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Sampat" Subject: Re: [PATCH v2 1/2] mm/memory_hotplug: Add support to accept memory during hot-add To: "David Hildenbrand (Red Hat)" , linux-mm@kvack.org, linux-coco@lists.linux.dev, x86@kernel.org, linux-kernel@vger.kernel.org Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, kas@kernel.org, ardb@kernel.org, akpm@linux-foundation.org, osalvador@suse.de, thomas.lendacky@amd.com, michael.roth@amd.com References: <20260112202300.43546-1-prsampat@amd.com> <20260112202300.43546-2-prsampat@amd.com> <4f2c6106-9cc1-4196-8b20-83b297ae7195@kernel.org> Content-Language: en-US In-Reply-To: <4f2c6106-9cc1-4196-8b20-83b297ae7195@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-ClientProxiedBy: SN7P220CA0016.NAMP220.PROD.OUTLOOK.COM (2603:10b6:806:123::21) To CH3PR12MB8660.namprd12.prod.outlook.com (2603:10b6:610:177::5) Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CH3PR12MB8660:EE_|DS0PR12MB6389:EE_ X-MS-Office365-Filtering-Correlation-Id: 63cd7925-131f-4f21-ab6e-08de53c033de X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|366016|376014|7416014; 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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 >> --- >>   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 >>     #include >> +#include >>     #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!