linux-kernel - Re: [PATCH v2 1/2] mm/memory_hotplug: Add support to accept memory during hot-add

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Message-ID: <2f9b180b-c221-4631-93d0-c131332ef178@amd.com>
Date: Mon, 12 Jan 2026 16:23:37 -0600
From: "Pratik R. Sampat" <prsampat@....com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-mm@...ck.org, linux-coco@...ts.linux.dev, x86@...nel.org,
 linux-kernel@...r.kernel.org, tglx@...utronix.de, mingo@...hat.com,
 bp@...en8.de, dave.hansen@...ux.intel.com, kas@...nel.org, ardb@...nel.org,
 david@...nel.org, osalvador@...e.de, thomas.lendacky@....com,
 michael.roth@....com
Subject: Re: [PATCH v2 1/2] mm/memory_hotplug: Add support to accept memory
 during hot-add

On 1/12/26 3:04 PM, Andrew Morton wrote:
> On Mon, 12 Jan 2026 14:22:59 -0600 "Pratik R. Sampat" <prsampat@....com> wrote:
> 
>> Confidential computing guests require memory to be accepted before use.
>> The unaccepted memory bitmap maintained by firmware does not track
>> hotplugged memory ranges.
>>
>> Call arch_accept_memory() during the hot-add path to explicitly validate
>> and transition the newly added memory to a private state, making it
>> usable by the guest.
>>
>> Signed-off-by: Pratik R. Sampat <prsampat@....com>
>> ---
>>  mm/memory_hotplug.c | 4 ++++
>>  1 file changed, 4 insertions(+)
>>
>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
>> index a63ec679d861..8cfbf0541430 100644
>> --- a/mm/memory_hotplug.c
>> +++ b/mm/memory_hotplug.c
>> @@ -38,6 +38,7 @@
>>  #include <linux/node.h>
>>  
>>  #include <asm/tlbflush.h>
>> +#include <asm/unaccepted_memory.h>
> 
> This only exists for x86!

Ah, I missed that entirely. Thanks for catching that.

Probably not the best option to have a generic unaccepted_memory.h as well.
Maybe, I should have arch_[un]accept_memory() definitions within mm.h wrapped
within CONFIG_UNACCEPTED_MEMORY instead so that its cleaner.

> 
> Otherwise, the mm/ changes are minimal so I volunteer this patchset
> for the x86 tree ;)

Ack!

--Pratik