[PATCH v14 2/6] crash: make CPU and Memory hotplug support reporting flexible
Sourabh Jain
sourabhjain at linux.ibm.com
Thu Dec 14 21:46:31 PST 2023
Hello Baoquan,
On 14/12/23 19:43, Baoquan He wrote:
> On 12/11/23 at 02:00pm, Sourabh Jain wrote:
>> Architectures' specific functions `arch_crash_hotplug_cpu_support()` and
>> `arch_crash_hotplug_memory_support()` advertise the kernel's capability
>> to update the kdump image on CPU and Memory hotplug events to userspace
>> via the sysfs interface. These architecture-specific functions need to
>> access various attributes of the `kexec_crash_image` object to determine
>> whether the kernel can update the kdump image and advertise this
>> information to userspace accordingly.
>>
>> As the architecture-specific code is not exposed to the APIs required to
>> acquire the lock for accessing the `kexec_crash_image` object, it calls
>> a generic function, `crash_check_update_elfcorehdr()`, to determine
>> whether the kernel can update the kdump image or not.
>>
>> The lack of access to the `kexec_crash_image` object in
>> architecture-specific code restricts architectures from performing
>> additional architecture-specific checks required to determine if the
>> kdump image is updatable or not. For instance, on PowerPC, the kernel
>> can update the kdump image only if both the elfcorehdr and FDT are
>> marked as updatable for the `kexec_load` system call.
>>
>> So define two generic functions, `crash_hotplug_cpu_support()` and
>> `crash_hotplug_memory_support()`, which are called when userspace
>> attempts to read the crash CPU and Memory hotplug support via the sysfs
>> interface. These functions take the necessary locks needed to access the
>> `kexec_crash_image` object and then forward it to the
>> architecture-specific handler to do the rest.
>>
>> Signed-off-by: Sourabh Jain <sourabhjain at linux.ibm.com>
>> Cc: Akhil Raj <lf32.dev at gmail.com>
>> Cc: Andrew Morton <akpm at linux-foundation.org>
>> Cc: Aneesh Kumar K.V <aneesh.kumar at kernel.org>
>> Cc: Baoquan He <bhe at redhat.com>
>> Cc: Borislav Petkov (AMD) <bp at alien8.de>
>> Cc: Boris Ostrovsky <boris.ostrovsky at oracle.com>
>> Cc: Christophe Leroy <christophe.leroy at csgroup.eu>
>> Cc: Dave Hansen <dave.hansen at linux.intel.com>
>> Cc: Dave Young <dyoung at redhat.com>
>> Cc: David Hildenbrand <david at redhat.com>
>> Cc: Eric DeVolder <eric.devolder at oracle.com>
>> Cc: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
>> Cc: Hari Bathini <hbathini at linux.ibm.com>
>> Cc: Laurent Dufour <laurent.dufour at fr.ibm.com>
>> Cc: Mahesh Salgaonkar <mahesh at linux.ibm.com>
>> Cc: Michael Ellerman <mpe at ellerman.id.au>
>> Cc: Mimi Zohar <zohar at linux.ibm.com>
>> Cc: Naveen N Rao <naveen at kernel.org>
>> Cc: Oscar Salvador <osalvador at suse.de>
>> Cc: Thomas Gleixner <tglx at linutronix.de>
>> Cc: Valentin Schneider <vschneid at redhat.com>
>> Cc: Vivek Goyal <vgoyal at redhat.com>
>> Cc: kexec at lists.infradead.org
>> Cc: x86 at kernel.org
>> ---
>> arch/x86/include/asm/kexec.h | 8 ++++----
>> arch/x86/kernel/crash.c | 20 +++++++++++++++-----
>> include/linux/kexec.h | 13 +++++++------
>> kernel/crash_core.c | 23 +++++++++++++++++------
>> 4 files changed, 43 insertions(+), 21 deletions(-)
>>
>> diff --git a/arch/x86/include/asm/kexec.h b/arch/x86/include/asm/kexec.h
>> index 9bb6607e864e..5c88d27b086d 100644
>> --- a/arch/x86/include/asm/kexec.h
>> +++ b/arch/x86/include/asm/kexec.h
>> @@ -212,13 +212,13 @@ 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
>> -int arch_crash_hotplug_cpu_support(void);
>> -#define crash_hotplug_cpu_support arch_crash_hotplug_cpu_support
>> +int arch_crash_hotplug_cpu_support(struct kimage *image);
>> +#define arch_crash_hotplug_cpu_support arch_crash_hotplug_cpu_support
>> #endif
>>
>> #ifdef CONFIG_MEMORY_HOTPLUG
>> -int arch_crash_hotplug_memory_support(void);
>> -#define crash_hotplug_memory_support arch_crash_hotplug_memory_support
>> +int arch_crash_hotplug_memory_support(struct kimage *image);
>> +#define arch_crash_hotplug_memory_support arch_crash_hotplug_memory_support
>> #endif
>>
>> unsigned int arch_crash_get_elfcorehdr_size(void);
>> diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
>> index 0d7b2657beb6..ad5941665589 100644
