On 03/26/20 at 06:07pm, James Morse wrote:
> Memory added to the system by hotplug has a 'System RAM' resource created
> for it. This is exposed to user-space via /proc/iomem.
>
> This poses problems for kexec on arm64. If kexec decides to place the
> kernel in one of these newly onlined regions, the new kernel will find
> itself booting from a region not described as memory in the firmware
> tables.
>
> Arm64 doesn't have a structure like the e820 memory map that can be
> re-written when memory is brought online. Instead arm64 uses the UEFI
> memory map, or the memory node from the DT, sometimes both. We never
> rewrite these.
Could arm64 use similar way to update DT, or a cooked UEFI maps?
Add pingfan in cc, he said ppc64 update the DT after a memremove thus it
would be good to just redo a kexec load.
Added Pingfan and Hari for comments and corrections.
>
> Allow an architecture to specify a different name for these hotplug
> regions.
>
> Signed-off-by: James Morse <james.morse@xxxxxxx>
> ---
> mm/memory_hotplug.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 0a54ffac8c68..69b03dd7fc74 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -42,6 +42,10 @@
> #include "internal.h"
> #include "shuffle.h"
>
> +#ifndef MEMORY_HOTPLUG_RES_NAME
> +#define MEMORY_HOTPLUG_RES_NAME "System RAM"
> +#endif
> +
> /*
> * online_page_callback contains pointer to current page onlining function.
> * Initially it is generic_online_page(). If it is required it could be
> @@ -103,7 +107,7 @@ static struct resource *register_memory_resource(u64 start, u64 size)
> {
> struct resource *res;
> unsigned long flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
> - char *resource_name = "System RAM";
> + char *resource_name = MEMORY_HOTPLUG_RES_NAME;
>
> if (start + size > max_mem_size)
> return ERR_PTR(-E2BIG);
> --
> 2.25.1
>
>
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