Subject: Re: [FIX PATCH v0] powerpc: Fix memory unplug failure on radix guest

From: "Aneesh Kumar K.V" <[email-masked]>
Date: Fri, 11 Aug 2017 14:07:51 +0530

Reza Arbab <[email-masked]> writes:

> On Thu, Aug 10, 2017 at 02:53:48PM +0530, Bharata B Rao wrote:
>>diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
>>index f830562..24ecf53 100644
>>--- a/arch/powerpc/kernel/prom.c
>>+++ b/arch/powerpc/kernel/prom.c
>>@@ -524,6 +524,7 @@ static int __init early_init_dt_scan_drconf_memory(unsigned long node)
>> 					size = 0x80000000ul - base;
>> 			}
>> 			memblock_add(base, size);
>>+			memblock_mark_hotplug(base, size);
>> 		} while (--rngs);
>> 	}
>> 	memblock_dump_all();
>
> Doing this has the effect of putting all the affected memory into 
> ZONE_MOVABLE. See find_zone_movable_pfns_for_nodes(). This means no 
> kernel allocations can occur there. Is that okay?
>

So the thinking here is any memory identified via ibm,dynamic-memory can
be hot removed later. Hence the need to add them lmb size, because our
hotplug framework remove them in lmb size. If we want to support
hotunplug, then we will have to make sure kernel allocation doesn't
happen in that region right ?

With the above i would consider not marking it hotplug was a bug before
?

-aneesh