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Thu, 14 Jan 2021 20:57:53 +0000 Cc: brijesh.singh@amd.com, Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Borislav Petkov , Tom Lendacky Subject: Re: [PATCH v2 01/14] KVM: SVM: Zero out the VMCB array used to track SEV ASID association To: Sean Christopherson , Paolo Bonzini , Dave Hansen , Andy Lutomirski , Peter Zijlstra References: <20210114003708.3798992-1-seanjc@google.com> <20210114003708.3798992-2-seanjc@google.com> From: Brijesh Singh Message-ID: <6d329b0c-e34e-6fed-8cc5-10b9ece82409@amd.com> Date: Thu, 14 Jan 2021 14:57:51 -0600 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.6.1 In-Reply-To: <20210114003708.3798992-2-seanjc@google.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US X-Originating-IP: [70.112.153.56] X-ClientProxiedBy: SA9PR13CA0079.namprd13.prod.outlook.com (2603:10b6:806:23::24) To SN6PR12MB2718.namprd12.prod.outlook.com (2603:10b6:805:6f::22) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from Brijeshs-MacBook-Pro.local (70.112.153.56) by SA9PR13CA0079.namprd13.prod.outlook.com (2603:10b6:806:23::24) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3784.7 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData: =?utf-8?B?RXFROEVjQm1PZFFDTkpDZ09zS2NvWmZsSjgxemU2T3FuUDR6MkJoSGd6cjdB?= =?utf-8?B?S0xhdlBuQ0ZETU44TVRGSUxhM2RRRUdvQjFncGxpRXA1Qi9hWjFqZjQ0T2Jz?= =?utf-8?B?NlhxNzFPUEVQU2cybVhvOW1VSTkzaEh5cXdPajNnZk1EVFVhU0JhQzdocWhF?= =?utf-8?B?R3VSemQwb3BnMHFwVlBMYzhHN2hKNVlNMkgweG9Tbk1RdlRoc25MK1ZRdkpH?= =?utf-8?B?K3JhcUxsNTZKck8yMW4vT3k2Y3hRbERHbGpONmp3UEtJOHY0Wjc5T1QwNnM3?= =?utf-8?B?bG9xVTUxNFNsVmhVOWNCSVRmcm9VRDNwM2tQWFlFbXh6M0o3Z2ZtbHV1QmJm?= =?utf-8?B?cXFTNGRvUlRQNUE2VE8vbjErZGt3aDh5MFFUdzZ2N3RUZFJJQzM0V3UyWWJY?= =?utf-8?B?ZGhDUVdUbGFlYnJlQmxKWlBSQ1ViYll1Nlc4QTZ2QWZGcXdCV3phd1I5ZzND?= =?utf-8?B?Z094TnBOWGkxZjZDcmFsYnZlMUhCa21Sbmp6T2tvL2RTMGI2dmZ3MlljR051?= =?utf-8?B?Qk0xRVNFRUpITm94Z1ByTC9OdG1aYm1aWjc2bzBqUG4wM3c0cEdaNFYwNnZu?= =?utf-8?B?MFB0b2FYSGROcEM2VDhrNU1vdjVTemZiSWxVaDhRZnQvWlRQdzJibitTa21s?= =?utf-8?B?Z2ZMTEpRYnY3UERJZm9sa1B3QndDelcrZ25tTnBZRzVWSThrbHV6MVRMZENF?= =?utf-8?B?Ly9qeWJkdFRxRWdzR2VER2NEQmloSHdJeUJ6dk1GM0t3c3hxRk9ZL1NpM2hv?= =?utf-8?B?a0szUUQrRDl6VW1zWkMyaEJNbmxFUi9UR0sxRUllY3BObVNOcjFEQ0ZqckFl?= =?utf-8?B?VFdjUTBCMmhmSlVmd2krcXRmUk10MFVESEZXVm9hQUw3eUxHMTl5N0pxYm81?= =?utf-8?B?U2dPQk9aemlSSmRYS1NicjB2KzdXeWhzN1JDd2UvUDZHeEFuN2VYdTJMRXhT?= =?utf-8?B?MUNFcmFZRkN3WFN4RGE3WUZyeXdsMGlOZnFnbHVlODdncTB6ZkV4aUdUYUIr?= =?utf-8?B?YzlQRVFZdWxTQStxZ3M3SVUxNzRBb0tKaC9xWGRWYUMzbk1YMkk3L1JmaXcv?= =?utf-8?B?d0l4Y2hHd05pVm9WTWo0TndZZ1AyL0lXQmFlNzlQbEpvM1pTck9WZ2RCUCtZ?= =?utf-8?B?WGNEWDRIL2xsaXpZTWlYVjlONEVHbHNKL0x1dmtNakh1Vy8vdHBGYWFFWkdP?= =?utf-8?B?RTFaRERrYjJLQVh2NnRlL1MxZjdsS1Fucm95dWY5ak8yanJWWnJ1TEJXS05J?= =?utf-8?B?U2lpKzNVQkJkOTA3STRIc1IrNDRvQzRITTNVU2VFOGpmN1A4SUJ5L29mWnB2?= =?utf-8?Q?KkFfQIG7mgQua1KOej37KVm5QhZrkK+Dqr?= X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-AuthSource: SN6PR12MB2718.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 14 Jan 2021 20:57:53.1263 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-Network-Message-Id: 24b2cc73-94e3-464b-2983-08d8b8cf0f92 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: eBp2BM/IreevUB0Zkse9MGoMw7Y22W8yGNSc7/dUYW1vM+tvczRbXUZKYQunQ1PqMijr68rUnkLvnmLy9HtuIw== X-MS-Exchange-Transport-CrossTenantHeadersStamped: SN6PR12MB4750 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 1/13/21 6:36 PM, Sean Christopherson wrote: > Zero out the array of VMCB pointers so that pre_sev_run() won't see > garbage when querying the array to detect when an SEV ASID is being > associated with a new VMCB. In practice, reading random values is all > but guaranteed to be benign as a false negative (which is extremely > unlikely on its own) can only happen on CPU0 on the first VMRUN and would > only cause KVM to skip the ASID flush. For anything bad to happen, a > previous instance of KVM would have to exit without flushing the ASID, > _and_ KVM would have to not flush the ASID at any time while building the > new SEV guest. > > Cc: Borislav Petkov > Cc: Tom Lendacky > Cc: Brijesh Singh > Fixes: 70cd94e60c73 ("KVM: SVM: VMRUN should use associated ASID when SEV is enabled") > Signed-off-by: Sean Christopherson > --- > arch/x86/kvm/svm/svm.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c > index 7ef171790d02..ccf52c5531fb 100644 > --- a/arch/x86/kvm/svm/svm.c > +++ b/arch/x86/kvm/svm/svm.c > @@ -573,7 +573,7 @@ static int svm_cpu_init(int cpu) > if (svm_sev_enabled()) { > sd->sev_vmcbs = kmalloc_array(max_sev_asid + 1, > sizeof(void *), > - GFP_KERNEL); > + GFP_KERNEL | __GFP_ZERO); > if (!sd->sev_vmcbs) > goto free_save_area; > } Reviewed-by: Brijesh Singh