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dkim=none (message not signed) header.d=none;vger.kernel.org; dmarc=none action=none header.from=amd.com; Received: from MW3PR12MB4553.namprd12.prod.outlook.com (2603:10b6:303:2c::19) by MWHPR1201MB2526.namprd12.prod.outlook.com (2603:10b6:300:ec::7) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4544.18; Mon, 27 Sep 2021 15:47:04 +0000 Received: from MW3PR12MB4553.namprd12.prod.outlook.com ([fe80::41ef:d712:79a2:30c1]) by MW3PR12MB4553.namprd12.prod.outlook.com ([fe80::41ef:d712:79a2:30c1%6]) with mapi id 15.20.4544.021; Mon, 27 Sep 2021 15:47:04 +0000 Subject: Re: [PATCH] KVM: x86: Expose Predictive Store Forwarding Disable To: Paolo Bonzini , Borislav Petkov Cc: tglx@linutronix.de, mingo@redhat.com, x86@kernel.org, hpa@zytor.com, seanjc@google.com, vkuznets@redhat.com, wanpengli@tencent.com, jmattson@google.com, joro@8bytes.org, tony.luck@intel.com, peterz@infradead.org, kyung.min.park@intel.com, wei.huang2@amd.com, jgross@suse.com, andrew.cooper3@citrix.com, linux-kernel@vger.kernel.org, kvm@vger.kernel.org References: <163244601049.30292.5855870305350227855.stgit@bmoger-ubuntu> From: Babu Moger Message-ID: <14993859-b953-b833-cdf2-ff2e29e9044d@amd.com> Date: Mon, 27 Sep 2021 10:47:01 -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?TkhQQTl1ejVGWVhMbGFtT2FsRGJzbSswZGt3anJMQmI3NWJjNzkySHlPR3Nx?= =?utf-8?B?NmgzT2ZiSGhybWcwRXE1UGVxTmg0UUhHTlJCUzlGc2g1aUw0WFRxN2JGVGJw?= =?utf-8?B?S1Vra3pidml5OHhxZHlWNG5zN2ZPejl3a3RkYmwxdTlrN09iUUo4YkhyZHJP?= =?utf-8?B?SnpIZHlCMndVbk90Nk13VVZoTGs5ajZrekJORXNGNUMweFVZWWV5TG4yQVlL?= =?utf-8?B?SDREUGxub0srWVNtc2JxbFVUbXFlQ0syWjFUbENzaDRjZlZuS3czRytMK2Vs?= =?utf-8?B?SDRxWUlvQy9RTlpTOEsvUDIvUXM5RmY0WkM2Nm9IeHJPUGJTczJvTlVuWFZQ?= =?utf-8?B?MmZmWnVyZm1sOGRVZ3VmOUJJbFBUK0VoNkhFQWRPSHRpMXFjSU8xaXZFeFk2?= =?utf-8?B?N3NjYTR5SUk5REw3aTdwWXAvYUNIY2xDN0VpZjhFeWRpUnkrd0ZXYkZ5K25O?= =?utf-8?B?RlJIVlNqY0ZzYnFZNXhDWTJnZFhoL2dxQStFUE1HU0dZRkI4b0ltVzNZSU1W?= =?utf-8?B?YXN1dXNta3plUDhHang4aTZGeTU4K2wvV0RCUk1aSUYwYWFzREpqLy9NQm52?= =?utf-8?B?WWZwVE45WXJ2QmRZWmpmMEpmQld0NFB5UXlsc053bzBUUnNBKzBSTTZ5dVVM?= =?utf-8?B?dkZ4WTdyQmZjNWl3MkNPb1BiN3lXRjlxOVpCcFRYTkFVeHp5NEZ1QjBUZVlI?= =?utf-8?B?WHloKzIxQlFLQktFVmJ1cUVtUGNWb2h4QTBjM0ExMklia0t4YTVUcTRyeHRB?= =?utf-8?B?V3dMZEpsbDJLNURmWW1McW44RmMwWGJoeHl1cnNCVjdhaDVhWDlKY081SVVt?= =?utf-8?B?bUh2TEE1MmRjVDNDREFSeTQ0Vk0rOVFNaS9JRUNiZFQ2VHVqZmlZTTlycG9y?= =?utf-8?B?U1BzR1liZ3NzZWlxVmp2SEFzVmVUMkZ3cFZiYldMWGZDdmw2S0hLenZ1SXBC?= =?utf-8?B?MDF5eVdrK3Q0U01Fa002SkgxbVN6aklDVXljeFo0UU9vWEUzOFM2blFuODd0?