From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sourabh Jain Date: Thu, 28 Apr 2022 10:48:50 +0530 Subject: [PATCH v7 4/8] crash: add generic infrastructure for crash hotplug support In-Reply-To: References: <20220413164237.20845-1-eric.devolder@oracle.com> <20220413164237.20845-5-eric.devolder@oracle.com> <4eea2373-32f3-9960-cbec-21dc1a428807@oracle.com> <6f3a6cbb-0ac4-f178-fc17-18f9594da319@linux.ibm.com> Message-ID: List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: kexec@lists.infradead.org Hi Baoquan, On 26/04/22 10:52, Baoquan He wrote: > On 04/26/22 at 09:36am, Sourabh Jain wrote: >> On 15/04/22 03:59, Eric DeVolder wrote: >>> Hi Baoquan, >>> Inline comments below. >>> Thanks! >>> eric >>> >>> On 4/13/22 21:45, Baoquan He wrote: >>>> On 04/13/22 at 12:42pm, Eric DeVolder wrote: >>>>> Upon CPU and memory changes, a generic crash_hotplug_handler() >>>>> dispatches the hot plug/unplug event to the architecture specific >>>>> arch_crash_hotplug_handler(). During the process, the kexec_mutex >>>>> is held. >>>>> >>>>> To support cpu hotplug, a callback is registered to capture the >>>>> CPUHP_AP_ONLINE_DYN online and ofline 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 notifier then call crash_hotplug_handler() >>>>> to handle the hot plug/unplug event. >>>>> >>>>> Signed-off-by: Eric DeVolder >>>>> --- >>>>> ? include/linux/kexec.h |? 16 +++++++ >>>>> ? kernel/crash_core.c?? | 101 >>>>> ++++++++++++++++++++++++++++++++++++++++++ >>>>> ? 2 files changed, 117 insertions(+) >>>>> >>>>> diff --git a/include/linux/kexec.h b/include/linux/kexec.h >>>>> index f93f2591fc1e..02daff1f47dd 100644 >>>>> --- a/include/linux/kexec.h >>>>> +++ b/include/linux/kexec.h >>>>> @@ -306,6 +306,13 @@ struct kimage { >>>>> ? ????? /* Information for loading purgatory */ >>>>> ????? struct purgatory_info purgatory_info; >>>>> + >>>>> +#ifdef CONFIG_CRASH_HOTPLUG >>>>> +??? bool hotplug_event; >>>>> +??? unsigned int offlinecpu; >>>>> +??? bool elfcorehdr_index_valid; >>>>> +??? int elfcorehdr_index; >>>>> +#endif >>>>> ? #endif >>>>> ? ? #ifdef CONFIG_IMA_KEXEC >>>>> @@ -322,6 +329,15 @@ struct kimage { >>>>> ????? unsigned long elf_load_addr; >>>>> ? }; >>>>> ? +#ifdef CONFIG_CRASH_HOTPLUG >>>>> +void arch_crash_hotplug_handler(struct kimage *image, >>>>> +??? unsigned int hp_action, unsigned int cpu); >>>>> +#define KEXEC_CRASH_HP_REMOVE_CPU?? 0 >>>>> +#define KEXEC_CRASH_HP_ADD_CPU????? 1 >>>>> +#define KEXEC_CRASH_HP_REMOVE_MEMORY 2 >>>>> +#define KEXEC_CRASH_HP_ADD_MEMORY?? 3 >>>>> +#endif /* CONFIG_CRASH_HOTPLUG */ >>>>> + >>>>> ? /* kexec interface functions */ >>>>> ? extern void machine_kexec(struct kimage *image); >>>>> ? extern int machine_kexec_prepare(struct kimage *image); >>>>> diff --git a/kernel/crash_core.c b/kernel/crash_core.c >>>>> index 256cf6db573c..ecf746243ab2 100644 >>>>> --- a/kernel/crash_core.c >>>>> +++ b/kernel/crash_core.c >>>>> @@ -9,12 +9,17 @@ >>>>> ? #include >>>>> ? #include >>>>> ? #include >>>>> +#include >>>>> +#include >>>>> +#include >>>>> ? ? #include >>>>> ? #include >>>>> ? ? #include >>>>> ? +#include "kexec_internal.h" >>>>> + >>>>> ? /* vmcoreinfo stuff */ >>>>> ? unsigned char *vmcoreinfo_data; >>>>> ? size_t vmcoreinfo_size; >>>>> @@ -491,3 +496,99 @@ static int __init crash_save_vmcoreinfo_init(void) >>>>> ? } >>>>> ? ? subsys_initcall(crash_save_vmcoreinfo_init); >>>>> + >>>>> +#ifdef