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Wed, 25 Sep 2024 16:12:51 -0500 Message-ID: <1258d32d-ee54-4a5d-bc92-6c1f8179235a@amd.com> Date: Wed, 25 Sep 2024 17:12:51 -0400 Precedence: bulk X-Mailing-List: linux-kbuild@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 01/28] x86/pvh: Call C code via the kernel virtual mapping To: Ard Biesheuvel , CC: Ard Biesheuvel , , "H. Peter Anvin" , Andy Lutomirski , Peter Zijlstra , Uros Bizjak , Dennis Zhou , Tejun Heo , Christoph Lameter , Mathieu Desnoyers , "Paolo Bonzini" , Vitaly Kuznetsov , Juergen Gross , Boris Ostrovsky , Greg Kroah-Hartman , Arnd Bergmann , Masahiro Yamada , Kees Cook , Nathan Chancellor , Keith Packard , Justin Stitt , Josh Poimboeuf , "Arnaldo Carvalho de Melo" , Namhyung Kim , "Jiri Olsa" , Ian Rogers , Adrian Hunter , Kan Liang , , , , , , , , , , , References: <20240925150059.3955569-30-ardb+git@google.com> <20240925150059.3955569-31-ardb+git@google.com> Content-Language: en-US From: Jason Andryuk In-Reply-To: <20240925150059.3955569-31-ardb+git@google.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: None (SATLEXMB05.amd.com: jason.andryuk@amd.com does not designate permitted sender hosts) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BN2PEPF000055DC:EE_|LV8PR12MB9360:EE_ X-MS-Office365-Filtering-Correlation-Id: f2ea1ed0-686e-47fc-1992-08dcdda6d310 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|7416014|36860700013|1800799024|82310400026; X-Microsoft-Antispam-Message-Info: =?utf-8?B?MHh0aS9xdXBOWkNYSmRtcUEvWUYyanpaQi9sTFNreTBnMmJFUC8yRld0SnlN?= =?utf-8?B?RUVrekREVWR3cllESzZHZTVnM21qZVlGWER1dTdTZEt6d1JUU2ZBQ1JxcWE4?= =?utf-8?B?aW5XbDJzM3NZRUN6anRYR2xIZkI4R29QSXdmTmRKb0U4ZGRpS0NqZVd5Ny9T?= =?utf-8?B?dnZxaVI5dmFaeXRORmc1YzhncWllZDZJcWNpQmpPSkc3aGUzeVV1UnBoemxE?= =?utf-8?B?RTNaSjNESStZV011TE1aRTluUjNjMHNzeWlOdG12VXF2dUJEUS9KUEFHM2Ex?= =?utf-8?B?WkJ5M2pud1RsdGE5UXVXRndXK2NyT1I3U0xJR016VHRCWkU0cmM0OVdhTVJO?= =?utf-8?B?U1hIRWtSMFZ4R29MbTlOT2c2aXZqWDk1V2hUTkNuZlBSMVVsTFZWemo4c3dx?= =?utf-8?B?VFV2SWJlRnBJWUY5aFJtMzJmZDVISVJwUlBEaTE1TDlEb0dwdEdpeDZ2b3Rq?= =?utf-8?B?aDdzeU5CTWYxYytEWGVFNkx5SlRDN3BHOE9wV2VHZ3lOTENtOVAyQ0FTNWgr?= =?utf-8?B?ekVxMjZ0TllDOVBTaHRjTFE3V3VlSHJyWVRDSkI5R1A5elBESm8rZGFsWkE3?= =?utf-8?B?SG5IWmFJZ1dJVXlNMStvVnFKZnA0alVxVitHOWhhOWVFL3Y4M1BsSkV3UW1k?= =?utf-8?B?QWxRNWdZZjhIbE1yTzE5ZGFTNy9EcjZOS083cWVmTllSV09yWUZWZTZvWEYy?= =?utf-8?B?WTZibGFiMXNrQVY0UTA4SGhRVDlqemV4SjlNd2JSYnNMdHo0VnRlczhNd3ZE?= =?utf-8?B?Tlh1b3htTTg1d2JtMDhVejRDYWJnbThTUHRycEFCWlJmb2drcS9YbGtQL0c3?= =?utf-8?B?MldyTHVYMUZwQ0FBaGw4TlYrL0dDQVhSdnVwYVBIUHltYXhSUnFvem1EQ055?= =?utf-8?B?bG04RlBiaXMwNGMzR1lrRURPK2UwYjV4ZHZIVXMrenBtS29rR094Qk5sS2Vl?