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To: Reiji Watanabe Cc: linux-kernel@vger.kernel.org, x86@kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, Jonathan Corbet , bsd@redhat.com References: <20210430131733.192414-1-rsaripal@amd.com> <20210430131733.192414-2-rsaripal@amd.com> From: "Saripalli, RK" Message-ID: Date: Fri, 30 Apr 2021 14:52:08 -0500 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.10.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [165.204.77.11] X-ClientProxiedBy: SA9PR03CA0005.namprd03.prod.outlook.com (2603:10b6:806:20::10) To DM6PR12MB3435.namprd12.prod.outlook.com (2603:10b6:5:39::26) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [172.31.9.26] (165.204.77.11) by SA9PR03CA0005.namprd03.prod.outlook.com (2603:10b6:806:20::10) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4087.27 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData: =?utf-8?B?RE12OGV3RldaUGtFbm42RnRwNlcwaUc0LytsOGtTTGQwQmp5OVhSQ0pQZmxE?= =?utf-8?B?Mnp5YVRobjZvcER0Ym9RS0Zid3h3aDhJSVc0RnZXMjJxQ045M25pNE8zNndX?= =?utf-8?B?NjZ4NFl1UHRndEk5Z1ZlcGxybWJRTlVBblFNYnpzSFZWenF5Tm1QSWVhcTVU?= =?utf-8?B?dERSaXBwSUZOaFZGYjhuMmRHZTlSaEZCQXNXSm1Nempvd2hFbExUcFVrZjgy?= =?utf-8?B?Z09jV3RKaDFYbThSS2NiY1B1cFhsTkczQnJSeW1LU1RlK1c0ZUVpU0tIN3or?= =?utf-8?B?RFNCUkxkYU9iSFdybzdxb2hiUGtIMkMzaXg3aDRyRnc1a0Z4K2d6UkthZW54?= =?utf-8?B?TUNuMzRDYUh4d0lIYmkrdjBRMUtWSXhnNEVIeU5FL2ptQnRYZm9ZdkZNZEdu?= =?utf-8?B?UXNnS1ZNQ0s0dE1JUklXendSOHhDckhUYml2V2lOL0lXWHRFSzdMSHFpZit1?= =?utf-8?B?NVhFaHhzdDdpZ1N2SWdpSFF1bE9kclRvNHBIMTZjWi83L3FBZElzU2FQOE4y?= =?utf-8?B?TUgwbnhTYjdCTGNWaXczOThnSVBYUUpYdm84ajRrYUx5M2pWbXZYSWMwRlMw?= =?utf-8?B?bjZRRmxrU2JZK3ZaRDZ6b0xEN3pnbDRaOXRTcllWb2s4QXlSSWNuNTJaWFp1?= =?utf-8?B?UC9WOXQybW1vSW1kMUl2dUF2aEtpQU1pbjV5Zlg2TjlaK0kxTi9hMmE3VDRE?= =?utf-8?B?NVBaa0VZWGw2OVVPWXhJTXpFYW43TmFqR01Wb3NaZjRyaHJHbDlFMHFKRGhq?= =?utf-8?B?NUFvQy9nK1NoQm1BeVlEVnYwTE0zMGg0TGlLOHIxY3pGMGJRMWcwUzE5TEtO?= =?utf-8?B?ZXJ0U04zT2NVWjlqZFZnaHUra2d5VWtZRUpFQnVicUdqcmYrTzUvUk1sRHVJ?= =?utf-8?B?NU12aFV0NUdhR29XUVNxM1VQVTFIY2lJcHZzK2MzZ2JHM1B1TlZldG1Oc0ZJ?= =?utf-8?B?U09xR3BEOVU4WDlNaXRlR1lTQVczWm9XellnU1pRZzZJRnBWRzNKaGk1WERG?= =?utf-8?B?UXVzd3RSYXl3ZGMwdnIrQUt0djRESTBVQXVMWTBPejU3UjNPUU5TUCsxU1kx?= =?utf-8?B?T1duV1RZRGxrMlBZcFdPd1lrcUpXNnBXRDR2SHBES3RrcTcvNWZnTkYvQWFY?= =?utf-8?B?L0RnRVVKUDJiUVpRTStYR2cwZW5sRXQweFdDSGVVMnFVQncwQTVyZWhOOHZT?= =?utf-8?B?YVl2WUdaU3lKQm9SMU9ZU3hnc3pZaUZtL0FUTnl4UEJRUmlHUXVoUjVrUm9U?