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Mon, 28 Apr 2025 22:48:50 +0000 Date: Mon, 28 Apr 2025 15:48:45 -0700 From: Dan Williams To: Dave Hansen , Dan Williams , CC: Kirill Shutemov , Vishal Annapurve , Kees Cook , , , Nikolay Borisov , Naveen N Rao , Ingo Molnar , , , Arnd Bergmann , "Greg Kroah-Hartman" , , Subject: Re: [PATCH v3 0/2] Restrict devmem for confidential VMs Message-ID: <681005cdd3631_1d522948e@dwillia2-xfh.jf.intel.com.notmuch> References: <174491711228.1395340.3647010925173796093.stgit@dwillia2-xfh.jf.intel.com> <63bb3383-de43-4638-b229-28c33c1582be@intel.com> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <63bb3383-de43-4638-b229-28c33c1582be@intel.com> X-ClientProxiedBy: MW4PR03CA0316.namprd03.prod.outlook.com (2603:10b6:303:dd::21) To PH8PR11MB8107.namprd11.prod.outlook.com (2603:10b6:510:256::6) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: PH8PR11MB8107:EE_|PH8PR11MB7000:EE_ X-MS-Office365-Filtering-Correlation-Id: 3f516e73-e5d2-4dee-7275-08dd86a6d7aa X-LD-Processed: 46c98d88-e344-4ed4-8496-4ed7712e255d,ExtAddr X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|376014|7416014|366016; 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We can take it through > tip, but one things that makes me nervous is that neither of the "CHAR > and MISC DRIVERS" supporters are even on cc. > > > Arnd Bergmann (supporter:CHAR and MISC DRIVERS) > > Greg Kroah-Hartman (supporter:CHAR and MISC DRIVERS) Good catch, just note that until this latest iteration the proposal was entirely contained to x86 specific support functions like devmem_is_allowed(). So yes, an oversight as this moved to a more general devmem mechanism. > I guess arm and powerpc have cc_platform_has() so it's not _completely_ > x86 only, either. Acks from those folks would also be appreciated since > it's going to affect them most immediately. I have added Suzuki and Michael for their awareness, but I would not say acks are needed at this point since to date CC_ATTR_GUEST_MEM_ENCRYPT is strictly an x86-ism. For example, the PowerPC implementation of cc_platform_has() has not been touched since Tom added it. Suzuki, Michael, at a minimum the question this patch poses to ARM64 and PowerPC is whether they are going to allow CONFIG_STRICT_DEVMEM=n, or otherwise understand that CONFIG_STRICT_DEVMEM=y == LOCKDOWN with CC_ATTR_GUEST_MEM_ENCRYPT. > Also, just to confirm, patch 2 can go to stable@ without _any_ > dependency on patch 1, right? Correct. I will make them independent / unordered patches on the repost. Next posting to fix the "select" instead of "depends on" dependency management, h/t Naveen, and clarify the "'crash' vs 'SEPT violation'" description.