Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <d7dd336e-10ef-1674-05fe-45a755bca8d6@oracle.com>
Date:   Fri, 9 Sep 2022 16:28:09 -0500
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101
 Thunderbird/91.3.1
Subject: Re: [PATCH v11 3/7] crash: add generic infrastructure for crash
 hotplug support
Content-Language: en-US
To:     Baoquan He <bhe@redhat.com>
Cc:     linux-kernel@vger.kernel.org, x86@kernel.org,
        kexec@lists.infradead.org, ebiederm@xmission.com,
        dyoung@redhat.com, vgoyal@redhat.com, tglx@linutronix.de,
        mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com,
        hpa@zytor.com, nramas@linux.microsoft.com, thomas.lendacky@amd.com,
        robh@kernel.org, efault@gmx.de, rppt@kernel.org, david@redhat.com,
        sourabhjain@linux.ibm.com, konrad.wilk@oracle.com,
        boris.ostrovsky@oracle.com
References: <20220826173704.1895-1-eric.devolder@oracle.com>
 <20220826173704.1895-4-eric.devolder@oracle.com>
 <Yw7U5jYKcwZ+cMpu@MiWiFi-R3L-srv>
From:   Eric DeVolder <eric.devolder@oracle.com>
In-Reply-To: <Yw7U5jYKcwZ+cMpu@MiWiFi-R3L-srv>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?UjJrSHIrNWh0U1RqSEloZURrR2k2MWVFS2JjN3Z6cWo0Sytvd3FhQ3M1WXVu?=
 =?utf-8?B?a0xCTUh2V2ZNVXZFME9sQmlEbmJ2RDdScGh0ZllZcEFYM2U2VldVNkxtNVlE?=
 =?utf-8?B?MUpxZzdjZ2svTWpDTHdZM3pmNlFlUFhOREIxcWlhSzluT3l5Znl3UUlJanMx?=
 =?utf-8?B?d0RMN211UXR3SXE2cnIzRk9HRHl5VDd2QkYwZHFnVUVCTEFoTVdSL21KZXN3?=
 =?utf-8?B?Q2s3RlBtUDBBbVY3bVFCRy9XcDV2T2xPdlRmd1ZOSDg2a2I3YlZxSE1tNzQ2?=
 =?utf-8?B?K2paTDdJQnBTU1M4RU5RKy9BbmxNMFQ2em9UeUN6NEhKMnBMM3NSSUo3WWQw?=
 =?utf-8?B?WVo5cjVhNEx5aVFMUEFPSXZQT2tCTStIbEJMMkZmSEVwVmh3QmhaRUlpZ3Y4?=
 =?utf-8?B?UW50KzNEb1pSY3dpSG1MOUdqVm9sRG9Xckw3OHl2T0RweXFtZTc1enNJSDJj?=
 =?utf-8?B?SGQ1cUNscU1FQ2pEbVp4Qy81VVdydmMvOCthK0JXZW9SclBYVW00c0JwcFdM?=
 =?utf-8?B?K1BweEM5U2FYa3hWWXc5SnQ5S1JsdFVFRE8zNmpYRVg0VjdiQnhxeXdLZW9k?=
 =?utf-8?B?Zi9CWWozK2dWdjBVSHBMOFMvckcvYlZYVmlURWhhUks1dkJNZm1FOWpZM1lW?=
 =?utf-8?B?amxwUHpZYnNyUWU1ZlpIcVNpd1p6SHJzazVnRkl5R0JlTlhDNW1YOTRmclRn?=
 =?utf-8?B?R000S0xpUXYyUU9NSVdIeWhsWUh1bU9GdElPTk11QkRiQjZHZEZQQU9xZFB6?=
 =?utf-8?B?MmtUNmFxQWlkQ3dqOWdiMnA4UnVPbHVCY1J3Q1o1SnQ5dmdhcmpvWGhFVWE0?=
 =?utf-8?B?cEpZak1rMU9rOGk5V3RRanNpaVUvR1NFMDdLQk1OeVljanp2T09hdWFtUlBH?=
 =?utf-8?B?Q1FuWVRSKzhydmppQkZFdHlFcmhwbXFqdzliei9zL0ZsT0NQMDM5THVINWI4?=
 =?utf-8?B?bktYclVBQS8rVmtoak5Bd2EyNWpqcnlrVUZJS2FzQnVLTnBBOTU3V1RFOGht?=
 =?utf-8?B?MU5MNDZ4cnFSV2MwWjE5a2dTS1Z3Yk5XaU5LWlVoRDBuVmhaalpOT3VTTXNU?=
 =?utf-8?B?VExHR2hVVWYvSlYwTXpVQnZVUkJabGdSQmlON3RZd3JZSVN5dFJHZFB0cktu?=
 =?utf-8?B?empwYkl0Z25CNmZXa2luR0k5NVR5Um5QQVF0UHRrZjhONDFsbFoyWllEWHhN?=
 =?utf-8?B?a3NDbVhrVmdHVkRPNU5WSFhMNnRubTBpTGdKRGFRa1N1M0UxZTFKM0NibHds?=
 =?utf-8?B?UTQrWUNvZzd5VFpJSnhpZlhJcGlwVGpHejhqbzNJcXBwejMwekF3Wlo5TnRW?=
