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Peter Anvin" , Ard Biesheuvel , Paolo Bonzini , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Andy Lutomirski , Dave Hansen , Sergio Lopez , Peter Gonda , Peter Zijlstra , Srinivas Pandruvada , David Rientjes , tony.luck@intel.com, npmccallum@redhat.com, Dov Murik Subject: Re: [PATCH Part1 RFC v3 22/22] virt: Add SEV-SNP guest driver To: Borislav Petkov References: <20210602140416.23573-1-brijesh.singh@amd.com> <20210602140416.23573-23-brijesh.singh@amd.com> <46499161-0106-3ae9-9688-0afd9076b28b@amd.com> <5b4d20db-3013-4411-03b9-708dd18dbe64@amd.com> From: Brijesh Singh Message-ID: <9c5037b6-d9a7-78e3-f2e4-bf8bebc12da7@amd.com> Date: Mon, 5 Jul 2021 05:39:04 -0500 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Content-Language: en-US X-Originating-IP: [70.112.153.56] X-ClientProxiedBy: SN4PR0401CA0007.namprd04.prod.outlook.com (2603:10b6:803:21::17) To BYAPR12MB2711.namprd12.prod.outlook.com (2603:10b6:a03:63::10) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from Brijeshs-MacBook-Pro.local (70.112.153.56) by SN4PR0401CA0007.namprd04.prod.outlook.com (2603:10b6:803:21::17) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4287.21 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?OG5uVmM1QU9HSHFEYWEyODlscm1DK3dFaW1rUHdSZjl5Zy94d1pDTHMwMlhS?= =?utf-8?B?WWgwblhGRmoyOFpMek45cFhVUERHS1BqOFFjUTdLQUJWQjZqZGN4MTZGUFlw?= =?utf-8?B?WkcwZlMxL01ZWHRxc0xsNHZvNUhqS0ZwR1JaNGdSM092bGNzSFpBSFh4bDkz?= =?utf-8?B?anE2YWZLVTY1Mk92Z3ZLS3lMM0tzOTJGWENZSk9reTIyZzBpN2VrTnpPaDRO?= =?utf-8?B?ZzZCVTU3dkJvZml4cHlUWGd2STQvS0ZPblJ4QytRT0o3K2VXU1orN1U5OGox?= =?utf-8?B?dlY1STBpQjZ1N2k1OFN0TDhiZ0VEelBVY2tIR01ZZTJ3dE1sTEtlQU0xWE9B?= =?utf-8?B?UTRhSjZwMVdpQURaTFhMQ2V6MDh3R0x1RFJaWWJ6WVVjZlF4c3hESnRoS1NW?= =?utf-8?B?TnFJMnMyWGthaFphdlBJSnNLNCtFWTZxaGlyQ1ltbkZYQ2NRbmNTcXlxRk9H?= =?utf-8?B?NWFkdURTazdPd2xRYUZXajZIWFBEZHRYK1JNam1ydTVWZ0IwamJLb0hpYzdB?= =?utf-8?B?bnJoMnRaRHUvWmFVNDhvNmU3V0p5S3FkL2tZak9mYm54RW9ONUVHWnRzR1Fa?= =?utf-8?B?a2dybzhpclRIMmZRQ2tJazhZVWszWlRtTmlMWGx5OFhLOFdQamxxQ1VuTUZG?= =?utf-8?B?RmR3ZjliQWlJTklvMTRWeDF0eUxVT2FNU1NEb0tYMVF2NkVjZDloOWdNYlk0?= =?utf-8?B?QkEyVWtnaGdNdy9mRDJQUWZST3BVQndPQnl3cC9nalA1a3h0V3RTWS9meTJz?= =?utf-8?B?UzhOVnJ3U0VuYWhrZnVCbU5JSWx4NkRBdzM4MkIzcVc2VEREOFNibDAzb1dW?= =?utf-8?B?ME1IWTVSZ0dyWTJIdTJoa25NRVVTNjhZQlA3am5qTWtKRFI4N2ZGVmtvcE96?= =?utf-8?B?TVhPdVRYNVpNL3hxalg1d21GYWtGWmZOU2NiQ3hhZEgvOTNtMHkvb0kxT1Vn?= =?utf-8?B?MVhFSkJpdnF6cklTSzJzRGk0TnF2c2ZZMEI3SW5aVEtlRU9vVzAwK1BETGox?= =?utf-8?B?QWNydzFIbkV5NGovZmpXYjQyVmhrYWowSHdDQkxPa3NKREdSYUJIZS94cE9j?= =?utf-8?B?bTZTNFBBRkt5alg3NVpnU2hUcC9nMTZTK0xTamNjdUFBQnAzMTZYcGI4b1c5?= =?utf-8?B?ZE5KTDBFZzh4dExsU3NVdXl3eHhqaUovNmZGWmxmdVlOZDlOKzVBQWtJT20w?= =?utf-8?B?cDlPc0NRVnVmM3E0TytCTjJDcnJ0NjBUOGhteVQwTEMzS1hBMlJIZi80WmNV?= =?utf-8?B?SmpHZEJ5U05mRjgwWTI5Ky85bHFLeEZQRGlBYkhtcVFxenkwSUhUZU5kamN1?= =?utf-8?B?ZkhVZEd0V2VWNU9rd25BbnNNMWdsME4vV25Rc09UZ0tEREpQZ3lYOTIzREVD?= =?utf-8?B?QTIyVUxLdE55b2hXYmpOY0pjb3J2SGZtSjF0dTNkWDVwcWhVd2grRnllTVJi?= =?utf-8?B?ZXduenBBdnNyZng5UHg4NTdrNkZYSWYzc2xMSm1taFNVN0tzY2Nvd25WNGQ3?= =?utf-8?B?RllycWUrVjN1Q1ZxZUs1cUhrSldyaTRZQVZtVUxINnNncUJjSFFaUXAvWXBr?= =?utf-8?B?Z0RTMHFyQTN0aWd0QVM2MFMxM3ZZS3Y1SmdRc05JdjhENi90SmNHS0V5SzE3?= =?utf-8?B?OFhmU1BXdWpsaFVMN3l4UkFQNTcyUmJoWGFJUjVYYStFYk1TdFVJZDFPUnB1?= =?utf-8?B?ZnhwaVBYTDUreGVoK3ZyZW8yYVJmSitjeGdyeko3L2JibTlubXEydkU1aGxr?= =?utf-8?Q?EV6oUfCtyx/oAZtSAr+lXtcOvS2PpKlM543CS+X?