>> unsigned int update_elfcorehdr:1; >>>>>> + unsigned int update_fdt:1; >>>>> Can we unify this to one flag, e.g hotplug_update? >>>>> >>>>> With this, on x86_64, we will skip the sha calculation for elfcorehdr. >>>>> On ppc, we will skip the sha calculation for elfcorehdr and fdt. >>>> Yeah, that's what I suggested to Eric. I can do that, but I see one >>>> problem with powerpc or other platforms that need to skip SHA >>>> for more kexec segments in addition to elfcorehdr. >>>> >>>> `update_elfcorehdr` is set when the kexec tool sends the >>>> `KEXEC_UPDATE_ELFCOREHDR` >>>> flag to the kernel for the `kexec_load` system call. >>>> >>>> Given that the kexec tool has already been updated to send the >>>> `KEXEC_UPDATE_ELFCOREHDR` flag only when elfcorehdr is skipped from >>>> SHA verification in generic code, now it would be tricky for architectures >>>> to >>>> determine whether kexec has skipped SHA verification for just elfcorehdr >>>> or all segments needed on the platform with the same flag. >>> In kexec-tools, it's judged by do_hotplug to skip the elfcorehdr >>> segment. I am wondering how you skip the fdt segment when calculating >>> and verifying sha, only saw the update_fdt mark. >> In the kexec tool where we loop through all the kexec segments to calculate >> the SHA, there will be a arch call made to determine whether the segment >> needs >> to be excluded from SHA or not. > OK, a arch call will be added to exclude segments in the ARCH. And the > elfcorehdr segment need be excluded in x86 ARCH in case other ARCH later > may not want to exclude elfcorehdr. Yes, Arch can choose which segment to exclude. > >> Now in the arch function if decide a specific segment needs to excluded then >> corresponding flag is also set by arch function to communicate same with the >> kernel. > But I don't see how you exclude elfcorehdr and fdt in kernel for > kexec_file codes. It's not happening in kexec-tools. On PowerPC, SHA verification is NOT performed for the kexec_file_load case; hence, you won't find any code changes in my patch series to exclude FDT in the kernel code. However, let's consider a scenario where it gets added in the future, or other architectures need to skip the kexec segment, in addition to elfcorehdr. In that case, we can use the same setup as you suggested below. For each kexec segment, there should be an architecture-specific function call to decide whether the segment needs to be excluded or not. > >>> About the existing KEXEC_UPDATE_ELFCOREHDR, we only rename the macro, >>> but still use the same value, could you think of what problem could be >>> caused between kernel and kexec-tools utility, the old and new version >>> compatibility? >> Just changing the macro name will NOT help because the current kexec tool >> enables the KEXEC_UPDATE_ELFCOREHDR = 0x00000004 kexec flag bit >> if >> the command argument --hotplug is passed to the kexec >> and >> the /sys/kernel/crash_elfcorehdr_size file exists in the system. > As we have discussed, excluding will be done in each ARCH's function > when doing sha calculation in kexec-tools, isn't it? > > diff --git a/kexec/kexec.c b/kexec/kexec.c > index b5393e3b20aa..0095aeec988a 100644 > --- a/kexec/kexec.c > +++ b/kexec/kexec.c > @@ -701,10 +701,10 @@ static void update_purgatory(struct kexec_info *info) > continue; > } > > - /* Don't include elfcorehdr in the checksum, if hotplug > + /* Don't include unwanted segments in the checksum, if hotplug > * support enabled. > - */ > - if (do_hotplug && (info->segment[i].mem == (void *)info->elfcorehdr)) { > + if (do_hotplug) > + arch_exclude_segments(info, &i) > continue; > } Yes, something like the above should work. > > >> Now, let's say an architecture enables this feature in the kernel with the >> assumption >> that the 0x00000004 kexec flag bit is passed from the kexec tool when all >> the required >> kexec segments are skipped from SHA calculation. In this case, the current >> kexec tool, >> which passes the 0x00000004 kexec flag bit only when the elfcorehdr is >> skipped, will >> cause issues for architectures. >> >>> If it's about the new header files