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Sat, 10 Oct 2026 06:41:34 +0000 Date: Sat, 10 Oct 2026 14:40:45 +0800 From: Yan Zhao To: "Edgecombe, Rick P" , "pbonzini@redhat.com" , "Hansen, Dave" , "seanjc@google.com" , "kvm@vger.kernel.org" , "Du, Fan" , "Li, Xiaoyao" , "Huang, Kai" , "thomas.lendacky@amd.com" , "tabba@google.com" , "vbabka@suse.cz" , "david@kernel.org" , "kas@kernel.org" , "michael.roth@amd.com" , "binbin.wu@linux.intel.com" , "linux-kernel@vger.kernel.org" , "Peng, Chao P" , "ackerleytng@google.com" , "nik.borisov@suse.com" , "francescolavra.fl@gmail.com" , "sagis@google.com" , "Annapurve, Vishal" , "Chen, Farrah" , "Gao, Chao" , "Miao, Jun" , "jgross@suse.com" , "pgonda@google.com" , "x86@kernel.org" Subject: Re: [PATCH v4 06/17] KVM: x86/mmu: Allocate DPAMT pages for vCPU-induced page split Message-ID: Reply-To: Yan Zhao References: <20260928090729.15468-1-yan.y.zhao@intel.com> <20260928091005.15567-1-yan.y.zhao@intel.com> <76157e3dcff065d444d83a9c5e7a924967fecc87.camel@intel.com> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: X-ClientProxiedBy: SI2PR04CA0008.apcprd04.prod.outlook.com (2603:1096:4:197::20) To DM6PR11MB3243.namprd11.prod.outlook.com (2603:10b6:5:e::19) 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: DM6PR11MB3243:EE_|DS7PR11MB6248:EE_ X-MS-Office365-Filtering-Correlation-Id: ff81aa03-77a6-46e6-1ab4-08df269986d0 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|23010399003|376014|1800799024|7416014|366016|6133799003|10067099003|18002099003|22082099003|261009223027099003|921020|11063799006|4143699003|5023799004|56012099006; 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The DPAMT cache is > > > currently a per-vCPU thread-local list. When a vCPU-induced page split > > > occurs, DPAMT pages can be drawn locklessly from the list. > > > > > > Pass min_nr_spts as 1 to .topup_external_cache(), indicating there's one > > > new S-EPT page table page. So, tdx_topup_external_pamt_cache() will > > > allocate DPAMT page pairs for both the newly added S-EPT page table page > > > and the demoted guest private page. > > > > > > tdp_mmu_alloc_sp_for_split() is currently not reachable from a non-vCPU > > > context for mirror roots, since dirty page tracking is not yet allowed on > > > mirror roots. So, simply add a WARN if tdx_topup_external_pamt_cache() is > > > invoked under a non-vCPU context. > > > > > > Signed-off-by: Sean Christopherson > > > Signed-off-by: Yan Zhao > > > --- > > > v4: new patch. > > > > New? It is essentially this with a new log, right? > > https://lore.kernel.org/kvm/20260129011517.3545883-39-seanjc@google.com/#t > Ha, "new patch" is relative to v3. > It's indeed introduced by Sean from the DPAMT combined v5. Let me add a Link to Sean's original post in the next version. > > Reviewed-by: Rick Edgecombe > > > > > >