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Peter Anvin" , Peter Zijlstra , Thomas Gleixner , Josh Poimboeuf , Nick Desaulniers Subject: Re: [PATCH v2 -tip] x86/percpu: Use C for arch_raw_cpu_ptr() Thread-Topic: [PATCH v2 -tip] x86/percpu: Use C for arch_raw_cpu_ptr() Thread-Index: AQHZ+5jZGZywpkB5zE2yxvhqDFo/FrBDSECAgAAOE4CAAAQxgIABoxnfgAAgI4CAAAYlgIAHqOMRgAAI04CAADzyiIABTsvzgAADAQCAAB/hAIAADVOAgAADqIA= Date: Tue, 17 Oct 2023 22:06:51 +0000 Message-ID: <10930088-3B4E-4BED-896C-CA66AB196010@vmware.com> References: <20231010164234.140750-1-ubizjak@gmail.com> <0617BB2F-D08F-410F-A6EE-4135BB03863C@vmware.com> <7D77A452-E61E-4B8B-B49C-949E1C8E257C@vmware.com> <9F926586-20D9-4979-AB7A-71124BBAABD3@vmware.com> In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-mailer: Apple Mail (2.3731.700.6) authentication-results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=vmware.com; x-ms-publictraffictype: Email x-ms-traffictypediagnostic: BY3PR05MB8531:EE_|SA3PR05MB9761:EE_ x-ms-office365-filtering-correlation-id: 91da9525-4d2a-473a-fedf-08dbcf5d5da9 x-ms-exchange-senderadcheck: 1 x-ms-exchange-antispam-relay: 0 x-microsoft-antispam: BCL:0; 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charset="us-ascii" Content-ID: <1538DFED908F2E4699C3350A031E93D6@namprd05.prod.outlook.com> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: vmware.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: BY3PR05MB8531.namprd05.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 91da9525-4d2a-473a-fedf-08dbcf5d5da9 X-MS-Exchange-CrossTenant-originalarrivaltime: 17 Oct 2023 22:06:51.2810 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: b39138ca-3cee-4b4a-a4d6-cd83d9dd62f0 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: oWYg4UthisK5ysStkifSZ15nN13PvAXhtTPGxCfdpMNQDvVdUXHCK7evdA2QT7olUH6AxZF1PZc4njqsfFkODg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA3PR05MB9761 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On Oct 18, 2023, at 12:53 AM, Linus Torvalds wrote: >=20 >=20 > but none of this should even matter, because by the time we actually > *schedule* that thread, we'll set active_mm to the right thing. >=20 > Can anybody see what's up? Could it be related to exec_mmap() -> exec_mm_release() -> mm_release() -> = deactivate_mm() ? #define deactivate_mm(tsk, mm) \ do { \ if (!tsk->vfork_done) \ shstk_free(tsk); \ load_gs_index(0); \ loadsegment(fs, 0); \ } while (0) We change gs_index(), so perhaps it affects later GS reads. There is also t= his X86_BUG_NULL_SEG. Need to dive deeper; just initial thoughts though (i.e., = I might be completely off).