installed on older kernel, we can >>> change it like below? Fortunately only one release, 6.6 passed. >>> >>> diff --git a/include/uapi/linux/kexec.h b/include/uapi/linux/kexec.h >>> index 3d5b3d757bed..df6a6505e267 100644 >>> --- a/include/uapi/linux/kexec.h >>> +++ b/include/uapi/linux/kexec.h >>> @@ -13,7 +13,7 @@ >>> #define KEXEC_ON_CRASH 0x00000001 >>> #define KEXEC_PRESERVE_CONTEXT 0x00000002 >>> -#define KEXEC_UPDATE_FDT 0x00000008 >>> +#define KEXEC_CRASH_HOTPLUG_UPDATE 0x00000004 >>> #define KEXEC_UPDATE_ELFCOREHDR 0x00000004 >>> #define KEXEC_ARCH_MASK 0xffff0000 >>> /* >>> >>> With my understanding, the kexec flag should be indicating the action, >>> the mem/cpu hotplug, but not relating to any detail. Imagine later >>> another segment need be skipped on one ARCH again, then another flag >>> need be added, this sounds not reasonable. >> I strongly agree with you. The KEXEC_CRASH_HOTPLUG_UPDATE kexec flag >> should be sufficient to inform the kernel that the kexec tool has been >> updated >> to support CPU/Memory hotplug for the kexec_load system call. Unfortunately, >> we cannot use the 0x00000004 kexec flags bit for KEXEC_CRASH_HOTPLUG_UPDATE >> at the moment. > I am fine with 0x00000008 and a new flag, it has the same effect as > #define KEXEC_CRASH_HOTPLUG_UPDATE 0x00000004 > > I am worried about the header file incompatiblity. If we are OK to have KEXEC_CRASH_HOTPLUG_UPDATE 0x00000008 as new bit to introduce CPU/Memory hotplug feature for kexec_load syscall, we will not have compatibility issue. Let me write next version for this patch with KEXEC_CRASH_HOTPLUG_UPDATE 0x00000008 as new flag bit and show how it will be handled. I will also share kexec code for clarity. Thanks, Sourabh > >> What about using 0x00000008 for the KEXEC_CRASH_HOTPLUG_UPDATE flag? >> >> I am aware that we are utilizing two kexec flag bits (0x00000004 and >> 0x00000008) >> for the same feature, but what other options do we have? >> >> Thanks, >> Sourabh >>>> Code snippet from the kexec tool: >>>> >>>> main() { >>>>     ... >>>>     /* NOTE: Xen KEXEC_LIVE_UPDATE and KEXEC_UPDATE_ELFCOREHDR collide */ >>>>     if (do_hotplug) { >>>>         ... >>>> >>>>         /* Indicate to the kernel it is ok to modify the elfcorehdr */ >>>>         kexec_flags |= KEXEC_UPDATE_ELFCOREHDR; >>>>     } >>>>     ... >>>> } >>>> >>>> Any suggestion how to handle this with just one kexec flag? >>>> >>>> Thanks for the review. >>>> >>>> Thanks, >>>> Sourabh Jain >>>> >>>>>> #endif >>>>>> #ifdef ARCH_HAS_KIMAGE_ARCH >>>>>> @@ -396,9 +397,10 @@ bool kexec_load_permitted(int kexec_image_type); >>>>>> /* List of defined/legal kexec flags */ >>>>>> #ifndef CONFIG_KEXEC_JUMP >>>>>> -#define KEXEC_FLAGS (KEXEC_ON_CRASH | KEXEC_UPDATE_ELFCOREHDR) >>>>>> +#define KEXEC_FLAGS (KEXEC_ON_CRASH | KEXEC_UPDATE_ELFCOREHDR | KEXEC_UPDATE_FDT) >>>>>> #else >>>>>> -#define KEXEC_FLAGS (KEXEC_ON_CRASH | KEXEC_PRESERVE_CONTEXT | KEXEC_UPDATE_ELFCOREHDR) >>>>>> +#define KEXEC_FLAGS (KEXEC_ON_CRASH | KEXEC_PRESERVE_CONTEXT | KEXEC_UPDATE_ELFCOREHDR | \ >>>>>> + KEXEC_UPDATE_FDT) >>>>>> #endif >>>>>> /* List of defined/legal kexec file flags */ >>>>>> diff --git a/include/uapi/linux/kexec.h b/include/uapi/linux/kexec.h >>>>>> index 01766dd839b0..3d5b3d757bed 100644 >>>>>> --- a/include/uapi/linux/kexec.h >>>>>> +++ b/include/uapi/linux/kexec.h >>>>>> @@ -13,6 +13,7 @@ >>>>>> #define KEXEC_ON_CRASH 0x00000001 >>>>>> #define KEXEC_PRESERVE_CONTEXT 0x00000002 >>>>>> #define KEXEC_UPDATE_ELFCOREHDR 0x00000004 >>>>>> +#define KEXEC_UPDATE_FDT 0x00000008 >>>>>> #define KEXEC_ARCH_MASK 0xffff0000 >>>>>> /* >>>>>> diff --git a/kernel/kexec.c b/kernel/kexec.c >>>>>> index 8f35a5a42af8..97eb151cd931 100644 >>>>>> --- a/kernel/kexec.c >>>>>> +++ b/kernel/kexec.c >>>>>> @@ -132,6 +132,8 @@ static int do_kexec_load(unsigned long entry, unsigned long nr_segments, >>>>>> #ifdef CONFIG_CRASH_HOTPLUG >>>>>> if (flags & KEXEC_UPDATE_ELFCOREHDR) >>>>>> image->update_elfcorehdr = 1; >>>>>> + if (flags & KEXEC_UPDATE_FDT) >>>>>> + image->update_fdt = 1; >>>>>> #endif >>>>>> ret = machine_kexec_prepare(image); >>>>>> -- >>>>>> 2.41.0 >>>>>>