On 23/04/2023 12:52:12, Sourabh Jain wrote:
> On PowePC memblock regions are used to prepare elfcorehdr which
> describes the memory regions of the running kernel to the kdump kernel.
> Since the notifier used for the memory hotplug crash handler gets
> initiated before the update of the memblock region happens (as depicted
> below) the newly prepared elfcorehdr still holds the old memory regions.
> If the elfcorehdr is prepared with stale memblock regions then the newly
> prepared elfcorehdr will still be holding stale memory regions. And dump
> collection with stale elfcorehdr will lead to dump collection failure or
> incomplete dump collection.
>
> The sequence of actions done on PowerPC when an LMB memory hot removed:
>
> Initiate memory hot remove
> |
> v
> offline pages
> |
> v
> initiate memory notify call
> chain for MEM_OFFLINE event <---> Prepare new elfcorehdr and replace
> it with old one
> |
> v
> update memblock regions
>
> Such challenges only exist for memory remove case. For the memory add
> case the memory regions are updated first and then memory notify calls
> the arch crash hotplug handler to update the elfcorehdr.
>
> This patch passes additional information about the hot removed LMB to
> the arch crash hotplug handler in the form of memory_notify object.
>
> How passing memory_notify to arch crash hotplug handler will help?
>
> memory_notify holds the start PFN and page count of the hot removed
> memory. With that base address and the size of the hot removed memory
> can be calculated and same can be used to avoid adding hot removed
> memory region to get added in the elfcorehdr.
>
> Signed-off-by: Sourabh Jain <sourabhjain@xxxxxxxxxxxxx>
> Reviewed-by: Laurent Dufour <laurent.dufour@xxxxxxxxxx>
I don't remember sending a review-by on this patch earlier, do you?
> ---
> arch/powerpc/include/asm/kexec.h | 2 +-
> arch/powerpc/kexec/core_64.c | 3 ++-
> arch/x86/include/asm/kexec.h | 2 +-
> arch/x86/kernel/crash.c | 3 ++-
> include/linux/kexec.h | 2 +-
> kernel/crash_core.c | 14 +++++++-------
> 6 files changed, 14 insertions(+), 12 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/kexec.h b/arch/powerpc/include/asm/kexec.h
> index f01ba767af56e..7e811bad5ec92 100644
> --- a/arch/powerpc/include/asm/kexec.h
> +++ b/arch/powerpc/include/asm/kexec.h
> @@ -104,7 +104,7 @@ struct crash_mem;
> int update_cpus_node(void *fdt);
> int get_crash_memory_ranges(struct crash_mem **mem_ranges);
> #if defined(CONFIG_CRASH_HOTPLUG)
> -void arch_crash_handle_hotplug_event(struct kimage *image);
> +void arch_crash_handle_hotplug_event(struct kimage *image, void *arg);
> #define arch_crash_handle_hotplug_event arch_crash_handle_hotplug_event
> #endif
> #endif
> diff --git a/arch/powerpc/kexec/core_64.c b/arch/powerpc/kexec/core_64.c
> index 611b89bcea2be..147ea6288a526 100644
> --- a/arch/powerpc/kexec/core_64.c
> +++ b/arch/powerpc/kexec/core_64.c
> @@ -551,10 +551,11 @@ int update_cpus_node(void *fdt)
> * arch_crash_hotplug_handler() - Handle crash CPU/Memory hotplug events to update the
> * necessary kexec segments based on the hotplug event.
> * @image: the active struct kimage
> + * @arg: struct memory_notify handler for memory add/remove case and NULL for CPU case.
> *
> * Update FDT segment to include newly added CPU. No action for CPU remove case.
> */
> -void arch_crash_handle_hotplug_event(struct kimage *image)
> +void arch_crash_handle_hotplug_event(struct kimage *image, void *arg)
> {
> void *fdt, *ptr;
> unsigned long mem;
> diff --git a/arch/x86/include/asm/kexec.h b/arch/x86/include/asm/kexec.h
> index 1bc852ce347d4..70c3b23b468b6 100644
> --- a/arch/x86/include/asm/kexec.h
> +++ b/arch/x86/include/asm/kexec.h
> @@ -213,7 +213,7 @@ extern crash_vmclear_fn __rcu *crash_vmclear_loaded_vmcss;
> extern void kdump_nmi_shootdown_cpus(void);
>
> #ifdef CONFIG_CRASH_HOTPLUG
> -void arch_crash_handle_hotplug_event(struct kimage *image);
> +void arch_crash_handle_hotplug_event(struct kimage *image, void *arg);
> #define arch_crash_handle_hotplug_event arch_crash_handle_hotplug_event
>
> #ifdef CONFIG_HOTPLUG_CPU
> diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
> index ead602636f3e0..b45d13193b579 100644
> --- a/arch/x86/kernel/crash.c
> +++ b/arch/x86/kernel/crash.c
> @@ -445,11 +445,12 @@ int crash_load_segments(struct kimage *image)
> /**
> * arch_crash_handle_hotplug_event() - Handle hotplug elfcorehdr changes
> * @image: the active struct kimage
> + * @arg: struct memory_notify handler for memory add/remove case and NULL for CPU case.