 =?utf-8?B?SnZBbkxsVzN6ZExDZUlld0d4NTBqaDlDalFqb0xnYVJkY05tdXB6MW02Ymkx?=
 =?utf-8?B?SFRmVERxVVV2cDFVYlVHSi9LcThoVkcvTklEMko0bWgwOTB4QnlnV1Z0bzR6?=
 =?utf-8?B?eUNUNFQwWGQ1UEdNaXRsd29ONVc4VHRUNnBFdjJxR0ZMWUFmSHF1WldEK2Zv?=
 =?utf-8?B?ejM1OTBUYktJZTZmQm0waHhpMlk4RE5XWUpaVEE5U0xubE0zQ05UOGlEaU14?=
 =?utf-8?B?OHhHU0ZVVmpHVDRmN3pIWDFRbUZFT3EwNzBPcm91ZnRHdlJEcWtnejNMZjk0?=
 =?utf-8?B?V2ZkRVZRZFgrT2Q1OHRIaDEzWVpDSmt6SlNpMmhjQW1ib3RsWHVHU0ZkN0dJ?=
 =?utf-8?B?WFZ4VmhQQ2RsZVE0TkgxODRBd2ZnZ0Fyc3BPeWJDWC96QjVUdWU5cnhSeWFE?=
 =?utf-8?B?QngwNG5ORkpkT2lldVRiME1NUXgzbUdBU0hMRzUrbnE1TmE0QXFRbzFCNURn?=
 =?utf-8?B?eTh4OWEveVpxazhmL0hOUzNURjEvVjNTdkRIdHJPb3ZUZVlzOHc1R0JBRnJh?=
 =?utf-8?B?OU9ETmxvWWlHU0g3dDdwQUlPRjFmTXo0WTNFWHFLUm5nWFhqVVM3U2UrdGFw?=
 =?utf-8?B?aUNTMkJyRytiOVBGSWpNWFk3YU9BYlQ1WWo3RHN3VDJka3NGdVB2bFJ6N01I?=
 =?utf-8?B?cDFSL3pQWlpBdWcxblZML2FkWGhFN3dmR01xQlAwREw3dkdLZC9ILzAzMnhR?=
 =?utf-8?B?WnhlZENEd0hNajl1WWNDUmFORFZaWE82aG4wd1QzcWJHeThxTVk3eUk5RDR4?=
 =?utf-8?B?TTlDWmJ5QURCaHVrM1lHL3k1QlJNQnk3MGMxWkFmQS9kd3FxRVQ2WHVEbFFX?=
 =?utf-8?Q?LauZLceWvmUNHI0dAsLlkb8=3D?=
X-OriginatorOrg: oracle.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 2a96841b-fda9-4037-2c5a-08da92aa362b
X-MS-Exchange-CrossTenant-AuthSource: CO1PR10MB4531.namprd10.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 09 Sep 2022 21:28:18.0209
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 4e2c6054-71cb-48f1-bd6c-3a9705aca71b
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: 1YB/M9tH+i54+yQMo4ol43HcTbTPdj2EsCE5845vmxbtXvvgQPBE6VolYWbTu2rmiV0lkj6cVvn8gxdGhDJ2eHyq8fyAZm/yc7RFNk+/70s=
X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS7PR10MB5149
X-Proofpoint-Virus-Version: vendor=baseguard
 engine=ICAP:2.0.205,Aquarius:18.0.895,Hydra:6.0.528,FMLib:17.11.122.1
 definitions=2022-09-09_10,2022-09-09_01,2022-06-22_01
X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 adultscore=0
 mlxlogscore=999 bulkscore=0 spamscore=0 malwarescore=0 mlxscore=0
 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1
 engine=8.12.0-2207270000 definitions=main-2209090075
X-Proofpoint-ORIG-GUID: 9Bs27g0MX6vDIHOwS6m29URK9mX4tjDE
X-Proofpoint-GUID: 9Bs27g0MX6vDIHOwS6m29URK9mX4tjDE
X-Spam-Status: No, score=-4.9 required=5.0 tests=BAYES_00,DKIM_SIGNED,
        DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,NICE_REPLY_A,RCVD_IN_DNSWL_LOW,
        RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_NONE,T_SCC_BODY_TEXT_LINE
        autolearn=ham autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
        lindbergh.monkeyblade.net
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org


On 8/30/22 22:26, Baoquan He wrote:
> On 08/26/22 at 01:37pm, Eric DeVolder wrote:
>> CPU and memory change notifications are received in order to
>> regenerate the elfcorehdr.
