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Peter Anvin" , Tony Luck , Dave Hansen , "Peter Zijlstra (Intel)" , Paolo Bonzini , Tom Lendacky , David Rientjes , Sean Christopherson Subject: Re: [RFC Part1 PATCH 13/13] x86/kernel: add support to validate memory when changing C-bit To: Borislav Petkov References: <20210324164424.28124-1-brijesh.singh@amd.com> <20210324164424.28124-14-brijesh.singh@amd.com> <20210412114901.GB24283@zn.tnic> <20210412130542.GD24283@zn.tnic> From: Brijesh Singh Message-ID: Date: Mon, 12 Apr 2021 09:31:41 -0500 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.9.0 In-Reply-To: <20210412130542.GD24283@zn.tnic> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US X-Originating-IP: [70.112.153.56] X-ClientProxiedBy: SA0PR11CA0003.namprd11.prod.outlook.com (2603:10b6:806:d3::8) To SN6PR12MB2718.namprd12.prod.outlook.com (2603:10b6:805:6f::22) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from Brijeshs-MacBook-Pro.local (70.112.153.56) by SA0PR11CA0003.namprd11.prod.outlook.com (2603:10b6:806:d3::8) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4020.17 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData: =?utf-8?B?U0lkTUdMOWJaL0NhQlhUaUNVTW5QNmVlQ05qTDNhU0QzZm4xTko3U1pYSjNi?= =?utf-8?B?QkRZOWova2RGWGVZd2hudDNyWnJ0R0N1SHZUMGdwc01SOGdZcGZDR0pEQkE4?= =?utf-8?B?d05HVGpxWTJVR2x3WHJvMU9PVUNWTmgrLzYwZkhvczIrSXBGMGZBeFMvRnhn?= =?utf-8?B?VEgyV3JjRFdlb1JuZi94Y0I3MmlsWjcxSkJya1R6K0hUMzU5cnNHb0s3aHZy?= =?utf-8?B?WVVINmNveFVrckFYdW01YkY1SGN4NHAwUEZEeC9Wc0krTFBXOEpuVlozOUtQ?= =?utf-8?B?SFVhTWJaMFphYzZpMHI5SFk4bVYvakp0V0VJTVFBdFFlM0RGdnp3WWZqWmQ2?= =?utf-8?B?aFlTY00zRlVkTmVYbmEwM1RoNjVwNzI2eDBpeS9zMjR4eWlvd0VVWlVsVXdJ?= =?utf-8?B?T1ZHdTYvS2N0encyMVpscHlNS0FYVkRJWXZwV1Bzdmd4Sk9Vei9ObGFJWGl2?= =?utf-8?B?VXF5dFgxNmgxbFZsdEJaNXAxSk9vR3ZYWm91WTNSQTBvZmdyR3FUb2o5QVVB?= =?utf-8?B?UDRnbGJMSlNGZ2NTTFgyRkgyWFRIMjJ6MUk1cVpscmNuZERJZExQMTdoK1J6?= =?utf-8?B?THpDMXlpTVY0Rlh1UlRuNVUxVURQSitJVlVJN1dSZXBxTkttb0wwTXdkSnBa?= =?utf-8?B?QnIzbjQzVTc3LzJPQlRrUDArZkFIV0tuY052TG9jUUxBUEV3THlLbmlaRU5Z?= =?utf-8?B?Qk9qVG1naHlDQ0h0Z0NnT3BnMEI0ZjBiYVZxNUdFSFFPczVsYVlKMWdiUWtu?= =?utf-8?B?TUMwQ1RVa0FpOXpudnJHZWJIbElFQWcrU1h4ZlUvc1h1dmd4bE9EdjkxNWRH?= =?utf-8?B?S1NLMWZ5aGRwZ0lHajlMSTdqTGxHeXVoT3dRZHh2RTNHdjhTcTVkaElKMHIw?= =?utf-8?B?aCtiaWxlb3ZKRmo3cG9TWXlucS9laFlSVjZhSXVtd1VRbDlyUlA3cDdGWjl4?= =?utf-8?B?UjB1Qk44UmgxaGkwU1Vxb2d2RzFzemR0N0lwNDBST0x0bGQyMldWVE5ZTnk5?= =?utf-8?B?dko2MlhhT2I4NFJwaGFHeFFINXErTmc5SVA4RnhuNnV6M21aTE91eXloTEVM?= =?utf-8?B?WjJVdm10NTRmeTM2YUE5MXVCU0lDT3ZMRU5haGRDWExwZTJGcVpBTGJXUisx?= =?utf-8?B?MnNtRkVLNW1lc1hMWUZZUElTQ3ZNSnVydDl4NjM3Q2xjUDhZR2I0dDhPUFlU?= =?utf-8?B?SjVRTHlMcDF3dTFwd2xCZ0FNLzNwd3BGU0txaW16UmxMMVVFakdhbndLazBY?= =?utf-8?B?WTNua0tQVExldXFHYVpiQzVRdTRRU3F2NlRydDFtZmJFemp3d0kyYzdhaEZS?= =?utf-8?B?a2RISGZtYjdPbFdWQ3FjdndJdEV6K0VXUnlGNkxlVnJXcmd2WEdOMHFGOGY5?= =?utf-8?B?VzdNMFBoSHptVnB2djQvQU5SakRhUEtpMDBBNGFzZXNQaG5nWHJrQUZidXpl?= =?utf-8?B?d2o2b00wODJYbFU4anVjKzFJQVE0V0hDbmpSdTRxZjV4bE9jaVdzTnBiNzBP?= =?utf-8?B?WVV6STcxRG1xUlFPUnBMMTdZMGY0OE5sdklCQmVmSGhiWDVWVms5UmtwS1h6?= =?utf-8?B?TnFNNFYra3VORTNnTDNVcUVMdVJSaXV6STVVNWFJQlk1c2Eyb1pldWNsVnFl?= =?utf-8?B?dDVEdFZxQWwzMCtsdWd4OWRVSk9QZ0oyQTVYZDVTWVB2NmtoUWhzZXV0aVp4?= =?utf-8?B?aFFpVkdPY1BIYVBYY3ZmTlRrenQxekdaQkZoRXRUT2hEQnI5ZGcvWFdFelo2?= =?utf-8?Q?cMoPGwvxHRzwJuIQM4Xh4ZYgKqC19dkayTBOACB?= X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-Network-Message-Id: 9dfbe096-33ec-4b79-046b-08d8fdbfb1e5 X-MS-Exchange-CrossTenant-AuthSource: SN6PR12MB2718.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 12 Apr 2021 14:31:44.2839 (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: xB83CDXffdCVHgVEA0yB0rTpgbqk25cN3I0GGylggESVLXOG1GBdNNWaCoO8jY6jpfj5wQBHDVoCLPjlHUCSYA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA0PR12MB4573 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/12/21 8:05 AM, Borislav Petkov wrote: > On Mon, Apr 12, 2021 at 07:55:01AM -0500, Brijesh Singh wrote: >> The cur_entry is updated by the hypervisor. While building the psc >> buffer the guest sets the cur_entry=0 and the end_entry point to the >> last valid entry. The cur_entry is incremented by the hypervisor after >> it successfully processes one 4K page. As per the spec, the hypervisor >> could get interrupted in middle of the page state change and cur_entry >> allows the guest to resume the page state change from the point where it >> was interrupted. > This is non-obvious and belongs in a comment above it. Otherwise it > looks weird. Sure, I will add the comment and provide reference to the GHCB section. Thanks