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Fri, 6 Aug 2021 08:36:07 +0000 Date: Fri, 6 Aug 2021 11:35:49 +0300 From: Dan Carpenter To: Joerg Roedel Cc: kvm@vger.kernel.org Subject: Re: [bug report] x86/sev: Split up runtime #VC handler for correct state tracking Message-ID: <20210806083549.GM22532@kadam> References: <20210804095725.GA8011@kili> <20210804125834.GF22532@kadam> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) X-ClientProxiedBy: JNXP275CA0020.ZAFP275.PROD.OUTLOOK.COM (2603:1086:0:19::32) To MWHPR1001MB2365.namprd10.prod.outlook.com (2603:10b6:301:2d::28) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from kadam (102.222.70.252) by JNXP275CA0020.ZAFP275.PROD.OUTLOOK.COM (2603:1086:0:19::32) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4394.15 via Frontend Transport; Fri, 6 Aug 2021 08:36:03 +0000 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: bd81fe17-3352-4d50-8914-08d958b53bef X-MS-TrafficTypeDiagnostic: MWHPR1001MB2205: X-MS-Exchange-Transport-Forked: True X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:9508; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?pOkT2/lChcc1e8qUpVk8QnExZuLv2zES2PHI/vhnTJO/mhReyiiEQ07MlsNd?= =?us-ascii?Q?gGFMMVu8FzNVmtQZ1VFbeJrnVwh6cx86O6Dvw76kl2nkZNWxgwS37po7ugbU?= =?us-ascii?Q?52ExRxnY0ukm2sBGFLsaYpLimj72NrSrF4XGn0BVvRDAKvVD5mryhcFnxW7y?= =?us-ascii?Q?VkpSKvx4VW+D5awylzKH4Hs7U888ZYEMfHbaxk9ZUsZVBkjvyleH++nj2o+5?= =?us-ascii?Q?a8Al8h5yVkcB4An6i4lfVq+TW9U0/oo7vg8pcxxmQaT129huIdlsN56ksSAu?= =?us-ascii?Q?yk1V6fJ34BtwaCUdt23pKGPuC9/SSj+EXRcVev9VRG3ATRfHUhPH8AVIjOYe?= =?us-ascii?Q?PPO83AVhg85Ytj7Qg+JQXy+bOO5Wue7TleLdJU0mL8KNeG5346kE/GnR0ka4?= =?us-ascii?Q?XLTsgcU/IDRDCtYSwM9gMwwl1WsJyAqUMWjRPvhxhsJz0JbzQu853V1vbnLw?= =?us-ascii?Q?pCLwTTubnPYsYzQmsc+TtT2mJ0nlfJjrfk2iFVyHHbh329SbGKHCu0mh9YMe?= =?us-ascii?Q?0n6p2Q+RnY4S/pCl7qgboNmgGZhGtVGoIofWkxhzKLqE0BoGm/cVlUS4VyQC?= =?us-ascii?Q?GKNPhr2JMHyTjbMVdXQyhR1twuRp14/K9fInF5XdySScUXEtGwIijdzfwrhK?= =?us-ascii?Q?pzmlQXstnf0dAOri+6fLi+VTPAPPpO3qT3s71OQZHgeNXzeYp8lodk9Gyfcm?= =?us-ascii?Q?JYoyXBYrr3lWjPj8/zswehcE07aTW5m5fajpWZ15UgscOnNgXxAQDtwuF5Sf?= =?us-ascii?Q?Te9WkpSxDbjnD6a9aypwUkfQuD3K41THNynN0RYCr6gYCf9ZvYvE56pHWv5V?= =?us-ascii?Q?/s0dZAHym3CBc8My/XYhYleRL3lTjF8L5pNJOsf/vvpKC1ZW87eF6ze1R98s?= =?us-ascii?Q?V3Pctb3oPEh+0VL/NKUQBE8ozz0iPG04Ks9bmAtPNZwwFCHYOCNx5TC5QbOn?= =?us-ascii?Q?Ixmrgn2OIg2UADeQGVndsvgvonfbVn1+7swqzL4LIEXvL15RRAgdvRtvNHHH?= =?us-ascii?Q?Xi1dFlYJseVR5M1LHfppPBlcSNMVEatD26Dq1gzLFEhhHVTYg3zXgEILvYK6?= =?us-ascii?Q?UqjR97/+n/4VyTwtOF/0YTefXfP9ooJmg9o9hPTobw0y2L3PGymkfmqxPs6I?= =?us-ascii?Q?9PXQO9F+ewYYARNYkwYENx39zXrgJbt6dCOfewova9tOji1nMiDTdD8EZlAW?= =?us-ascii?Q?zbC40BM3LubNjwJYHPn5Lw/7JJ9tUOPnwN2JyvkSpF8zTR9IQVK9z7weQNtE?= =?us-ascii?Q?rkZ1pkkMRPRKbTGfCKVMThSQ5rdt8hSJ4d/D7jEHtX04cgmBfNcw1ELcVJ/u?= =?us-ascii?Q?1+6I5vlDwFg8Sl1kUoDH7KsO?= X-OriginatorOrg: oracle.com X-MS-Exchange-CrossTenant-Network-Message-Id: bd81fe17-3352-4d50-8914-08d958b53bef X-MS-Exchange-CrossTenant-AuthSource: MWHPR1001MB2365.namprd10.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 06 Aug 2021 08:36:07.0682 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 4e2c6054-71cb-48f1-bd6c-3a9705aca71b X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: GrU3wSzQt3NFl/62XeQwV4n4lBcpbKLevTJvCrtP9ZeUbjfvqfKUACvbZZKqD1nMG/Zs6uzrlqc3NPo0dAnjOVtP51WZoQFB83ez4QvyKQw= X-MS-Exchange-Transport-CrossTenantHeadersStamped: MWHPR1001MB2205 X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=10067 signatures=668682 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxscore=0 malwarescore=0 phishscore=0 spamscore=0 adultscore=0 suspectscore=0 mlxlogscore=999 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2107140000 definitions=main-2108060060 X-Proofpoint-GUID: ZUM-4A5gHgNzpA10BD2WH8M52QFBASTM X-Proofpoint-ORIG-GUID: ZUM-4A5gHgNzpA10BD2WH8M52QFBASTM Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Wed, Aug 04, 2021 at 04:23:26PM +0200, Joerg Roedel wrote: > On Wed, Aug 04, 2021 at 03:58:34PM +0300, Dan Carpenter wrote: > > exc_page_fault() <-- called with preempt disabled > > --> kvm_handle_async_pf() > > --> __kvm_handle_async_pf() > > --> kvm_async_pf_task_wait_schedule() calls schedule(). > > This call path can not be taken in the page-fault handler when called > from the #VC handler. To take this path the host needs to inject an > async page-fault, especially setting async pf flags, without injecting a > page-fault exception on its own ... and when the #VC handler is running. > KVM is not doing that. > > Okay, the hypervisor can be malicious, but otherwise this can't happen. > To mitigate a malicious hypervisor threat here it might be a solution to > not call the page-fault handler directly from the #VC handler and let it > re-fault after the #VC handler returned. > Thanks for taking a look at this. Also it turns out that my check wasn't taking in_atomic() into consideration either so I've added that. regards, dan carpenter