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Peter Anvin" , Thomas Gleixner , Borislav Petkov , Dave Hansen , Andy Lutomirski , Kees Cook , Dave Hansen , Masami Hiramatsu Subject: Re: [PATCH v3 6/7] x86/alternatives: use temporary mm for text poking Thread-Topic: [PATCH v3 6/7] x86/alternatives: use temporary mm for text poking Thread-Index: AQHUcwQ5CMopNGTk70+f2dIwnm2sU6VBMXWAgABMjQA= Date: Mon, 5 Nov 2018 18:04:42 +0000 Message-ID: References: <20181102232946.98461-1-namit@vmware.com> <20181102232946.98461-7-namit@vmware.com> <20181105133041.GC22467@hirez.programming.kicks-ass.net> In-Reply-To: <20181105133041.GC22467@hirez.programming.kicks-ass.net> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: spf=none (sender IP is ) smtp.mailfrom=namit@vmware.com; x-originating-ip: [208.91.2.1] x-ms-publictraffictype: Email x-microsoft-exchange-diagnostics: 1;BYAPR05MB5848;20:H5tK3DtZZiQLKsULxMwRmqGtJHDvD7MuuKmRtu2Qad/QHAEHiK4tF1ezJkPE+8Rhtpczj4iVeN/1B6qheH/P2qBFs0np7ponUUh+JU4KCWVPIBiO7eJ4GcAuIth5uhoHgrgFmeqQ6rXgorNxdODi4I+fmS/WTBW8c8eAKCyVHH4= x-ms-exchange-antispam-srfa-diagnostics: SOS; x-ms-office365-filtering-correlation-id: 3e11b123-9c96-4ae2-d8a7-08d64349298d x-microsoft-antispam: BCL:0;PCL:0;RULEID:(7020095)(4652040)(8989299)(4534185)(4627221)(201703031133081)(201702281549075)(8990200)(5600074)(711020)(2017052603328)(7153060)(7193020);SRVR:BYAPR05MB5848; x-ms-traffictypediagnostic: BYAPR05MB5848: x-microsoft-antispam-prvs: x-exchange-antispam-report-test: UriScan:(9452136761055)(61668805478150)(228905959029699); x-ms-exchange-senderadcheck: 1 x-exchange-antispam-report-cfa-test: BCL:0;PCL:0;RULEID:(8211001083)(6040522)(2401047)(5005006)(8121501046)(93006095)(93001095)(10201501046)(3002001)(3231382)(944501410)(52105095)(148016)(149066)(150057)(6041310)(201703131423095)(201702281528075)(20161123555045)(201703061421075)(201703061406153)(20161123560045)(20161123564045)(20161123562045)(20161123558120)(201708071742011)(7699051)(76991095);SRVR:BYAPR05MB5848;BCL:0;PCL:0;RULEID:;SRVR:BYAPR05MB5848; x-forefront-prvs: 08476BC6EF x-forefront-antispam-report: SFV:NSPM;SFS:(10009020)(346002)(376002)(136003)(396003)(366004)(39860400002)(189003)(199004)(7736002)(53546011)(8676002)(36756003)(6436002)(8936002)(2906002)(97736004)(305945005)(6246003)(81166006)(316002)(81156014)(256004)(99286004)(14444005)(3846002)(76176011)(6486002)(6506007)(86362001)(6512007)(102836004)(26005)(7416002)(53936002)(6116002)(478600001)(83716004)(71190400001)(71200400001)(82746002)(476003)(486006)(2616005)(68736007)(446003)(5660300001)(6916009)(11346002)(54906003)(66066001)(14454004)(186003)(4326008)(33656002)(25786009)(229853002)(2900100001)(106356001)(105586002);DIR:OUT;SFP:1101;SCL:1;SRVR:BYAPR05MB5848;H:BYAPR05MB4776.namprd05.prod.outlook.com;FPR:;SPF:None;LANG:en;PTR:InfoNoRecords;MX:1;A:1; received-spf: None (protection.outlook.com: vmware.com does not designate permitted sender hosts) x-microsoft-antispam-message-info: IOhL5QhbQOvE6vgM2X4/WTcEOfBrCGjy8Gpq9T/wI1HYutaCHHodr/6Z5aGmvEly+8pRvdA+ruV76mpN2hysWaZnN1UEHDguWERIs5yCdC9egzYhv5Ymfn+FJobMaOs1TTeQNRIToEIfHm+qoMIk0osJ7fv50+sQT+RrMTmPhsUqnIZCNsNQJ5C03ap1EMzWj2k55Nf6unPgwS1EDndJaj5m9JC882LIplQ7NvDDM2uO26hPfMe0FaLcZmdYMKcEcsE0dNuhGeI0/8em4uRvexfXxZNpmBerqIs0pVxSWQfW+XR1b2LfEzOIrkDQyR3EQg04IrCGaTZSr7W5erLSRyap3b926XMQb5XghgfvXGI= spamdiagnosticoutput: 1:99 spamdiagnosticmetadata: NSPM Content-Type: text/plain; charset="us-ascii" Content-ID: <6AE980EF71EDCD45975C6490CD42D3E0@namprd05.prod.outlook.com> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: vmware.com X-MS-Exchange-CrossTenant-Network-Message-Id: 3e11b123-9c96-4ae2-d8a7-08d64349298d X-MS-Exchange-CrossTenant-originalarrivaltime: 05 Nov 2018 18:04:42.5407 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: b39138ca-3cee-4b4a-a4d6-cd83d9dd62f0 X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR05MB5848 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Peter Zijlstra Sent: November 5, 2018 at 1:30:41 PM GMT > To: Nadav Amit > Cc: Ingo Molnar , linux-kernel@vger.kernel.org, x86@ker= nel.org, H. Peter Anvin , Thomas Gleixner , Borislav Petkov , Dave Hansen , Andy Lutomirski , Kees Cook , D= ave Hansen , Masami Hiramatsu > Subject: Re: [PATCH v3 6/7] x86/alternatives: use temporary mm for text p= oking >=20 >=20 > On Fri, Nov 02, 2018 at 04:29:45PM -0700, Nadav Amit wrote: >> + unuse_temporary_mm(prev); >> + >> + pte_unmap_unlock(ptep, ptl); >=20 > That; that does kunmap_atomic() on 32bit. >=20 > I've been thinking that the whole kmap_atomic thing on x86_32 is > terminally broken, and with that most of x86_32 is. >=20 > kmap_atomic does the per-cpu fixmap pte fun-and-games we're here saying > is broken. Yes, only the one CPU will (explicitly) use those fixmap PTEs > and thus the local invalidate _should_ work. However nothing prohibits > speculation on another CPU from using our fixmap addresses. Which can > lead to the remote CPU populating its TLBs for our fixmap entry. >=20 > And, as we've found, there are AMD parts that #MC when there are > mis-matched TLB entries. >=20 > So what do we do? mark x86_32 SMP broken? pte_unmap() seems to only use kunmap_atomic() when CONFIG_HIGHPTE is set, n= o? Do most distributions run with CONFIG_HIGHPTE?