= =?utf-8?B?eWlWLzQxZHlFcnlVY3gyRXZNSGVSODlwSzF4alM1eFRWeFBrOUJBOXc1QTBB?= =?utf-8?B?MEs1SWQwc1NjRmFuSHFRa0ZiVkpnVDJiRVBwRlNrTDl1bVcyRFpaT3U5b3pm?= =?utf-8?B?SzR4ZTl5WFRmZngrRUFxRHdwQkExK1AxaG9sNkQ2L0NJNGJ5NXhkSzNSNGR4?= =?utf-8?B?d1dkNVd0NjQ1eTVlTWE0dHkveDRBZi9LQmR6dkpTZU1JNjAzOXNjR3dpT0NI?= =?utf-8?B?b05Pcmw5ZXVWaGdPcWpzV1NONXN6bzROekF0UnVxbEFSTmRrZFowK2U5QSts?= =?utf-8?B?ZVlUR2R4SEJGUVgyODg1WlN3U0ltSnNFVWZWcnY2OXcyODhweWlsc3cwVFFw?= =?utf-8?B?K1RlZ3hrUzRST2VnUDJoMTYxT0VCODlTN0dwenFMV0V3R21ndzBNOU5ZNEh5?= =?utf-8?B?YjlyaHIvTXZraXo0S3o0WStzd3VyeElsRGJiVExkU1Jyc3REK29Va25aUVhy?= =?utf-8?B?UTVpYjhkQkRJTy9hNnA4SHQzSlFzSkwrd21SUndaVVJNNmFjVWhRR2tNb0FT?= =?utf-8?B?a2FzWnRXT1BvbUVtUkljVGxXMlJVd0pkTWtITFZKMXFCdHJFWE5lcGE4ZGtG?= =?utf-8?B?QTAvWTRrVjNCVTY1bFFtcE1ialpvRCsvVUNPTG4yQTc1T1BKRXNqeWNJTEZI?= =?utf-8?B?QkswK0VGWEh1cUk3WGFKTmJ0eG5jWFNQbFk2R1NlUXFDOEJueW9YT2lmUVht?= =?utf-8?B?NHNIYlJtTjZUcndCMnJ6NVpjb283b1RpTXJkcU5yNGw5TE53SnJjbjNXSnVX?= =?utf-8?B?Y1lYdlpacVFEdE9DSmxSam53d3dzYWpOK2didlptL0p2YTF3V3ZwQlg0MmJD?= =?utf-8?Q?mAG5gbbmFUCO6ntA+6BmX721jACkTf9uoy1CE=3D?= X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:CAL;SFV:NSPM;H:SATLEXMB04.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230040)(376014)(7416014)(36860700013)(1800799024)(82310400026);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 25 Sep 2024 21:12:55.4187 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: f2ea1ed0-686e-47fc-1992-08dcdda6d310 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[SATLEXMB04.amd.com] X-MS-Exchange-CrossTenant-AuthSource: BN2PEPF000055DC.namprd21.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: LV8PR12MB9360 On 2024-09-25 11:01, Ard Biesheuvel wrote: > From: Ard Biesheuvel > > Calling C code via a different mapping than it was linked at is > problematic, because the compiler assumes that RIP-relative and absolute > symbol references are interchangeable. GCC in particular may use > RIP-relative per-CPU variable references even when not using -fpic. > > So call xen_prepare_pvh() via its kernel virtual mapping on x86_64, so > that those RIP-relative references produce the correct values. This > matches the pre-existing behavior for i386, which also invokes > xen_prepare_pvh() via the kernel virtual mapping before invoking > startup_32 with paging disabled again. > > Fixes: 7243b93345f7 ("xen/pvh: Bootstrap PVH guest") > Signed-off-by: Ard Biesheuvel Tested-by: Jason Andryuk Reviewed-by: Jason Andryuk I found that before this change xen_prepare_pvh() would call through some pv_ops function pointers into the kernel virtual mapping. Regards, Jason