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Wed, 2 Apr 2025 01:10:59 +0000 Date: Wed, 2 Apr 2025 09:09:22 +0800 From: Yan Zhao To: Sean Christopherson CC: Paolo Bonzini , , Subject: Re: [PATCH] KVM: VMX: Add a quirk to (not) honor guest PAT on CPUs that support self-snoop Message-ID: Reply-To: Yan Zhao References: <20250401221107.921677-1-seanjc@google.com> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: X-ClientProxiedBy: KL1PR0401CA0023.apcprd04.prod.outlook.com (2603:1096:820:e::10) 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_|DS0PR11MB8739:EE_ X-MS-Office365-Filtering-Correlation-Id: 21147dcd-d567-4373-29bc-08dd71833abe X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|366016|376014|7053199007; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?flsxwf+YqBeCPZBb0hedayBX/Dtog7+cYaZff2BlQC0iYPlqX+hDoIcy3/ms?= =?us-ascii?Q?WK+jPaXJNumgOAFiDS0mSCSXhF3ysN6HlduBr0kb1oVcKdPF1WXPDdvSJOii?= =?us-ascii?Q?nVsbQmW0D65DEAMSw0m/vios+4WLGqGcRrCpUV3hWSojWo+nsDU2k6eqCt0y?= =?us-ascii?Q?QK985C7d8d8GN2AdDX0J0KdnvYSng3EaIzS6K2YtPSkUcRsHR0EkEXhvxxrS?= =?us-ascii?Q?RADaWWxJ5cv5iGxAif1eEQGJ/5ErfDKaRtsmpNAcRnvcrvfbVqc0GpAMDp5Q?= =?us-ascii?Q?4fpD2o8hIVRIO9SK9htZ4xBT+9PL+4uc1T3gokHBEzvmPZTNJQunlHYD9AqN?= =?us-ascii?Q?IWJ7nNU08RrJTg59hrDSl6afSM3GnwbNmF+aDmUle2E8HUuw9/pdpWeHipxq?= =?us-ascii?Q?RTmUrWtzh8G6jmdbmvib8sOyEdpRd4hQk/Ob6N0TqjhMuvQ4XFWzQz21rjv8?= =?us-ascii?Q?yXYXyuvwSZTxAiIgqQbTRa96H/BVBQo2p5GG3w/q/gok73wg9LhtqkCSvoml?= =?us-ascii?Q?kBo3cKBFZapSLMwMKcyOObLESs2fExTNyM8gLJk0R7TV277Y+ueXwquMAHA5?= =?us-ascii?Q?8VuHKdgWkcL6CpsmIcfpMowmpxvDb9HDZgChVFbZa/zLCmcbYH3IfR8ZaCWR?= =?us-ascii?Q?K6Ymhdtwws6al+P0RWocM07SPwnrH5DGZdbOUT0e3C2cRHxobMamJpQ0QZ4G?= =?us-ascii?Q?qGuyGehS5P5JSjypzwu1i6ZO/lggusrNz02ihP+s17uLIsZZfF4r9caqzzUQ?= =?us-ascii?Q?FsT0Vw1sfVaqpl3JxKj9lnN9swYEBFzaa5WeNtb+z9dcWphz+oVL+eQZrN8u?= =?us-ascii?Q?Oi3i8i4iwzXDmdichPlGloKO+iqR7xlVoBtP6/KUdAKNDwplKQyDl+6wLtsF?= =?us-ascii?Q?jV7hLV71C/73Yo4Po96VDJ5ERKo9LL23w0jBRVGCL7jEMRVEjuxnpVDdAdSX?= =?us-ascii?Q?EklSCOwGp8GdDJWowXWv2b8uBL8x/zCy1jJB0GWLcNihVGA4AG3Q2xpOWNh5?= =?us-ascii?Q?3PJXYUSzOmuVfC4jjrawGIRJ6W0AyROrptzdyKNzWC2J+tyJKMYJ7S7WSOO/?= =?us-ascii?Q?VhMmCGWYha+2tlg75LuWCRBPOiamOxFRTJ5HSqsP7sbXlrD5eVOP4cjTWakQ?= =?us-ascii?Q?6b2TPOmobPl40038vdg3jD6phgGfFjP/YbuW8bwxQNjQeWdNr3Hb8rizaQtS?