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Wed, 26 Feb 2025 02:09:10 +0000 Date: Wed, 26 Feb 2025 10:07:53 +0800 From: Yan Zhao To: Sean Christopherson CC: Rick P Edgecombe , "kvm@vger.kernel.org" , "pbonzini@redhat.com" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] KVM: selftests: Wait mprotect_ro_done before write to RO in mmu_stress_test Message-ID: Reply-To: Yan Zhao References: <20250208105318.16861-1-yan.y.zhao@intel.com> <23ea46d54e423b30fa71503a823c97213a864a98.camel@intel.com> <69a1443e73dc1c10a23cf0632a507c01eece9760.camel@intel.com> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: X-ClientProxiedBy: SGBP274CA0021.SGPP274.PROD.OUTLOOK.COM (2603:1096:4:b0::33) To DS7PR11MB5966.namprd11.prod.outlook.com (2603:10b6:8:71::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: DS7PR11MB5966:EE_|PH7PR11MB5885:EE_ X-MS-Office365-Filtering-Correlation-Id: c5b35eec-87a9-4b7a-4d7e-08dd560a8ec1 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|376014|1800799024; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?JkoK/FajejQyzvhCiSPh4qlaucG0GS0h9nO2ZxuKuNPy0+6txnHmEpaQOERH?= =?us-ascii?Q?dZO55iDiDAqkzzb0slEPAtssophH2yyLshMW9ISu70cLoi/E/JUbBqwZYB5C?= =?us-ascii?Q?seOtIp32mO4MAG1XJPzPE4R2hZ4U9RyMVoEsAulid3xe97Fvs4aferB+J8mz?= =?us-ascii?Q?RrkBm54qZLWCzCdsQyfY7fqgXJOS8/euXhQDDQ31fx7CSYSJCWFa0Xo8tKk8?= =?us-ascii?Q?kmlpRhIBEZbmqEfwOs5ZgsUcKO9lhurz+kjm3AbQqL0XoEYI2iopzTKkeM/w?= =?us-ascii?Q?rHjNi4YZV8fLVjyaN/pJd0bdmzN1nV4EZR6Tk8m/JodncxvCQuMX4IZfqqo/?= =?us-ascii?Q?wPnMMN0iiZguUfXrRljHXJzBoVuz8LT1o/SZpzsQaqV+TdfS90VIk04Cp3Uk?= =?us-ascii?Q?Hkc+U00zR5tHyglk8IN5QbK5x5wqz/YXoCh46QrmAYdCa6XAPy3Q6NraCh2+?= =?us-ascii?Q?h4mjXFJLOYWCv3VYJOFRA5Kan4mb165PR+Dpl3iyjIOJYSR2CnFgVaMQV0Hh?= =?us-ascii?Q?69YFQC0sPCsFjDPOLjI9VT4A/nd0tAbPxkpEv5be/Qd2At8rkPRsjaBEfGHu?= =?us-ascii?Q?BeDana4ASsgDgiHjNSfCq8ZXKEdidewghfa48rqztdDNlqv5o63OIVGMPu77?= =?us-ascii?Q?pFNi2IDuYr0E1Msg/IN4ao/HrksSZIoW9upktAkj9GRiqUT6CHGdzmgfJEKh?= =?us-ascii?Q?zrL0ODEoem21otp4kZG2xCiEvOMBc1iaStIJda5xbucvtqhlljFy8Wf5TYXp?= =?us-ascii?Q?wuHh0ZnVO+zyhr3r8txPw4d1fMJwK4G2+AzigzBPl+5TkE4kIhjrevXmOuf9?= =?us-ascii?Q?k1jOPNCbiw5NmaT7KSHVC0BUANvx4BLR1ReMQJ1D0xduWMhwvOTK2p/iCA9L?= =?us-ascii?Q?Z2wloln1jppayXPptrnXDHxHNGGUjOOS4iZ8EVPx2yOfvkB7spW3cXMPWBmD?= =?us-ascii?Q?WGr0XO1RPO4a4KusGjuO+fO5YIRe4Enkits33RaQybcvfMUEWVClEYWTUOlv?= =?us-ascii?Q?N9O2PVcM7he9bFCEhS+SBe0WsSVtuIG1HrhR5jzFz4kkBcy4odk+l8CJbzD6?= =?us-ascii?Q?GUv2eEQjg83DV3Mfrfi+nH5X8C0N8GQFcDjUPnW18B95mMvX6RWdGrjG4DNu?= =?us-ascii?Q?MnZ9XxqaGyvlL67426aB8EQWZj+y1Zdwc30pFXl1Sde2waFi/uwVTeoW6Ira?= =?us-ascii?Q?qRf8NoK5F/kyc2qIcGo2J0XtQmQlRGRkbuv0s3rqWGR0qAqmkAdEDdWCmfxK?= =?us-ascii?Q?tBy46XRN4g5o1pblbipdO8BzUjmHAQvLfFGGfWXK5PgVMZqz+m5rjyF1jJv6?= =?us-ascii?Q?Ze/bTdtyThl6435CUS5T/l7WU50nyVaDm0R2gvwG9IJCwFsQ3KRmxZ+VhqNS?= =?us-ascii?Q?26T1UWYYE/2JJ+eta8Rrbv+26tkDdolfqwjOXxFfAYwviXB+mJcWXcPtRlk9?= =?us-ascii?Q?4iUkdTPpxcI02UTmh229hgi7Y0+1mu4MAvnyq+jgTDJrWq5+VXrWIwx/GZow?= =?us-ascii?Q?/OhUGUxKV/qDexb7Rbqt5iIQ7trGEFKqZJqn1+daFG29GU6lRzi0wDWiWKq8?= =?us-ascii?Q?szrOeLy4z/blNLECo+aszpFNJWG7M15bFHdmmmUC?= X-MS-Exchange-CrossTenant-Network-Message-Id: c5b35eec-87a9-4b7a-4d7e-08dd560a8ec1 X-MS-Exchange-CrossTenant-AuthSource: DS7PR11MB5966.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 26 Feb 2025 02:09:10.3401 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: 0bVpsfPdF2LgLzKtrEy0Gr47hG8QJfoFoCsQ68TdRpybzJ8Ie70GSDRRLV0oCVPlulMjaPKsPVUeLCCOq5RKhQ== X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH7PR11MB5885 X-OriginatorOrg: intel.com On Tue, Feb 25, 2025 at 05:53:49PM -0800, Sean Christopherson wrote: > On Tue, Feb 11, 2025, Rick P Edgecombe wrote: > > On Tue, 2025-02-11 at 09:42 +0800, Yan Zhao wrote: > > > > On the fix though, doesn't this remove the coverage of writing to a > > > > region that is in the process of being made RO? I'm thinking about > > > > warnings, etc that may trigger intermittently based on bugs with a race > > > > component. I don't know if we could fix the test and still leave the > > > > write while the "mprotect(PROT_READ) is underway". It seems to be > > > > deliberate. > > > Write before "mprotect(PROT_READ)" has been tested in stage 0. > > > Not sure it's deliberate to test write in the process of being made RO. > > Writing while VMAs are being made RO is 100% intended. The goal is to stress > KVM's interactions with the mmu_notifier, and to verify KVM delivers -EFAULT to > userspace. > > Something isn't quite right in the original analysis. We need to drill down on > that before change anything. > > FWIW, I run this test frequently on large systems and have never observed failures. Could you try adding CONFIG_LOCK_STAT=y? With this config, the failure rate is more than 90% in my SPR non-TDX machine, and 20%~80% in my TDX machine. > Maybe Rick and I should go buy lottery tickets?