CONFIG_CRASH_HOTPLUG >>>>> +void __weak arch_crash_hotplug_handler(struct kimage *image, >>>>> +??? unsigned int hp_action, unsigned int cpu) >>>>> +{ >>>>> +??? pr_warn("crash hp: %s not implemented", __func__); >>>>> +} >>>>> + >>>>> +static void crash_hotplug_handler(unsigned int hp_action, >>>>> +??? unsigned int cpu) >>>>> +{ >>>>> +??? /* Obtain lock while changing crash information */ >>>>> +??? if (!mutex_trylock(&kexec_mutex)) >>>>> +??????? return; >>>>> + >>>>> +??? /* Check kdump is loaded */ >>>>> +??? if (kexec_crash_image) { >>>>> +??????? pr_debug("crash hp: hp_action %u, cpu %u", hp_action, cpu); >>>>> + >>>>> +??????? /* Needed in order for the segments to be updated */ >>>>> +??????? arch_kexec_unprotect_crashkres(); >>>>> + >>>>> +??????? /* Flag to differentiate between normal load and hotplug */ >>>>> +??????? kexec_crash_image->hotplug_event = true; >>>>> + >>>>> +??????? /* Now invoke arch-specific update handler */ >>>>> +??????? arch_crash_hotplug_handler(kexec_crash_image, hp_action, cpu); >>>>> + >>>>> +??????? /* No longer handling a hotplug event */ >>>>> +??????? kexec_crash_image->hotplug_event = false; >>>>> + >>>>> +??????? /* Change back to read-only */ >>>>> +??????? arch_kexec_protect_crashkres(); >>>>> +??? } >>>>> + >>>>> +??? /* Release lock now that update complete */ >>>>> +??? mutex_unlock(&kexec_mutex); >>>>> +} >>>>> + >>>>> +#if defined(CONFIG_MEMORY_HOTPLUG) >>>>> +static int crash_memhp_notifier(struct notifier_block *nb, >>>>> +??? unsigned long val, void *v) >>>>> +{ >>>>> +??? struct memory_notify *mhp = v; >>>>> + >>>>> +??? switch (val) { >>>>> +??? case MEM_ONLINE: >>>>> +??????? crash_hotplug_handler(KEXEC_CRASH_HP_ADD_MEMORY, -1U); >>>> We don't differentiate the memory add/remove, cpu add, except of cpu >>>> remove. Means the hp_action only differentiate cpu remove from the other >>>> action. Maybe only making two types? >>>> >>>> #define KEXEC_CRASH_HP_REMOVE_CPU?? 0 >>>> #define KEXEC_CRASH_HP_UPDATE_OTHER????? 1 >>>> >>> Sourabh Jain's work with PPC uses REMOVE_CPU, REMOVE_MEMORY, and >>> ADD_MEMORY. >>> Do you still want to consolidate these? >> On PowerPC different actions are needed for CPU add and memory add/remove. >> For CPU add case only FDT is updated whereas for the memory hotplug we will >> be >> updating FDT and elfcorehdr. > I don't understand. For elfcorehdr updating, we only need regenerate it. > Do you update them different for memory add/remove? We have different actions for cpu remove, CPU add and memory add/remove case. CPU remove: no action CPU add: update flattened device tree (FDT) memory add/remove: update FDT and regenerate/update elfcorehdr Since memory add/remove action is same we can have common hp_action for them. > > What I saw is the added action for memory hotplug is only for message > printing. Is this really needed? And memory hotplug is even not > supported. Please correct me if I missed anything. I agree that currently memory hp_action is only used for printing warning message but eventually we will be handling memory hotplug case as well. > + /* crash update on memory hotplug is not support yet */ > + if (hp_action == KEXEC_CRASH_HP_REMOVE_MEMORY || hp_action == KEXEC_CRASH_HP_ADD_MEMORY) { > + pr_info_once("crash hp: crash update is not supported with memory hotplug\n"); > + return; > + } Thanks, Sourabh Jain