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charset="us-ascii" Content-ID: <9C1DD6E9B24AA642B97CF772D98C9AF6@namprd11.prod.outlook.com> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: PH0PR11MB4855.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 169c2b0d-edd6-432a-0006-08d8b6c17c2c X-MS-Exchange-CrossTenant-originalarrivaltime: 12 Jan 2021 06:15:39.9683 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 46c98d88-e344-4ed4-8496-4ed7712e255d X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: vXLSeNNxnkGRUBJADuO1VsxMCEf/OcrJwd00GsPVgG49ajpxGYGqdMPHN7NCq39/yhpTnrD10EItgFhT/hRF7ZpxaZOhu2WUWkPU8H4/jWo= X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH0PR11MB4917 X-OriginatorOrg: intel.com Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On Jan 11, 2021, at 13:06, Andy Lutomirski wrote: >=20 >> On Jan 11, 2021, at 12:00 PM, Borislav Petkov wrote: >>=20 >> Or do you mean I should add "unsafe_fsgsbase" to grub cmdline and bisect >> with fsgsbase enabled in all test kernels? >=20 > Yes. But I can also look myself in a bit. I was able to find this patch in that way: commit 0bf7e460361c703333f3a82e50e7871465fe20f9 Author: Andy Lutomirski Date: Thu May 28 16:13:51 2020 -0400 x86/process/64: Use FSBSBASE in switch_to() if available The GDB behavior looks to be different between the two cases -- with vs without gdb server, when I checked the GS/GSBASE values on the ptrace front= . It set the correct GSBASE (e.g.,=3D0xf7fcf0c0) of GS=3D0x63 without running= the server. But GSBASE=3D0 with the server. When I forced to set the correct ba= se, it exited normally. Thanks, Chang