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Content-Language: en-US To: Dexuan Cui , Jeremi Piotrowski Cc: Borislav Petkov , "sandipan.das@amd.com" , "Gupta, Pankaj" , "ray.huang@amd.com" , "brijesh.singh@amd.com" , "michael.roth@amd.com" , "kvm@vger.kernel.org" , "x86@kernel.org" , Tianyu Lan , "linux-hyperv@vger.kernel.org" , "linux-kernel@vger.kernel.org" References: <20230216091431.GA10166@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net> From: Tom Lendacky In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: BN0PR04CA0024.namprd04.prod.outlook.com (2603:10b6:408:ee::29) To DM4PR12MB5229.namprd12.prod.outlook.com (2603:10b6:5:398::12) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DM4PR12MB5229:EE_|CH3PR12MB8583:EE_ X-MS-Office365-Filtering-Correlation-Id: c160acbc-64bc-48e6-48b6-08db271269dd X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:DM4PR12MB5229.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230025)(4636009)(366004)(136003)(396003)(39860400002)(346002)(376002)(451199018)(38100700002)(6666004)(5660300002)(8676002)(66946007)(66476007)(4326008)(316002)(478600001)(45080400002)(83380400001)(110136005)(66556008)(54906003)(8936002)(31696002)(86362001)(41300700001)(2906002)(36756003)(6486002)(53546011)(2616005)(186003)(31686004)(26005)(6512007)(6506007)(43740500002)(45980500001);DIR:OUT;SFP:1101; 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The relevant part of the comment is this: >> "If we came here via startup_32(), cr3 will be _pgtable already". >> >> Booting a (non-SNP) guest via BIOS I end up in the first branch. Upstream SNP >> support requires OVMF (UEFI) so we'll always reach the kernel in 64-bit mode >> (startup_64?), and end up in the second branch. >> >> Jeremi > > Here I'm running a C-bit mode SNP guest on Hyper-V via "direct-boot" (i.e. > I run Set-VMFirmware to tell Hyper-V to boot the kernel directly without > UEFI). Looks like arch/x86/boot/compressed/head_64.S: startup_32 runs > first and calls startup_64 later (?) This might explain why I'm getting into > the first branch, which I hope could be fixed by someone... It sounds like there aren't enough pages available to satisfy the page split in order to make the GHCB shared. Have you tried changing BOOT_INIT_PGT_SIZE to increase it by 1 page. Splitting the page will require an additional page table, I think that is all that would be needed. Thanks, Tom