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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 References: <20210602140416.23573-1-brijesh.singh@amd.com> <20210602140416.23573-22-brijesh.singh@amd.com> From: Tom Lendacky Message-ID: <8a598020-7d89-b399-efb9-735b2a6da8a9@amd.com> Date: Fri, 11 Jun 2021 08:16:58 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [67.79.209.213] X-ClientProxiedBy: SA9PR13CA0086.namprd13.prod.outlook.com (2603:10b6:806:23::31) To DM5PR12MB1355.namprd12.prod.outlook.com (2603:10b6:3:6e::7) X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from office-linux.texastahm.com (67.79.209.213) by SA9PR13CA0086.namprd13.prod.outlook.com (2603:10b6:806:23::31) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4242.9 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?cHNqQ3EwN0dJbkRqTzc3ckY1VER4c3VXc08rL05nbS84Vy9qU1JENWtqZXhB?= =?utf-8?B?a2lJUmlaeHZmRlZNYURCemYrYW03MEp6ZDlWQ2N3TXQyOUhoNEFUTFQxM3hx?= =?utf-8?B?ZC81anIzS0V3ekNpajZpOVNPNGpiMnNEOTFlRHdhRW80VGJNUEM1Z1ppUExV?= =?utf-8?B?MW9tMU9TcWZXRGUwY2k4Tyt4aG5HbWxZRmlVWGhuVXc4aXNoRG43ODQ2OGhN?= =?utf-8?B?SGNzSmRxWjU2ZzBrS1BTN2NTYlZwTGkrYUYvN05RWEd0eGhLSjc0UHdCWDBM?= =?utf-8?B?OFQ2WjNmWTZyOGQxNm1vYjM3eGx2VlR6S29nOFdLdmM2YW1RcnlyS3ZzL2JB?= =?utf-8?B?OWVGd3BXSWFMNmNYS2ordktucEIrSzhLZlhibEU4Y3Q1OXdtTHNCTldhUEZS?= =?utf-8?B?Qy9KeFBrcG1HTmNqVWd3a1RMTTg4TmNnOFp5M1hZOSt6M1UrODgwc1QzTjZQ?= =?utf-8?B?TVFjZkE3Q2tzNVc3cTlXU1FtSS84L2ZNR2dYcDhYT3I2eEF5M2gzTTBaUVBj?= =?utf-8?B?QU5pNUcwVGJVa2dVTU5KZnJRd3NMc2xza1N0QXhidzZjTnBLdlQrb0ZpK1Ns?= =?utf-8?B?STRQTkNKOXlCSmE1dFUrVEIxb1lNT2xhNzUyeFlRL1ptQ1pOSUdrcTV0WU5H?= =?utf-8?B?RXNBTjRnOWxYS3FRdkNoSEhsdXJaVlhBT1hmbGdyMVRRcVFsMXBqa0VML2Z6?= =?utf-8?B?blQwME1rbWw1NkFBbEcyWDJNWDNpWkJHQ2gxclFKSkc3dnlXaUIyeEswMFRi?= =?utf-8?B?a0x0eFRud0swL3duZjVEQW9zb00xM05jYTYrVk5xaW1rV0NOTjR3c1dZR2lH?= =?utf-8?B?VTR3UU00Tk5OenE3NTYxRUczRE04U2JGS3BLaEJzYnlIR2tPdjd4RE1mK1NY?= =?utf-8?B?aEhnN0lSamwzSlJ3RjJIaXNoRWRkQWQzc2d5TDQrTVVnQmx5TENYbWlCOUxF?= =?utf-8?B?Z1RVdmtYQnMwSjM2Ulk3UlFKcVV4QmJhVU05azVGclNvejllN1dwZ0pwWmFO?= =?utf-8?B?WktRRjZQaDkwSUQ5N2Q0VXhRUWdkVkVMbWFObXltQkt1VFhEQnRDOTN2UDkx?= =?utf-8?B?VDV5N0FjTHJOVU1IQ0swR0N1VkJmbVRSbHpIQzRSR2FEYUlYN2NMQThuQkR6?= =?utf-8?B?U2JYdDg4T2FWaHkyWFM5UkorMDhPZTV1TU94aFpQWTc2MUZzMnhYbjE5TW13?= =?utf-8?B?T1pCSmhGNDkzWkVaZmtkam1mTVgrR2R0ZUxVQWFTcms4S3hlR1dFZHhMeEo2?= =?utf-8?B?UFQzKzI2L0ZMZ0pNUzhzWTFDMUxCMCtNMnpKMnh6R3lsKzNYTVpreEtpWTc0?= =?utf-8?B?aCtkZW1KYnhzU0IvbzREZDRQZ0ZjRW1RQkNGQXdLVFBSbVJYRUdxSjBHVmRj?= =?utf-8?B?bERFSkhBVWNwWHVkUVF3QjVmL1ZpdU9hem5VYzRQRi82Njg4dGlmNm55d1RK?= =?utf-8?B?YlUrdEphcFlYTzlmUDRWd1FGQjhuVWlGYXRMZUVwWkIvTStxU3pHSXNxeXQx?= =?utf-8?B?a3cwdkRkaHp5V3N3WnJ0VFR2aFFzU1JuQ3JWRFY1SFJlNDB3NWV1OWtUa1Vh?= =?utf-8?B?bW9HWlErWVdRWjhLc25vdXVkS3MrSWtuRmhzUGlGb2xPekU2RUJTc09KQmlY?= =?utf-8?B?cW9OS3c0SzVMWXhyMHFleTV0YmhPcmM5SHg2ZHdRazlDMS9iQi9IektSS0JX?= =?utf-8?B?RzN5d3lZdEdqQ0Q3Q2pBdkJqVmtlMWJVWXpjY0NtckFFcVcvdndQSWVDWDIz?= =?utf-8?Q?eyySo5SoVhfSJIL6hbNxjcyJyzL94+h7SXjaZTg?= X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-Network-Message-Id: d8d56218-0169-479b-ae2b-08d92cdb336c X-MS-Exchange-CrossTenant-AuthSource: DM5PR12MB1355.