> *
> * The new elfcorehdr is prepared in a kernel buffer, and then it is
> * written on top of the existing/old elfcorehdr.
> */
> -void arch_crash_handle_hotplug_event(struct kimage *image)
> +void arch_crash_handle_hotplug_event(struct kimage *image, void *arg)
> {
> void *elfbuf = NULL, *old_elfcorehdr;
> unsigned long nr_mem_ranges;
> diff --git a/include/linux/kexec.h b/include/linux/kexec.h
> index 0ac41f48de0b1..69765e6a92d0d 100644
> --- a/include/linux/kexec.h
> +++ b/include/linux/kexec.h
> @@ -506,7 +506,7 @@ static inline void arch_kexec_pre_free_pages(void *vaddr, unsigned int pages) {
> #endif
>
> #ifndef arch_crash_handle_hotplug_event
> -static inline void arch_crash_handle_hotplug_event(struct kimage *image) { }
> +static inline void arch_crash_handle_hotplug_event(struct kimage *image, void *arg) { }
> #endif
>
> #ifndef crash_hotplug_cpu_support
> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
> index 4aa3c7a6b390f..7afe5f60d2bfe 100644
> --- a/kernel/crash_core.c
> +++ b/kernel/crash_core.c
> @@ -718,7 +718,7 @@ subsys_initcall(crash_save_vmcoreinfo_init);
> * list of segments it checks (since the elfcorehdr changes and thus
> * would require an update to purgatory itself to update the digest).
> */
> -static void crash_handle_hotplug_event(unsigned int hp_action, unsigned int cpu)
> +static void crash_handle_hotplug_event(unsigned int hp_action, unsigned int cpu, void *arg)
> {
> struct kimage *image;
>
> @@ -775,7 +775,7 @@ static void crash_handle_hotplug_event(unsigned int hp_action, unsigned int cpu)
> image->hp_action = hp_action;
>
> /* Now invoke arch-specific update handler */
> - arch_crash_handle_hotplug_event(image);
> + arch_crash_handle_hotplug_event(image, arg);
>
> /* No longer handling a hotplug event */
> image->hp_action = KEXEC_CRASH_HP_NONE;
> @@ -789,17 +789,17 @@ static void crash_handle_hotplug_event(unsigned int hp_action, unsigned int cpu)
> kexec_unlock();
> }
>
> -static int crash_memhp_notifier(struct notifier_block *nb, unsigned long val, void *v)
> +static int crash_memhp_notifier(struct notifier_block *nb, unsigned long val, void *arg)
> {
> switch (val) {
> case MEM_ONLINE:
> crash_handle_hotplug_event(KEXEC_CRASH_HP_ADD_MEMORY,
> - KEXEC_CRASH_HP_INVALID_CPU);
> + KEXEC_CRASH_HP_INVALID_CPU, arg);
> break;
>
> case MEM_OFFLINE:
> crash_handle_hotplug_event(KEXEC_CRASH_HP_REMOVE_MEMORY,
> - KEXEC_CRASH_HP_INVALID_CPU);
> + KEXEC_CRASH_HP_INVALID_CPU, arg);
> break;
> }
> return NOTIFY_OK;
> @@ -812,13 +812,13 @@ static struct notifier_block crash_memhp_nb = {
>
> static int crash_cpuhp_online(unsigned int cpu)
> {
> - crash_handle_hotplug_event(KEXEC_CRASH_HP_ADD_CPU, cpu);
> + crash_handle_hotplug_event(KEXEC_CRASH_HP_ADD_CPU, cpu, NULL);
> return 0;
> }
>
> static int crash_cpuhp_offline(unsigned int cpu)
> {
> - crash_handle_hotplug_event(KEXEC_CRASH_HP_REMOVE_CPU, cpu);
> + crash_handle_hotplug_event(KEXEC_CRASH_HP_REMOVE_CPU, cpu, NULL);
> return 0;
> }
>
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