>>
>> To support cpu hotplug, a callback is registered to capture the
>> CPUHP_AP_ONLINE_DYN online and offline events via
>> cpuhp_setup_state_nocalls().
>>
>> To support memory hotplug, a notifier is registered to capture the
>> MEM_ONLINE and MEM_OFFLINE events via register_memory_notifier().
>>
>> The cpu callback and memory notifiers call handle_hotplug_event()
>> which performs needed tasks and then dispatches the event to the
>> architecture specific arch_crash_handle_hotplug_event(). During the
>> process, the kexec_mutex is held.
>>
>> Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
>> ---
>>   include/linux/crash_core.h |   8 +++
>>   include/linux/kexec.h      |  26 +++++++
>>   kernel/crash_core.c        | 134 +++++++++++++++++++++++++++++++++++++
>>   3 files changed, 168 insertions(+)
>>
>> diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h
>> index de62a722431e..3b99e69b011f 100644
>> --- a/include/linux/crash_core.h
>> +++ b/include/linux/crash_core.h
>> @@ -84,4 +84,12 @@ int parse_crashkernel_high(char *cmdline, unsigned long long system_ram,
>>   int parse_crashkernel_low(char *cmdline, unsigned long long system_ram,
>>   		unsigned long long *crash_size, unsigned long long *crash_base);
>>   
>> +#define KEXEC_CRASH_HP_REMOVE_CPU		0
>> +#define KEXEC_CRASH_HP_ADD_CPU			1
>> +#define KEXEC_CRASH_HP_REMOVE_MEMORY	2
>                                          ~~
>                                          Nitpick, These arenot aligned,
>> +#define KEXEC_CRASH_HP_ADD_MEMORY		3
>> +#define KEXEC_CRASH_HP_INVALID_CPU		-1U
>> +
>> +struct kimage;
>> +
>>   #endif /* LINUX_CRASH_CORE_H */
>> diff --git a/include/linux/kexec.h b/include/linux/kexec.h
>> index 4eefa631e0ae..9597b41136ec 100644
>> --- a/include/linux/kexec.h
>> +++ b/include/linux/kexec.h
>> @@ -374,6 +374,13 @@ struct kimage {
>>   	struct purgatory_info purgatory_info;
>>   #endif
>>   
>> +#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_MEMORY_HOTPLUG)
>> +	bool hotplug_event;
>> +	unsigned int offlinecpu;
>> +	bool elfcorehdr_index_valid;
>> +	int elfcorehdr_index;
>> +#endif
>> +
>>   #ifdef CONFIG_IMA_KEXEC
>>   	/* Virtual address of IMA measurement buffer for kexec syscall */
>>   	void *ima_buffer;
>> @@ -503,6 +510,25 @@ static inline int arch_kexec_post_alloc_pages(void *vaddr, unsigned int pages, g
>>   static inline void arch_kexec_pre_free_pages(void *vaddr, unsigned int pages) { }
>>   #endif
>>   
>> +#ifndef arch_map_crash_pages
>> +static inline void *arch_map_crash_pages(unsigned long paddr,
>> +		unsigned long size)
>> +{
>> +	return NULL;
>> +}
>> +#endif
>> +
>> +#ifndef arch_unmap_crash_pages
>> +static inline void arch_unmap_crash_pages(void **ptr) { }
>> +#endif
>> +
>> +#ifndef arch_crash_handle_hotplug_event