= =?utf-8?B?OEpHcFduRjJheG1pWGxoL1ZtNHFra242R09oM1BVL0loVlRxdEN6TmFYNUFF?= =?utf-8?B?eks4bjhvbnNRMWoxbmVEdm15dUI2dVM3ZkpKaGZkOS9jMytQa2lhTUlFSHE4?= =?utf-8?B?RWNEd0FIRHdTeUJyU3dteUY0dUZadTBqay9VS1RvZTY5TjdtdWRNWGtDZHFB?= =?utf-8?B?dlNpbkc0NTBFcTdXQWhocy9zYmN4SHkyNDN2b1pvYk9rVXRoK3NRbWw4RUNQ?= =?utf-8?B?QWZyR3dLMkJ5UUFuMjhvWXJnd2IyVUpsczZtb1RGNUxGS3BXVktXa2VPNEV6?= =?utf-8?B?OFRoZy9XNG8wS0cwdXNtNmpEOERsbVpuYStVb3dPOHQrSk41dVJSSEpyUmNw?= =?utf-8?B?dHUyZUE2Q00vakFXSnQyU1NsVVNqNjRzNjNMb1Z1WVBXbmxFNFFacWhvdjZK?= =?utf-8?B?WlByN2lKT01wOUZTSU1ybE9aSTd4QnBPUUVBdmhmMTA1aHd1UFhURUFESjZk?= =?utf-8?B?OU5XaENiTTZTTit1YkdCQmhvMlIzZmNmVjJ0THlmcWpkbFp0aWV1RmZGRDUr?= =?utf-8?B?eERNclhaTFlKY050WVB6YmllcXRjVXdhU3QrMmkzb2JXTUgvNkpRSkp0MUtn?= =?utf-8?B?SnhIY2liY29lMDJEa29IQWJLcVJyMEFUSEEvaEprellvUmljS3ZuK0EzckNZ?= =?utf-8?B?KzBZZE1hK1ViRkw4d2IxbStEMXgxSnRjSnRDL3Vyek05TWY2b05tZzhWNGxR?= =?utf-8?Q?702h0YrjQLLv+xVbsh8CQKj5siMxD4lwfzx4sBb?= X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-Network-Message-Id: c108b940-f9fb-497e-8fda-08d981ce0d6c X-MS-Exchange-CrossTenant-AuthSource: MW3PR12MB4553.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 27 Sep 2021 15:47:04.0231 (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: sDic3f8MAuRuCj1BdOgowaKro8yspq2achh9AnrAAWQcodZBkKiFUSK7buH/VSVo X-MS-Exchange-Transport-CrossTenantHeadersStamped: MWHPR1201MB2526 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 9/27/21 7:54 AM, Paolo Bonzini wrote: > On 27/09/21 14:28, Borislav Petkov wrote: >> On Mon, Sep 27, 2021 at 02:14:52PM +0200, Paolo Bonzini wrote: >>> Right, not which MSR to write but which value to write.  It doesn't know >>> that the PSF disable bit is valid unless the corresponding CPUID bit is >>> set. >> >> There's no need for the separate PSF CPUID bit yet. We have decided for >> now to not control PSF separately but disable it through SSB. Please >> follow this thread: > > There are other guests than Linux.  This patch is just telling userspace Yes, That is the reason for this patch. > that KVM knows what the PSFD bit is.  It is also possible to expose the > bit in KVM without having any #define in cpufeatures.h or without the > kernel using it.  For example KVM had been exposing FSGSBASE long before > Linux supported it. > > That said, the patch is incomplete because it should also add the new > CPUID bit to guest_has_spec_ctrl_msr (what KVM *really* cares about is not > the individual bits, only whether SPEC_CTRL exists at all). Yea, I missed that. Will add it in next revision, Thanks Babu