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client-ip=165.204.84.17; helo=satlexmb08.amd.com; pr=C Received: from satlexmb08.amd.com (165.204.84.17) by SJ1PEPF00002319.mail.protection.outlook.com (10.167.242.229) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9520.1 via Frontend Transport; Tue, 13 Jan 2026 22:35:05 +0000 Received: from Satlexmb09.amd.com (10.181.42.218) by satlexmb08.amd.com (10.181.42.217) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.17; Tue, 13 Jan 2026 16:35:03 -0600 Received: from [10.236.181.95] (10.180.168.240) by satlexmb09.amd.com (10.181.42.218) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.17; Tue, 13 Jan 2026 14:35:02 -0800 Message-ID: <988ca415-ea91-4509-8552-5b8829d9e8f0@amd.com> Date: Tue, 13 Jan 2026 16:35:02 -0600 Precedence: bulk X-Mailing-List: linux-cxl@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 6/6] cxl/sysram: disallow onlining in ZONE_NORMAL if state is movable only To: Gregory Price CC: , , , , , , , , , , David Hildenbrand , "Hannes Reinecke" References: <20260112163514.2551809-1-gourry@gourry.net> <20260112163514.2551809-7-gourry@gourry.net> <9c975c63-2668-4283-a326-292e50bfbfec@amd.com> Content-Language: en-US From: "Cheatham, Benjamin" In-Reply-To: Content-Type: text/plain; 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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 13 Jan 2026 22:35:05.5898 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: b7d3502e-e941-4f78-1372-08de52f3ffea X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[satlexmb08.amd.com] X-MS-Exchange-CrossTenant-AuthSource: SJ1PEPF00002319.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: LV8PR12MB9153 On 1/12/2026 5:14 PM, Gregory Price wrote: > On Mon, Jan 12, 2026 at 03:11:05PM -0600, Cheatham, Benjamin wrote: >> On 1/12/2026 10:35 AM, Gregory Price wrote: >>> If state is set to online (default to ZONE_MOVABLE), the user intends >>> for this memory to either refuse non-movable allocations, and/or intends >>> to preserve the hot-unpluggability of this memory. However, any admin >>> can write `offline` and `online` to the memory block controller and >>> bring that memory online in ZONE_NORMAL. >> >> Is it the expectation that the user will never want to change the zone from >> MOVABLE to NORMAL? I can't think of a reason someone would want to off the top >> of my head, but I also can't think of a reason to restrict it either. >> > > It's more to restrict this pattern > > echo online_movable > region0/hotplug > -> creates: node1/memory123/ > > echo offline > node1/memory123/state > echo online > node1/memory123/state > > The result of this would be valid_zones=[normal movable], which would > break hot-unplug. Ahh ok I think I get it now. I wasn't thinking about bypassing the memctrl/ interface and using the memory block sysfs directly. Thanks for the explanation! Thanks, Ben > >>> If an actor attempts to online the block into ZONE_NORMAL, it will fail, >>> but if it attempts to online into either NORMAL or MOVABLE, only MOVABLE >>> will be allowed and it will succeed. >> >> I'm not sure you need this paragraph. I think it's a logical conclusion of the above >> that if someone attempts to online the memory as NORMAL or MOVABLE it'll only be onlined >> as MOVABLE. > > in the above situation the following occurs: > > echo online > region0/hotplug > echo offline > node1/memory123/state > echo online > node1/memory123/state > cat node1/memory123/valid_zones > normal movable > echo offline > node1/memory123/state > echo 1 > node1/memory123/online > cat node1/memory123/valid_zones > normal > > > echo online_movable > region0/hotplug > echo offline > node1/memory123/state > echo online > node1/memory123/state > cat node1/memory123/valid_zones > movable > echo offline > node1/memory123/state > echo 1 > node1/memory123/online > fail with EXXXX (i forget what code) > > It's a little confusing. > >>> + switch (data->last_online_type) { >>> + case MMOP_ONLINE_MOVABLE: >>> + return sysfs_emit(buf, "online\n"); >>> + case MMOP_ONLINE_KERNEL: >>> + return sysfs_emit(buf, "online_normal\n"); >>> + case MMOP_OFFLINE: >>> + default: >> >> You're missing the MMOP_ONLINE case. In that case the memory would be reported as "offline", which >> I doubt is the intention. >> > > Blah, i originally had all of them and just reduced to > MMOP_ONLINE_MOVABLE and MMOP_ONLINE (i don't see a good use for > MMOP_ONLINE_KERNEL), but i'll fix this up. > > Thanks! > Gregory