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Mon, 22 Jun 2020 16:35:40 +0000 Subject: Re: [PATCH v2 00/11] KVM: Support guest MAXPHYADDR < host MAXPHYADDR To: Paolo Bonzini , Mohammed Gamal , kvm@vger.kernel.org Cc: linux-kernel@vger.kernel.org, vkuznets@redhat.com, sean.j.christopherson@intel.com, wanpengli@tencent.com, jmattson@google.com, joro@8bytes.org, babu.moger@amd.com References: <20200619153925.79106-1-mgamal@redhat.com> <5a52fd65-e1b2-ca87-e923-1d5ac167cfb9@amd.com> <08594d32-9be2-b4d6-1dac-a335e8bda9f7@redhat.com> From: Tom Lendacky Message-ID: <53dc2f58-1373-b0ef-9888-713712c6a85a@amd.com> Date: Mon, 22 Jun 2020 11:35:39 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 In-Reply-To: <08594d32-9be2-b4d6-1dac-a335e8bda9f7@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-ClientProxiedBy: DM5PR13CA0018.namprd13.prod.outlook.com (2603:10b6:3:23::28) To DM5PR12MB1355.namprd12.prod.outlook.com (2603:10b6:3:6e::7) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [10.236.30.118] (165.204.77.1) by DM5PR13CA0018.namprd13.prod.outlook.com (2603:10b6:3:23::28) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3131.10 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData: duoI6pCEkYYd3NsM60/dBDLrVDRJwCQbuRs7UZIQRdefV5463XP/hokQzdgUlJQU+RBKEfgfoPvxTPWavbxgZH9reJL/BT8AZNx7f2Hze7DAAIMsDsQf770sttxODpg2eBucecAe19owaioX6lrE0Gn3gQm4cUHt36YeDkDmklq7ZBTyPR8hgxqHvkNHicn9mch2mdKf4H4JMiFdqJox+e8qQMZrBjPD/3x9tlWrhk0F8mOa8sUISYzJiEr8KWqoSMnwv+ZVtl4DFN8x7VEuW/uWkd0MffWRAemiD/RaFOfjdaSiEpzOcvQrlxXD4sXjPDkVBdD4r/HV4lfSR2FXlghSVIfnG7/WblWQv2n4TbUchSKE2fQT9yHYzAsQtTgXRkGpAALF8ZX1Fjp3cBtCWAY+fA6CgeZGfnLq7hhKsmEaInEW7Qv8YdUgciTYPmBykS+anb76ZiuhCn7XprJG6AZUGo8SvUSZW/p/VqREHVA= X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-Network-Message-Id: 925f6d12-0dfa-435b-3c57-08d816ca4cf8 X-MS-Exchange-CrossTenant-OriginalArrivalTime: 22 Jun 2020 16:35:40.5056 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: DN6VbBOzHsqqOUqFgcecuAp4K3AzKfouFPKWSxzomhpw5XzODlBO/aADZHBiOnhIQmaOOrwCMmo2Qy1a7534QA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR12MB3370 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 6/22/20 10:23 AM, Paolo Bonzini wrote: > On 22/06/20 17:08, Mohammed Gamal wrote: >>> Also, something to consider. On AMD, when memory encryption is >>> enabled (via the SYS_CFG MSR), a guest can actually have a larger >>> MAXPHYADDR than the host. How do these patches all play into that? > > As long as the NPT page tables handle the guest MAXPHYADDR just fine, > there's no need to do anything. I think that's the case? Yes, it does. Thanks, Tom > > Paolo > >> Well the patches definitely don't address that case. It's assumed a >> guest VM's MAXPHYADDR <= host MAXPHYADDR, and hence we handle the case >> where a guests's physical address space is smaller and try to trap >> faults that may go unnoticed by the host. >> >> My question is in the case of guest MAXPHYADDR > host MAXPHYADDR, do we >> expect somehow that there might be guest physical addresses that >> contain what the host could see as reserved bits? And how'd the host >> handle that? >