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Peter Anvin" , Ard Biesheuvel , Paolo Bonzini , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Andy Lutomirski , Dave Hansen , Sergio Lopez , Peter Gonda , Peter Zijlstra , Srinivas Pandruvada , David Rientjes , Dov Murik , Tobin Feldman-Fitzthum , Borislav Petkov , Michael Roth , Vlastimil Babka , tony.luck@intel.com, npmccallum@redhat.com, brijesh.ksingh@gmail.com Subject: Re: [PATCH Part2 RFC v4 10/40] x86/fault: Add support to handle the RMP fault for user address To: Dave Hansen , x86@kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-efi@vger.kernel.org, platform-driver-x86@vger.kernel.org, linux-coco@lists.linux.dev, linux-mm@kvack.org, linux-crypto@vger.kernel.org References: <20210707183616.5620-1-brijesh.singh@amd.com> <20210707183616.5620-11-brijesh.singh@amd.com> <3c6b6fc4-05b2-8d18-2eb8-1bd1a965c632@intel.com> <2b4accb6-b68e-02d3-6fed-975f90558099@amd.com> <5592d8ff-e2c3-6474-4a10-96abe1962d6f@amd.com> From: Brijesh Singh Message-ID: Date: Mon, 12 Jul 2021 11:24:16 -0500 User-Agent: Mozilla/5.0 (X11; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?SG9GMExmSk9MZ0lyZkNnaCtYdHoxV0xnSlltSEtwY3BDazNxMEwvbjIwVmd3?= =?utf-8?B?dGV1UEZwd3FxYlpDY0RaWVV4QWpJdTBkZFIrWTZoT2lBdXkwV090SjczQ2Mw?= =?utf-8?B?TmcreGc1a0t1SUFQOFBSUWttOFBveUJCaW53YXVrdEVBNVpEVlc5VktISTN2?= =?utf-8?B?eTFxdldZM0xnc0Y0ODVzNVplSVZSdm1hc3IyM2ZQWndYSEQ4elhZdWxKWVAz?= =?utf-8?B?MHB2QjU4Y08wSjd5M0krUVYrejVWKzFDSTM1c2FKbUFudmtoR2R3NjJ0SFhw?= =?utf-8?B?U3FsNFRuak1kOHpzS3A3Q1NSMWV2eE9vVjI1RkZNS2graEZ0TnVxQWt4eW9O?= =?utf-8?B?WHZveTFrMXhkOCtKWGR6eUNtMDRsOHVFRmtseG1jS2IycDhYVzdHMVZUNXJk?= =?utf-8?B?LzVsZjBmbjRHNzhtcTFUR3gxRnRvTHB0Q1p4dFpZTXlkOGhURmJuSDlDemNz?= =?utf-8?B?VkFtbytVMlRHSnBGbUhqYWwwSXJSNERQczZvdCtwdGc0QStUWWo1aTJTdkxH?= =?utf-8?B?R2pqQVN4KzdhMWRuN2tqUU4wY0lwaTBVSjF6SkhmTDhEM0ZkSld4Um1uM2M1?= =?utf-8?B?bUtWTDJ0SDQzajA2MW5taC9lSHRVRjdWZWtXNVpFa3BRdmJ2aCtYWTR3S2pE?= =?utf-8?B?N25raS9CRzZielQ5V3ltcGZNM2FUY0U2eU9ZTTlIL2l3YVJnVXZLWUJQYnhx?= =?utf-8?B?cnUyZ1MrTHN2bU55eFg4SFdZYXFLeHY0TTYzSGFHTUdGT284bURXaXVyT01z?= =?utf-8?B?UDNEU3BBUitCRmUxUlppVXR0RnlLZ3IvT1g3ejczZ0g2djdLcUY5VU16a2F6?= =?utf-8?B?Z1VFcDRna1dJWEhsMlNRZW84ZEh0dFNFc3ZMK3Y4WjlYejdrUWkvTlRGeE4y?= =?utf-8?B?VzZyNWo3ZXZKZWhvUXJZam5qa3dtNGI3cXJZMk1BdHRPT1d1Vm9hRGdNcG9z?= =?utf-8?B?UTRoZm92enJ5cXBaeTRrM2xhMU9ZY3FzYXd6WTcrUEZSN1pDbDRkUGhCclBM?= =?utf-8?B?eDIyMTlJYk1UcGg1M2djQm9VM3ROWi9ncnhrUytTdzRWeTBPV0QzSUhSODRG?= =?utf-8?B?VnpoWHVZNkliREowNnV3SXdvb3p0WnpBZ0pUSEpwQUkrRWtQRWpZV1R0aUJs?= =?utf-8?B?bnkxaUNxQW1GQ3dQaFgvRW5sWlZYVEtRWjFlenR2ZXNNSkwvbjA3aWJwYWlQ?