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

[Pratik R. Sampat]

On 1/14/26 4:30 AM, David Hildenbrand (Red Hat) wrote:
> On 1/12/26 21:22, Pratik R. Sampat 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@xxxxxxx>
>> ---
>>   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>
>>     #include "internal.h"
>>   #include "shuffle.h"
>> @@ -1567,6 +1568,9 @@ int add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags)
>>       if (!strcmp(res->name, "System RAM"))
>>           firmware_map_add_hotplug(start, start + size, "System RAM");
>>   +    if (IS_ENABLED(CONFIG_UNACCEPTED_MEMORY))
>> +        arch_accept_memory(start, start + size);
>> +
>>       /* device_online() will take the lock when calling online_pages() */
>>       mem_hotplug_done();
>>   
> 
> As discussed, for things like virtio-mem or the HV-balloon this might be the wrong thing to do, but I don't expect these mechanisms to be used in CoCo environments just yet (and doing so would require enabling work for them).
> 

Ack.

> So I'm fine with this for now.
> 

Thanks!