>> +static inline void arch_crash_handle_hotplug_event(struct kimage *image,
>> +		unsigned int hp_action)
>> +{
>> +}
>> +#endif
>> +
>>   #else /* !CONFIG_KEXEC_CORE */
>>   struct pt_regs;
>>   struct task_struct;
>> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
>> index 0f8aa659cca4..455150205ded 100644
>> --- a/kernel/crash_core.c
>> +++ b/kernel/crash_core.c
>> @@ -11,6 +11,8 @@
>>   #include <linux/vmalloc.h>
>>   #include <linux/sizes.h>
>>   #include <linux/kexec.h>
>> +#include <linux/memory.h>
>> +#include <linux/cpuhotplug.h>
>>   
>>   #include <asm/page.h>
>>   #include <asm/sections.h>
>> @@ -18,6 +20,7 @@
>>   #include <crypto/sha1.h>
>>   
>>   #include "kallsyms_internal.h"
>> +#include "kexec_internal.h"
>>   
>>   /* vmcoreinfo stuff */
>>   unsigned char *vmcoreinfo_data;
>> @@ -611,3 +614,134 @@ static int __init crash_save_vmcoreinfo_init(void)
>>   }
>>   
>>   subsys_initcall(crash_save_vmcoreinfo_init);
>> +
>> +#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_MEMORY_HOTPLUG)
>> +/*
>> + * To accurately reflect hot un/plug changes, the elfcorehdr (which
>> + * is passed to the crash kernel via the elfcorehdr= parameter)
>> + * must be updated with the new list of CPUs and memories.
>> + *
>> + * In order to make changes to elfcorehdr, two conditions are needed:
>> + * First, the segment containing the elfcorehdr must be large enough
>> + * to permit a growing number of resources. The elfcorehdr memory is
>> + * typically based on CONFIG_NR_CPUS and CONFIG_CRASH_MAX_MEMORY_RANGES.
>> + * Second, purgatory must explicitly exclude the elfcorehdr from the
>> + * list of segments it checks (since the elfcorehdr changes and thus
>> + * would require an update to purgatory itself to update the digest).
>> + */
>> +static void handle_hotplug_event(unsigned int hp_action, unsigned int cpu)
>> +{
>> +	/* Obtain lock while changing crash information */
>> +	mutex_lock(&kexec_mutex);
>> +
>> +	/* Check kdump is loaded */
>> +	if (kexec_crash_image) {
>> +		struct kimage *image = kexec_crash_image;
>> +
>> +		if (hp_action == KEXEC_CRASH_HP_ADD_CPU ||
>> +			hp_action == KEXEC_CRASH_HP_REMOVE_CPU)
>> +			pr_debug("crash hp: hp_action %u, cpu %u\n", hp_action, cpu);
>> +		else
>> +			pr_debug("crash hp: hp_action %u", hp_action);
>                                                         ^~ "\n" missed
>> +		/*
>> +		 * When the struct kimage is alloced, it is wiped to zero, so
>                                               ~~~~ alloced is confusing, s/alloced/allocated/
>                                              We can accept alloc being used, alloced is a little weird.
>> +		 * the elfcorehdr_index_valid defaults to false. Find the
>> +		 * segment containing the elfcorehdr, if not already found.
