On Fri, Sep 30, 2022 at 10:36:49AM -0500, Eric DeVolder wrote:
> > Your help text talks about System RAM entries in /proc/iomem which means
> > that those entries are present somewhere in the kernel and you can read
> > them out and do the proper calculations dynamically instead of doing the
> > static CONFIG_NR_CPUS_DEFAULT + CONFIG_CRASH_MAX_MEMORY_RANGES thing.
>
> The intent is to compute the max size buffer needed to contain a maximum
> populated elfcorehdr, which is primarily based on the number of CPUs and
> memory regions. Thus far I (and others involved) have not found a kernel
> method to determine the maximum number of memory regions possible (if you
> are aware of one, please let me know!). Thus CONFIG_CRASH_MAX_MEMORY_RANGES
> was born (rather borrowed from kexec-tools).
Let's ask some mm folks.
mm folks, is there a way to enumerate all the memory regions a machine
has?
It looks to me like register_memory_resource() in mm/memory_hotplug.c
does register the resource so there should be a way to count that list
of resources or at least maintain a count somewhere so that kexec/crash
code can know how big its elfcodehdr buffer should be instead of doing a
clumsy Kconfig item where people would need to guess...
Hmm.
> > +#ifdef CONFIG_CRASH_MAX_MEMORY_RANGES
> So I think the use of CONFIG_CRASH_MAX_MEMORY_RANGES is not correct; it
> still needs to be based on the cpu or memory hotplug options.
You're kidding, right?
+config CRASH_MAX_MEMORY_RANGES
+ depends on CRASH_DUMP && KEXEC_FILE && (HOTPLUG_CPU || MEMORY_HOTPLUG)
^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> > @@ -622,6 +622,15 @@ static int __init crash_save_vmcoreinfo_init(void)
> > subsys_initcall(crash_save_vmcoreinfo_init);
> > #if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_MEMORY_HOTPLUG)
> > +
> > +void __weak *arch_map_crash_pages(unsigned long paddr, unsigned long size)
> > +{
> > + return NULL;
> > +}
> > +
> > +void __weak arch_unmap_crash_pages(void **ptr) { }
> > +void __weak arch_crash_handle_hotplug_event(struct kimage *image, unsigned int hp_action) { }
> > +
> I was asked by Baoquan He to eliminate the use of __weak
Because?
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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