From mboxrd@z Thu Jan 1 00:00:00 1970 From: Baoquan He Date: Tue, 26 Apr 2022 13:22:22 +0800 Subject: [PATCH v7 4/8] crash: add generic infrastructure for crash hotplug support In-Reply-To: <6f3a6cbb-0ac4-f178-fc17-18f9594da319@linux.ibm.com> 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 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? 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. + /* 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; + } > > Ideally, I would prefer the crash hotplug handler to report all four actions > separately. > > Thanks, > Sourabh Jain >