= =?utf-8?B?M20xVGFtR0ZhYTFSSWJ6L29DU3hHZFk3NzJ4SDJ2YjFDMHR4LzVybUJQT05K?= =?utf-8?B?dWtFTjNCZDZ3SXJRMmYyUTdHTFNCeWpmRnNTNUJxNk5FNDgzQm9GbGo0OXEw?= =?utf-8?B?SHQvcGUvN0UxQk55NjZSYk5WbDhzcGJjQUlPRFJQUmx4Q2JLaHRSaENwNVA1?= =?utf-8?B?SkNZbmZuRSt3Y3pmMDIyZ0lJdFVRVyt6dDN3ZlBwZzFBTXJ5ck96dC9uTE1S?= =?utf-8?B?Y1ZyU0Rjd3gwRTdQWVc4bjFKWTVyWldmQjBIV0RBU2RaNi9IL3E4NTJZU29K?= =?utf-8?B?bmVWV2V0ejZ0L0h3TGk3NUxZNnJ1NUhZLzFRbXZZMjFKMUZ4QXZnRG4vRUpT?= =?utf-8?B?U1M3YWdEMVNSTkE4SHpkcHZUNFpQbDhESHRUTDlvTnQ4eUgxU0JSTzRiMWs0?= =?utf-8?B?dGQ2MnpqRDE2SEpkcmttRWd6WTdsUjFVbFV1dDl6UmJZVUdDMXY1UGpGSkpV?= =?utf-8?B?WmF5T3lRN1hCWWlFMVRUUVVuc25zckY3dkU4VGlzYUFsV090R0F5Z2FXMkhr?= =?utf-8?Q?/b6g1p4qMv1ZSADmmqTzSvxwSlAHI65KFJbKrMf?= X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-Network-Message-Id: 3e28969f-b22f-4db6-9e64-08d945517f85 X-MS-Exchange-CrossTenant-AuthSource: SN6PR12MB2718.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 12 Jul 2021 16:24:18.5765 (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: elNt02YnVp/4cXbzBUg0BtC4M6D4DK2xzAV2Pf1m5DOI2rwvyPzcSc6E1cDmB2+G+pveBXgISx2PcRNTr35Bjw== X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA0PR12MB4431 On 7/12/21 11:15 AM, Dave Hansen wrote: > On 7/12/21 9:11 AM, Brijesh Singh wrote: >>> Please fix this code to handle hugetlbfs along with any other non-THP >>> source of level>0 mappings.  DAX comes to mind.  "Handle" can mean >>> rejecting these.  You don't have to find some way to split them and make >>> the VM work, just fail safely, ideally as early as possible. >>> >>> To me, this is a fundamental requirement before this code can be >>> accepted. >> >> Understood, if userspace decided to use the hugetlbfs backing pages then >> I believe earliest we can detect is when we go about adding the pages in >> the RMP table. I'll add a check, and fail the page state change. > > Really? You had to feed the RMP entries from *some* mapping in the > first place. Is there a reason the originating mapping can't be checked > at that point instead of waiting for the fault? > Apologies if I was not clear in the messaging, that's exactly what I mean that we don't feed RMP entries during the page state change. The sequence of the operation is: 1. Guest issues a VMGEXIT (page state change) to add a page in the RMP 2. Hyperivosr adds the page in the RMP table. The check will be inside the hypervisor (#2), to query the backing page type, if the backing page is from the hugetlbfs, then don't add the page in the RMP, and fail the page state change VMGEXIT. -Brijesh