= =?us-ascii?Q?tCVY9UUgSh+GgmD5x+x9Ciq/TlyUaS2Oa+2s9E7bYT2/LBSeGJMFLUgQPgi+?= =?us-ascii?Q?jVBYvWBkaoTLXeaaT8NUebSqAI0D3tMh0L2bcLi5SDrjJohEpDf9dBqbr/RP?= =?us-ascii?Q?i9cQ2xjwBzlPp8rd90aNgGQCtno4pjKandAJujaU0SSF09Xke4sWzIjQ5WL3?= =?us-ascii?Q?G6bFud2ndITNOQ7sopKraUsAHW6c?= X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:DS7PR11MB5966.namprd11.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(1800799024)(366016)(376014)(7053199007);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?k0uIniG1EZY6+03YkaH0coiyBBAyNmt4VBOFmyUCUBEZh8qZp2ENYmLs8Y8d?= =?us-ascii?Q?6++hPmx4HjHoUB45AeluqJ2UzI5RGjPo7N6xEZmId4L98DEP49rvyiId8Gvh?= =?us-ascii?Q?ryBy9ilgYlNpnXR7n4uZGQ6umg7T/whtauhJCn8uey3TYycNdIpp0gA6h18V?= =?us-ascii?Q?9uBOEZEul4tD7z9Cv/i180COLnYUKjDc6OAgua9UsQiYN7o/6w8jxJ3SAJ3Q?= =?us-ascii?Q?shaS4miqirs4vhWRZjZ6N6vR3HqxaxT6CLaQF320uwNuxgvWWvdqK4F51Zxu?= =?us-ascii?Q?g4YmIQoe/qLwwKNTwIZ5h6SqWpf5mHUVMFYUwpRVcggtw4YAYsvWQb1OYNCW?= =?us-ascii?Q?m758nHYX8eAwGu+Gsz3/OrtKPvnaQOBJJrzN0YzS5ed1WI/op3BoC1+Jgg4P?= =?us-ascii?Q?VRjddf2aPTlObTQ8oq9SAfqB0r7KLmGGTVXhpBJWxIC/+Is5uH6wT/vXMpI9?= =?us-ascii?Q?TspQJyv2HZHWNwqT08ixJBaupFXZ3rSJI2vKW4Q7J5iZjCeMhki+g2j7X3OA?= =?us-ascii?Q?IkqNo6S/yEivuGnh7wNnmwsaU/yGcExwZz1T2lN3pFyJc7AWLfL1xWR+On4U?= =?us-ascii?Q?5EqcTUtX7DLh2zgJfzASitsfOPfkMbm8/WwxPsreyzrvTxdu7OttbT5+Ro2b?= =?us-ascii?Q?rlhniyccHtSLn6SHmrlBx5Vkl4OJU0/acIfXRV24MqZWFXY+QrgcPTkoiLNN?= =?us-ascii?Q?TnyJXpmt0zRrRgPrcP6qLYQ88227sjQ9MYsdAju/cDdSUeS5ItWy1bKZ/EKG?= =?us-ascii?Q?MGnJ3Zr3ZsL16Du3/ULHET9hqHFvBuJDhvDKzC8jrgLTdcc+aAD6Bl50Bw79?= =?us-ascii?Q?O+3P2YRylEwdHtT31Rl3mJCKemo78QNhrW0cEvwfz0n5qenU0gB63bl6LGIk?= =?us-ascii?Q?SUGWMCu3TpZqursl+PObg8P5RnAtyFkDhS6AHsycRcGpj5fC3Aw3gRc1//Rw?= =?us-ascii?Q?u1Wjo7nXlNtFR0R21kbo7Yh/gk04ZzxAcX/HCq8pm2seD8o8hECVAB7ZN87q?= =?us-ascii?Q?LJIl+yvIPc1k8NRLEQIim1fcP5Q3fNnbvuZhWEu6OfAeFT/sbit3ZohM7+vg?= =?us-ascii?Q?zVdP3y7qhvHbza+nZiqebA/dWHpIAT15nrSZUhnMjegc/zw6NzYzCQNfQ6m1?= =?us-ascii?Q?vc/cGVzgpUHW6UDuwTAqrEMmQpUegFlh4KEgY3pU8J6mKaVwB7a4wnqCl4TC?= =?us-ascii?Q?cjbdNul5vIItOLtjdEN03P5wyq8T5CIQkjr13t8pWIL/V3qaCZI4zJ6GgajT?= =?us-ascii?Q?RQE+sVShugLztySpVS7EALxlQOEcnR/wdox2COwH2TPG9D86QuRgiOS7OINj?= =?us-ascii?Q?hOv9hHd5adePrrtIda/V869NEdH8FgIGc9MWpM+8iVcknzBysqb6z7fa/+9i?