= =?utf-8?B?QUV1SzNFRG1uWHFMK0F6TjdjdU54K0N1aXhLaDhPaHJTSkFSekY1Yk9ISXhD?= =?utf-8?B?eFlnVlR3R0dSQmFXWVhLM2VRSDFyWmM3SDZTRURXNjlSWkdCazdkRU9KanJ1?= =?utf-8?B?V1RIREtKVTJKcU5zVGZYMnk4azUrVlB3MVZwWmtBaCt3Rmovb2IrZWJKTWZJ?= =?utf-8?B?T1h4bCtxOG1CUU5qUnhzK0g4TTZoL2F3eTJML0E4L1VsQlQrNFd5MXpCUWNR?= =?utf-8?B?UGxmbmRyMVM0Qldpd2xtREU2VjVoTU8xWXJSWnJNdHFSTjhXc0xPMTRlWk5P?= =?utf-8?B?QmxyazdrdGdQejg0c1gydXhpSitQNlVFVmxFZ2UxWlpoSjBHVVRONWRQMTZj?= =?utf-8?B?Qk9scTZib25Qa1IzTTkyVUtOcWQwdFJiOEwxbGpLUWJEUEdnaHBQY3RSTk9L?= =?utf-8?B?OTNkVExzd2Zia0sxVWo0cDFUNUhMVGIwYUNhdVFpQU52eFE3anF0RTVnTTg4?= =?utf-8?Q?KpD5KWlrygbPZzRdTDt9dUhW84rlQXfMVh7EoUX?= X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-Network-Message-Id: 5a1b36aa-730b-4338-ca56-08d90c1171d9 X-MS-Exchange-CrossTenant-AuthSource: DM6PR12MB3435.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 30 Apr 2021 19:52:11.5050 (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: mo8oXqHiuzN5c0Se6kxM8AL2IZyZl0iZN/TQRR9SUPWNYU/xTl8fPh37PjZz6aUTU2SSwUok7tBYal+qnj5KGg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM5PR12MB1195 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/30/2021 2:42 PM, Reiji Watanabe wrote: >> +static int __init psf_cmdline(char *str) >> +{ >> + u64 tmp = 0; >> + >> + if (!boot_cpu_has(X86_FEATURE_PSFD)) >> + return 0; >> + >> + if (!str) >> + return -EINVAL; >> + >> + if (!strcmp(str, "off")) { >> + set_cpu_cap(&boot_cpu_data, X86_FEATURE_MSR_SPEC_CTRL); >> + rdmsrl(MSR_IA32_SPEC_CTRL, tmp); >> + tmp |= SPEC_CTRL_PSFD; >> + x86_spec_ctrl_base |= tmp; >> + wrmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base); >> + } >> + >> + return 0; >> +} > > > Shouldn't X86_FEATURE_MSR_SPEC_CTRL always be set if the CPU has > X86_FEATURE_PSFD even if the new kernel parameter is not used ? > (e.g. set X86_FEATURE_MSR_SPEC_CTRL in init_speculation_control() > and have psf_cmdline() do the rest) > > Considering KVM/virtualization for a CPU that has X86_FEATURE_PSFD > but no other existing feature with MSR_IA32_SPEC_CTRL, if a host > doesn't enable PSFD with the new parameter, the host doesn't have > X86_FEATURE_MSR_SPEC_CTRL. Then, it would be a problem if its > guests want to use PSFD looking at x86_virt_spec_ctrl(). > (I'm not sure how you will change your previous KVM patch though) Reiji, you are correct that X86_FEATURE_MSR_SPEC_CTRL should be enabled so KVM guests can use PSFD even if host does not use it. I have this change in my KVM patch. Thanks for the review, RK > > Thanks, > Reiji >