>> +		 * This works for both the kexec_load and kexec_file_load paths.
>> +		 */
>> +		if (!image->elfcorehdr_index_valid) {
>> +			unsigned char *ptr;
>> +			unsigned long mem, memsz;
>> +			unsigned int n;
>> +
>> +			for (n = 0; n < image->nr_segments; n++) {
>> +				mem = image->segment[n].mem;
>> +				memsz = image->segment[n].memsz;
>> +				ptr = arch_map_crash_pages(mem, memsz);
> OK, I see. You want to avoid the over 80 chars line, so introducing
> two local variables. We may be able to tolerate that in this case. No
> strong opinion, let's see if other people have concern about it.
> 
> Other than these nitpicks, this patch looks good to me.
> Acked-by: Baoquan He <bhe@redhat.com>

Baoquan, I've had no other feedback; I've corrected the items you've pointed out in this and the 
others. I've posted v12. Note that all patches in v12 now have an Acked-by!
Thanks,
eric

> 
>> +				if (ptr) {
>> +					/* The segment containing elfcorehdr */
>> +					if (memcmp(ptr, ELFMAG, SELFMAG) == 0) {
>> +						image->elfcorehdr_index = (int)n;
>> +						image->elfcorehdr_index_valid = true;
>> +					}
>> +				}
>> +				arch_unmap_crash_pages((void **)&ptr);
>> +			}
>> +		}
>> +
>> +		if (!image->elfcorehdr_index_valid) {
>> +			pr_err("crash hp: unable to locate elfcorehdr segment");
>> +			goto out;
>> +		}
>> +
>> +		/* Needed in order for the segments to be updated */
>> +		arch_kexec_unprotect_crashkres();
>> +
>> +		/* Flag to differentiate between normal load and hotplug */
>> +		image->hotplug_event = true;
>> +
>> +		/* Now invoke arch-specific update handler */
>> +		arch_crash_handle_hotplug_event(image, hp_action);
>> +
>> +		/* No longer handling a hotplug event */
>> +		image->hotplug_event = false;
>> +
>> +		/* Change back to read-only */
>> +		arch_kexec_protect_crashkres();
>> +	}
>> +
>> +out:
>> +	/* Release lock now that update complete */
>> +	mutex_unlock(&kexec_mutex);
>> +}
>> +
>> +static int crash_memhp_notifier(struct notifier_block *nb, unsigned long val, void *v)
>> +{
>> +	switch (val) {
>> +	case MEM_ONLINE:
>> +		handle_hotplug_event(KEXEC_CRASH_HP_ADD_MEMORY, 0);
>> +		break;
>> +
>> +	case MEM_OFFLINE:
>> +		handle_hotplug_event(KEXEC_CRASH_HP_REMOVE_MEMORY, 0);
>> +		break;
>> +	}
>> +	return NOTIFY_OK;
>> +}
>> +
>> +static struct notifier_block crash_memhp_nb = {
>> +	.notifier_call = crash_memhp_notifier,
>> +	.priority = 0
>> +};
>> +
>> +static int crash_cpuhp_online(unsigned int cpu)
>> +{
>> +	handle_hotplug_event(KEXEC_CRASH_HP_ADD_CPU, cpu);
>> +	return 0;
>> +}
>> +
>> +static int crash_cpuhp_offline(unsigned int cpu)
>> +{
>> +	handle_hotplug_event(KEXEC_CRASH_HP_REMOVE_CPU, cpu);
>> +	return 0;
>> +}
>> +
>> +static int __init crash_hotplug_init(void)
>> +{
>> +	int result = 0;
>> +
>> +	if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG))
>> +		register_memory_notifier(&crash_memhp_nb);
>> +
>> +	if (IS_ENABLED(CONFIG_HOTPLUG_CPU))
>> +		result = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
>> +						   "crash/cpuhp",
>> +						   crash_cpuhp_online,
>> +						   crash_cpuhp_offline);
>> +
>> +	return result;
>> +}
>> +
>> +subsys_initcall(crash_hotplug_init);
>> +#endif
>> -- 
>> 2.31.1
>>
>