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Thu, 14 Jan 2021 15:56:42 +0000 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 Cc: Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Borislav Petkov , Brijesh Singh References: <20210114003708.3798992-1-seanjc@google.com> <20210114003708.3798992-2-seanjc@google.com> From: Tom Lendacky Message-ID: <3d41137e-e8e0-8139-3050-eac58ad82a4f@amd.com> Date: Thu, 14 Jan 2021 09:56:39 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 In-Reply-To: <20210114003708.3798992-2-seanjc@google.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [67.79.209.213] X-ClientProxiedBy: SN6PR04CA0081.namprd04.prod.outlook.com (2603:10b6:805:f2::22) To DM5PR12MB1355.namprd12.prod.outlook.com (2603:10b6:3:6e::7) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from office-linux.texastahm.com (67.79.209.213) by SN6PR04CA0081.namprd04.prod.outlook.com (2603:10b6:805:f2::22) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3763.10 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData: =?utf-8?B?TU9ITi9lc1RDVHVhZENWZ05ITVduSU5WZElvWlNEU3VwaEMrRHBza1FCOEJC?= =?utf-8?B?b1JOMXNubjdGamRTUTh0Y0VKdERlMHNZbEQvWFNUV2FWbG5xazMzamszM1hI?= =?utf-8?B?V0t5UUxqWTBKRXpxZGR3MmxyZkx1dUJLeEdwc2FzVXNuUTRrV2haNEVoTkli?= =?utf-8?B?NzROTVNBYXJBclYrMUZWSVh6ZlFCbS94N2dGd2tRMUwrSUtBMUJVNWY4eWVO?= =?utf-8?B?SFc2YlVGaEcvOWZEWmNFY0VubkpRdmlYNXNzbC9mSGlYTHdlVFJudkRnZ3Iy?= =?utf-8?B?NEVFVm9NYUxXeDBBZGR1SE5EVEh1N09hTXd4NXdkUXltUVdsV2pqUFZqa0NH?= =?utf-8?B?a3BITWdSREpIL3RSa1VtVG0xV0xhM3d1bUdYZndCQzB1UU54bjRYWWplR2VZ?= =?utf-8?B?UFVKNzhiRVo0ZHBrQ1R1NGZsMERHdlJpZkJrNGIxSHB5azZtNlZpdS9pNHRw?= =?utf-8?B?eEw4cCtDd1diMGFBR2ZjVlVEL3ZJQ1ZQcURERTFMWDVvdHB0N203ZVFYanZE?= =?utf-8?B?T0NsMGRvaHh2M1R5ZVdBNUNBOXFSUVNNSDd3Y2lWb2ZNMzlRZ2RXVlg3cWJC?= =?utf-8?B?NW5PN0lNYWV3ZE1BN3ZjdGZnTGZNT2ZRaGdiaVFBVkVldk1sV1FsSEk4WmRk?= =?utf-8?B?dlo1aFhZaFp0U0c0MUIwdmU1TUFCTGxlSXQ1NjFXM01SbXZiNXFwQXhra2wz?= =?utf-8?B?SUtIaktEY1ZlWndVcmoxRlVMOTh4cnZLcVFXcHRabkg3TG5MN0szbUsyRUJu?= =?utf-8?B?aytsNjZQbXl0SnRzT3JwMEI3b1VCMXc2VDV0YXNoa0ZibFZwYnIvOTJSUm5R?= =?utf-8?B?ZVMweXI1bjJmQ1dPcngwV2JDSnVqaXVvK3lNbWZEcDd6aGdGZTJBYzdDcXo5?= =?utf-8?B?RFFucGlMWGFZSTFUclp0SjFEM21PZm9Cc0ZhOERPcmU4bnhkc1J3K2NZUjlL?= =?utf-8?B?RHBkNEhieDhTQ3JkRll6VUV0L2Iva0dzNHpxMms0aVlDbUs0ZHd4SmhGQ1Uy?= =?utf-8?B?aHQ2QVJKc1FlOHZFbyt1NXpaTnpKNmZLaFdrUlFGZVUzWGdXMVlYZ2pUVTNv?= =?utf-8?B?Zkg4YWRQeSt2OGdTQXYvSGV5cytBM0hSRWFmRVI5ZnpEM0IrbG5mSnVWSi81?= =?utf-8?B?cmJ3K3J6N2o3QjlTZzFqZnVJTjVwSlAxZjNHODd0U3RHU2VVUFBaMWpFUnRy?= =?utf-8?B?bUV3c2o2UWhOWENWOGlUM3kwd3N1OWFJMFhlZVBybXNnVkN5OS9kb2s3Q1c4?= =?utf-8?B?dkxnUjgxcUowcFZVSHpLZ1hsTTVuTnBKVHVEUUkrR0dpYW5wMDV0bXNobVJl?= =?utf-8?Q?iOOYdUGDaOup552fX13f1oca4D8zJA+Bcs?= X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-AuthSource: DM5PR12MB1355.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 14 Jan 2021 15:56:42.3520 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-Network-Message-Id: c96579a0-23cf-460e-8597-08d8b8a4fc8c X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: 50C2xJpybELVCHPRzAyquYC6PK8GkKfmGmOiT2gYRLmv/5jyq+XILckpKcUBPc/ula+YmDY9x1oSF4/sXiHDGw== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM5PR12MB1708 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); Alternatively, this call could just be changed to kcalloc(). Either way, Reviewed-by: Tom Lendacky > if (!sd->sev_vmcbs) > goto free_save_area; > } >