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
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