= X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-Network-Message-Id: 5b9313a0-b717-4254-80f7-08d93fa11e5e X-MS-Exchange-CrossTenant-AuthSource: BYAPR12MB2711.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 05 Jul 2021 10:39:08.4448 (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: BzJNYDKIJiQTcUbow747cQX49QR9ChnSSYw4gQ8tL7Km7iF/ynjKraxsRD5TqJO7Mmk3LXA9pVA3VaENt/QFRA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR12MB4728 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 7/3/21 11:19 AM, Borislav Petkov wrote: > On Thu, Jul 01, 2021 at 04:32:25PM -0500, Brijesh Singh wrote: >> The spec definition is present in include/linux/psp-sev.h but sometime >> we don't expose the spec defs as-is to userspace. > Why? > > Having such undocumented and maybe unwarranted differences - I still > don't see a clear reason why - is calling for additional and unnecessary > confusion. Because some of fields don't make any sense for the userspace interfaces.  > >> Several SEV/SEV-SNP does not need to be exposed to the userspace, >> those which need to be expose we provide a bit modified Linux uapi for >> it, and for SEV drivers we choose "_user" prefix. > Is that documented somewhere? > > Because "user" doesn't tell me it is a modified structure which is > different from the spec. We have good documentation for the SEV ioctl and structure provided through the KVM interface. Unfortunately the the documentation for the ioctl and structure provided through /dev/sev does not exist. We could look into adding this documentation outside this series. The structure provided through /dev/sev is identical to the structure documented in the spec with minor changes such as not exposing reserved fields or rename from paddr to uaddr etc. >> e.g >> a spec definition for the PEK import in include/linux/psp-sev.h is: >> struct sev_data_pek_cert_import { >> u64 pdh_cert_address; /* system physical address */ >> u32 pdh_cert_len; >> u32 reserved; >> ... >> }; >> >> But its corresponding userspace structure def in include/uapi/linux/psp-sev.h is: >> struct sev_user_data_pek_cert_import { >> __u64 pek_cert_uaddr; /* userspace address */ >> __u32 pek_cert_len; >> ... >> }; > And the difference is a single "u32 reserved"? Mostly yes. > > Dunno, from where I'm standing this looks like unnecessary confusion to > me. >> The ioctl handling takes care of mapping from uaddr to pa and other >> things as required. So, I took similar approach for the SEV-SNP guest >> ioctl. In this particular case the guest request structure defined in >> the spec contains multiple field but many of those fields are managed >> internally by the kernel (e.g seqno, IV, etc etc). > Ok, multiple fields sounds like you wanna save on the data that is > shovelled between kernel and user space and then some of the fields > don't mean a thing for the user API. Ok. > > But again, where is this documented and stated clear so that people are > aware? > > Or are you assuming that since the user counterparts are in > > include/uapi/linux/psp-sev.h > ^^^^ > > and it being an uapi header, then that should state that? > Yes, the assumption is user wanting to communicate to PSP through /dev/sev will need to include include psp-sev.h from uapi/linux/psp-sev.h. The header file itself document the fields definition, and then user need to refer to SEV SPEC for the further details. I could start documenting the SNP specific ioctl in Documentation/virt/coco/sevguest.rst and it can be later expanded to cover SEV and SEV-ES. -Brijesh