= =?us-ascii?Q?kzXRpbI7htreEOg77W8/IEaRQY9JiVyS4f33c3/08KEYrDI4i70C+6BgZ+lM?= =?us-ascii?Q?7fQwXJzEQtsWtMA1NBgEiJFrprK8Lu8akXEJmIGhYg0miRGhHz+Ij/jqelAI?= =?us-ascii?Q?w8wZ3MFCKZo3c8lCDt3mg7qsOiXqjbItp/kyAQmwzgo832iDdaAEWQ01BSTn?= =?us-ascii?Q?S843TT6N850mA6XY1xJVyxNeUYgqJlusbSrOQj/c?= X-MS-Exchange-CrossTenant-Network-Message-Id: 21147dcd-d567-4373-29bc-08dd71833abe X-MS-Exchange-CrossTenant-AuthSource: DS7PR11MB5966.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 02 Apr 2025 01:10:59.8367 (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: 3Bo8NDcHaUM9wYnq4hvSOtU12Qi/fqBzwg5/6acvK+UW/A7QxblUYyp1j7CHI0ycEceQIb3tIyPXZrKUHnOkWw== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS0PR11MB8739 X-OriginatorOrg: intel.com On Tue, Apr 01, 2025 at 05:22:38PM -0700, Sean Christopherson wrote: > On Wed, Apr 02, 2025, Yan Zhao wrote: > > On Tue, Apr 01, 2025 at 03:11:07PM -0700, Sean Christopherson wrote: > > > Add back support for honoring guest PAT on Intel CPUs that support self- > > > snoop (and don't have errata), but guarded by a quirk so as not to break > > > existing setups that subtly relied on KVM forcing WB for synthetic > > > devices. > > > > > > This effectively reverts commit 9d70f3fec14421e793ffbc0ec2f739b24e534900 > > > and reapplies 377b2f359d1f71c75f8cc352b5c81f2210312d83, but with a quirk. > > > > > > Cc: Yan Zhao > > > Signed-off-by: Sean Christopherson > > > --- > > > > > Hi Sean, > > > > > AFAIK, we don't have an answer as to whether the slow UC behavior on CLX+ > > > is working as intended or a CPU flaw, which Paolo was hoping we would get > > We did answer the slow UC behavior is working as intended at [1]. > > > > "After consulting with CPU architects, > > it's told that this behavior is expected on ICX/SPR Xeon platforms due to > > the snooping implementation." > > > > Paolo then help update the series to v2 [2] /v3 [3]. > > > > Did you overlook those series, or is there something I missed? > > Nope, you didn't miss anything. I have that series in my TODO folder, but only > glanced at it when it flew by and completely missed that it quirks ignoring > guest PAT. Not sure how I missed the cover letter subject though... > > Anyways, ignore this, my bad. Thanks for the update, and sorry for the noise! That's OK :)