Re: [PATCH] mm/hotplug: Only respect mem= parameter during boot stage

David Hildenbrand
2019-12-09T09:43:25Z

On 06.12.19 16:05, Baoquan He wrote:
> In commit 357b4da50a62 ("x86: respect memory size limiting via mem=
> parameter") a global varialbe global max_mem_size is added to store
> the value which is parsed from 'mem= '. This truly stops those
> DIMM from being added into system memory during boot.
>
> However, it also limits the later memory hotplug functionality. Any
> memory board can't be hot added any more if its region is beyond the
> max_mem_size. System will print error like below:
>
> [ 216.387164] acpi PNP0C80:02: add_memory failed
> [ 216.389301] acpi PNP0C80:02: acpi_memory_enable_device() error
> [ 216.392187] acpi PNP0C80:02: Enumeration failure
>
> From document of 'mem =' parameter, it should be a restriction during
> boot, but not impact the system memory adding/removing after booting.
>
> mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
>
> So fix it by also checking if it's during SYSTEM_BOOTING stage when
> restrict memory adding. Otherwise, skip the restriction.
>
> Fixes: 357b4da50a62 ("x86: respect memory size limiting via mem= parameter")
> Signed-off-by: Baoquan He <bhe@redhat.com>
> ---
> mm/memory_hotplug.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 55ac23ef11c1..5466a0a00901 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -105,7 +105,7 @@ static struct resource *register_memory_resource(u64 start, u64 size)
> unsigned long flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
> char *resource_name = "System RAM";
>
> - if (start + size > max_mem_size)
> + if (start + size > max_mem_size && system_state == SYSTEM_BOOTING)
> return ERR_PTR(-E2BIG);
>
> /*
>

Sounds sane to me.

Acked-by: David Hildenbrand <david@redhat.com>

--
Thanks,

David / dhildenb