Re: [PATCH 3/3] arm64: memory: Give hotplug memory a different resource name

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On 26.03.20 19:07, James Morse wrote:
> If kexec chooses to place the kernel in a memory region that was
> added after boot, we fail to boot as the kernel is running from a
> location that is not described as memory by the UEFI memory map or
> the original DT.
> 
> To prevent unaware user-space kexec from doing this accidentally,
> give these regions a different name.
> 
> Signed-off-by: James Morse <james.morse@xxxxxxx>
> ---
> This is a change in behaviour as seen by user-space, because memory hot-add
> has already been merged.
> 
>  arch/arm64/include/asm/memory.h | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
> index 2be67b232499..ef1686518469 100644
> --- a/arch/arm64/include/asm/memory.h
> +++ b/arch/arm64/include/asm/memory.h
> @@ -166,6 +166,17 @@
>  #define IOREMAP_MAX_ORDER	(PMD_SHIFT)
>  #endif
>  
> +/*
> + * Memory hotplug allows new regions of 'System RAM' to be added to the system.
> + * These aren't described as memory by the UEFI memory map, or DT memory node.
> + * If we kexec from one of these regions, the new kernel boots from a location
> + * that isn't described as RAM.
> + *
> + * Give these resources a different name, so unaware kexec doesn't do this by
> + * accident.
> + */
> +#define MEMORY_HOTPLUG_RES_NAME "System RAM (hotplug)"
> +
>  #ifndef __ASSEMBLY__
>  extern u64			vabits_actual;
>  #define PAGE_END		(_PAGE_END(vabits_actual))
> 

(While I am familiar with makedumpfile in the crash kernel, I am not yet
familiar with kexec, so bare with me)


Looking at kexec:arch/arm64/crashdump-arm64.c

load_crashdump_segments() -> crash_get_memory_ranges() ->
kexec_iomem_for_each_line() -> iomem_range_callback()


#define SYSTEM_RAM "System RAM\n"

...
} else if (strncmp(str, SYSTEM_RAM, strlen(SYSTEM_RAM)) == 0) {
	return mem_regions_add(&system_memory_rgns, ...);
}


The hotplugged memory will no longer be detected as a crashdump segment,
consequently (AFAIU) not be described in the elf header, and therefore
also no longer dumped (e.g., by makedumpfile).

I assume you'll have to adapt kexec-tools to still consider this memory
for dumping, correct? Or am I missing something?


-- 
Thanks,

David / dhildenb


_______________________________________________
kexec mailing list
kexec@xxxxxxxxxxxxxxxxxxx
http://lists.infradead.org/mailman/listinfo/kexec



[Index of Archives]     [LM Sensors]     [Linux Sound]     [ALSA Users]     [ALSA Devel]     [Linux Audio Users]     [Linux Media]     [Kernel]     [Gimp]     [Yosemite News]     [Linux Media]

  Powered by Linux