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 11 Jun 2021 13:17:02.4884 (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: jTI5x4BpuNoL1aQc5KsELr2L0jFSF4BEwHM1ZV6cHuC68AqpkHu/1Dirb5+tGL1muBIygQ5ypm/A8yHUfYPCPA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM5PR1201MB0121 On 6/9/21 2:24 PM, Dr. David Alan Gilbert wrote: > * Brijesh Singh (brijesh.singh@amd.com) wrote: >> Version 2 of GHCB specification provides NAEs that can be used by the SNP >> guest to communicate with the PSP without risk from a malicious hypervisor >> who wishes to read, alter, drop or replay the messages sent. >> >> The hypervisor uses the SNP_GUEST_REQUEST command interface provided by >> the SEV-SNP firmware to forward the guest messages to the PSP. >> >> In order to communicate with the PSP, the guest need to locate the secrets >> page inserted by the hypervisor during the SEV-SNP guest launch. The >> secrets page contains the communication keys used to send and receive the >> encrypted messages between the guest and the PSP. >> >> The secrets page is located either through the setup_data cc_blob_address >> or EFI configuration table. >> >> Create a platform device that the SNP guest driver can bind to get the >> platform resources. The SNP guest driver can provide userspace interface >> to get the attestation report, key derivation etc. >> >> The helper snp_issue_guest_request() will be used by the drivers to >> send the guest message request to the hypervisor. The guest message header >> contains a message count. The message count is used in the IV. The >> firmware increments the message count by 1, and expects that next message >> will be using the incremented count. >> >> The helper snp_msg_seqno() will be used by driver to get and message >> sequence counter, and it will be automatically incremented by the >> snp_issue_guest_request(). The incremented value is be saved in the >> secrets page so that the kexec'ed kernel knows from where to begin. >> >> See SEV-SNP and GHCB spec for more details. >> >> Signed-off-by: Brijesh Singh >> --- >> arch/x86/include/asm/sev.h | 12 +++ >> arch/x86/include/uapi/asm/svm.h | 2 + >> arch/x86/kernel/sev.c | 176 ++++++++++++++++++++++++++++++++ >> arch/x86/platform/efi/efi.c | 2 + >> include/linux/efi.h | 1 + >> include/linux/sev-guest.h | 76 ++++++++++++++ >> 6 files changed, 269 insertions(+) >> create mode 100644 include/linux/sev-guest.h >> >> +u64 snp_msg_seqno(void) >> +{ >> + struct snp_secrets_page_layout *layout; >> + u64 count; >> + >> + layout = snp_map_secrets_page(); >> + if (layout == NULL) >> + return 0; >> + >> + /* Read the current message sequence counter from secrets pages */ >> + count = readl(&layout->os_area.msg_seqno_0); > > Why is this seqno_0 - is that because it's the count of talking to the > PSP? Yes, the sequence number is an ever increasing value that is used in communicating with the PSP. The PSP maintains the next expected sequence number and will reject messages which have a sequence number that is not in sync with the PSP. The 0 refers to the VMPL level. Each VMPL level has its own sequence number. > >> + iounmap(layout); >> + >> + /* >> + * The message sequence counter for the SNP guest request is a 64-bit value >> + * but the version 2 of GHCB specification defines the 32-bit storage for the >> + * it. >> + */ >> + if ((count + 1) >= INT_MAX) >> + return 0; > > Is that UINT_MAX? > >> + >> + return count + 1; >> +} >> +EXPORT_SYMBOL_GPL(snp_msg_seqno); >> + >> +static void snp_gen_msg_seqno(void) >> +{ >> + struct snp_secrets_page_layout *layout; >> + u64 count; >> + >> + layout = snp_map_secrets_page(); >> + if (layout == NULL) >> + return; >> + >> + /* Increment the sequence counter by 2 and save in secrets page. */ >> + count = readl(&layout->os_area.msg_seqno_0); >> + count += 2; > > Why 2 not 1 ? The return message by the PSP also increments the sequence number, hence the increment by 2 instead of 1 for the next message to be submitted. I'll let Brijesh address the other questions. Thanks, Tom