>> --- a/arch/x86/kernel/crash.c
>> +++ b/arch/x86/kernel/crash.c
>> @@ -398,18 +398,28 @@ int crash_load_segments(struct kimage *image)
>> #undef pr_fmt
>> #define pr_fmt(fmt) "crash hp: " fmt
>>
>> -/* These functions provide the value for the sysfs crash_hotplug nodes */
>> +#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_MEMORY_HOTPLUG)
>> +static int crash_hotplug_support(struct kimage *image)
>> +{
>> + if (image->file_mode)
>> + return 1;
>> +
>> + return image->update_elfcorehdr;
>> +}
>> +#endif
>> +
>> #ifdef CONFIG_HOTPLUG_CPU
>> -int arch_crash_hotplug_cpu_support(void)
>> +/* These functions provide the value for the sysfs crash_hotplug nodes */
>> +int arch_crash_hotplug_cpu_support(struct kimage *image)
>> {
>> - return crash_check_update_elfcorehdr();
>> + return crash_hotplug_support(image);
>> }
>> #endif
>>
>> #ifdef CONFIG_MEMORY_HOTPLUG
>> -int arch_crash_hotplug_memory_support(void)
>> +int arch_crash_hotplug_memory_support(struct kimage *image)
>> {
>> - return crash_check_update_elfcorehdr();
>> + return crash_hotplug_support(image);
>> }
>> #endif
>>
>> diff --git a/include/linux/kexec.h b/include/linux/kexec.h
>> index ee28c09a7fb0..0f6ea35879ee 100644
>> --- a/include/linux/kexec.h
>> +++ b/include/linux/kexec.h
>> @@ -486,16 +486,17 @@ static inline void arch_kexec_pre_free_pages(void *vaddr, unsigned int pages) {
>> static inline void arch_crash_handle_hotplug_event(struct kimage *image, void *arg) { }
>> #endif
>>
>> -int crash_check_update_elfcorehdr(void);
>> -
>> -#ifndef crash_hotplug_cpu_support
>> -static inline int crash_hotplug_cpu_support(void) { return 0; }
>> +#ifndef arch_crash_hotplug_cpu_support
>> +static inline int arch_crash_hotplug_cpu_support(struct kimage *image) { return 0; }
>> #endif
>>
>> -#ifndef crash_hotplug_memory_support
>> -static inline int crash_hotplug_memory_support(void) { return 0; }
>> +#ifndef arch_crash_hotplug_memory_support
>> +static inline int arch_crash_hotplug_memory_support(struct kimage *image) { return 0; }
>> #endif
>>
>> +extern int crash_hotplug_cpu_support(void);
>> +extern int crash_hotplug_memory_support(void);
>> +
>> #ifndef crash_get_elfcorehdr_size
>> static inline unsigned int crash_get_elfcorehdr_size(void) { return 0; }
>> #endif
>> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
>> index b9190265fe52..b621f03c1104 100644
>> --- a/kernel/crash_core.c
>> +++ b/kernel/crash_core.c
>> @@ -892,12 +892,14 @@ DEFINE_MUTEX(__crash_hotplug_lock);
>> #define crash_hotplug_lock() mutex_lock(&__crash_hotplug_lock)
>> #define crash_hotplug_unlock() mutex_unlock(&__crash_hotplug_lock)
>>
>> +#define CPU_HOTPLUG 0
>> +#define MEM_HOTPLUG 1
>> /*
>> * This routine utilized when the crash_hotplug sysfs node is read.
>> * It reflects the kernel's ability/permission to update the crash
>> * elfcorehdr directly.
>> */
>> -int crash_check_update_elfcorehdr(void)
>> +static int crash_hotplug_support(int hotplug)
> Is it possible that we rename this function to different name? e.g
> crash_hotplug_check_support() or other name. We may easily mixing it up
> with the one of ARCH version. personal opinion
Sure I will rename the common function to crash_hotplug_check_support()
and arch-specific function to arch_crash_hotplug_check_support.
Thanks,
Sourabh
>
>> {
>> int rc = 0;
>>
>> @@ -909,18 +911,27 @@ int crash_check_update_elfcorehdr(void)
>> return 0;
>> }
>> if (kexec_crash_image) {
>> - if (kexec_crash_image->file_mode)
>> - rc = 1;
>> - else
>> - rc = kexec_crash_image->update_elfcorehdr;
>> + if (hotplug == CPU_HOTPLUG)
>> + rc = arch_crash_hotplug_cpu_support(kexec_crash_image);
>> + else if (hotplug == MEM_HOTPLUG)
>> + rc = arch_crash_hotplug_memory_support(kexec_crash_image);
>> }
>> /* Release lock now that update complete */
>> kexec_unlock();
>> crash_hotplug_unlock();
>> -
>> return rc;
>> }
>>
>> +int crash_hotplug_cpu_support(void)
>> +{
>> + return crash_hotplug_support(CPU_HOTPLUG);
>> +}
>> +
>> +int crash_hotplug_memory_support(void)
>> +{
>> + return crash_hotplug_support(MEM_HOTPLUG);
>> +}
>> +
>> /*
>> * To accurately reflect hot un/plug changes of cpu and memory resources
>> * (including onling and offlining of those resources), the elfcorehdr
>> --
>> 2.41.0
>>
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