On 09.05.20 02:45, Andrew Morton wrote:
> On Thu, 26 Mar 2020 18:07:29 +0000 James Morse <james.morse@xxxxxxx> 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.
>>
>> Allow an architecture to specify a different name for these hotplug
>> regions.
>>
>> ...
>>
>> --- 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);
>
> I suppose we should do this as well:
>
> --- a/mm/memory_hotplug.c~mm-memory_hotplug-allow-arch-override-of-non-boot-memory-resource-names-fix
> +++ a/mm/memory_hotplug.c
> @@ -129,7 +129,8 @@ static struct resource *register_memory_
> resource_name, flags);
>
> if (!res) {
> - pr_debug("Unable to reserve System RAM region: %016llx->%016llx\n",
> + pr_debug("Unable to reserve " MEMORY_HOTPLUG_RES_NAME
> + " region: %016llx->%016llx\n",
> start, start + size);
> return ERR_PTR(-EEXIST);
> }
>
> It assumes that MEMORY_HOTPLUG_RES_NAME will be a literal string, which
> is the case in [3/3].
@Andrew, as discussed in this thread already [1], I suggest to drop this
series from -mm tree for now.
[1] https://lkml.kernel.org/r/2e3419b2-d00c-51c3-9b45-9de114608cdf@xxxxxxx
--
Thanks,
David / dhildenb
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