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Peter Anvin" , Dan Williams , "Kirill A. Shutemov" , Tom Lendacky , Jane Chu , Tianyu Lan , Randy Dunlap , Sean Christopherson , Juergen Gross , xen-devel@lists.xenproject.org, stable@vger.kernel.org, linux-kernel@vger.kernel.org References: <9d5070ae4f3e956a95d3f50e24f1a93488b9ff52.1657671676.git.brchuckz.ref@aol.com> <9d5070ae4f3e956a95d3f50e24f1a93488b9ff52.1657671676.git.brchuckz@aol.com> From: Jan Beulich In-Reply-To: <9d5070ae4f3e956a95d3f50e24f1a93488b9ff52.1657671676.git.brchuckz@aol.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ClientProxiedBy: AS9PR06CA0653.eurprd06.prod.outlook.com (2603:10a6:20b:46f::33) To VE1PR04MB6560.eurprd04.prod.outlook.com (2603:10a6:803:122::25) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: af25e754-b29f-4d9b-e49d-08da64977493 X-MS-TrafficTypeDiagnostic: DB7PR04MB4892:EE_ X-LD-Processed: f7a17af6-1c5c-4a36-aa8b-f5be247aa4ba,ExtFwd X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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You've sufficiently altered this change to clearly no longer want my S-o-b; unfortunately in fact I think you broke things: > @@ -292,7 +294,7 @@ void init_cache_modes(void) > rdmsrl(MSR_IA32_CR_PAT, pat); > } > > - if (!pat) { > + if (!pat || pat_force_disabled) { By checking the new variable here ... > /* > * No PAT. Emulate the PAT table that corresponds to the two > * cache bits, PWT (Write Through) and PCD (Cache Disable). > @@ -313,6 +315,16 @@ void init_cache_modes(void) > */ > pat = PAT(0, WB) | PAT(1, WT) | PAT(2, UC_MINUS) | PAT(3, UC) | > PAT(4, WB) | PAT(5, WT) | PAT(6, UC_MINUS) | PAT(7, UC); ... you put in place a software view which doesn't match hardware. I continue to think that ... > + } else if (!pat_bp_enabled) { ... the variable wants checking here instead (at which point, yes, this comes quite close to simply being a v2 of my original patch). By using !pat_bp_enabled here you actually broaden where the change would take effect. Iirc Boris had asked to narrow things (besides voicing opposition to this approach altogether). Even without that request I wonder whether you aren't going to far with this. Jan