From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0B998C67863 for ; Tue, 23 Oct 2018 18:43:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D1C6B20665 for ; Tue, 23 Oct 2018 18:43:27 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D1C6B20665 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728859AbeJXDIA (ORCPT ); Tue, 23 Oct 2018 23:08:00 -0400 Received: from mga05.intel.com ([192.55.52.43]:55078 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727758AbeJXDH7 (ORCPT ); Tue, 23 Oct 2018 23:07:59 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga004.jf.intel.com ([10.7.209.38]) by fmsmga105.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 23 Oct 2018 11:43:24 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.54,417,1534834800"; d="scan'208";a="243726561" Received: from chang-linux-2.sc.intel.com ([10.3.52.139]) by orsmga004.jf.intel.com with ESMTP; 23 Oct 2018 11:43:23 -0700 From: "Chang S. Bae" To: Ingo Molnar , Thomas Gleixner , Andy Lutomirski , "H . Peter Anvin" Cc: Andi Kleen , Dave Hansen , Markus T Metzger , Ravi Shankar , "Chang S . Bae" , LKML Subject: [v3 00/12] x86: Enable FSGSBASE instructions Date: Tue, 23 Oct 2018 11:42:22 -0700 Message-Id: <20181023184234.14025-1-chang.seok.bae@intel.com> X-Mailer: git-send-email 2.19.1 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org FSGSBASE is a 64-bit instruction set to allow read/write FS/GSBASE from any privileges. Since introduced in Ivybridge, enabling efforts has been revolving in a quite long period of time, for various reasons [2,3,4]. After the extended discussions [1], the new ABIs are finally introduced to customize FS/GSBASE separately from the selector. Benefits: Some performance benefit in context switch is expected by skipping MSR write for GSBASE. User-level programs (such as JAVA-based) may benefit from avoiding system calls to edit FS/GSBASE. Major changes in the kernel: * In a context switch, a thread's FS/GSBASE will be secured regardless of its selector, base on the discussion [1]. * (Subsequently) ptracer should expect a divergence of FS/GS index and base values. There was a controversial debate on the concerns for a backward compatibility (mostly for GDB. [7,8]). We finally concluded it is insignificant in real usages. * On the paranoid_entry, GSBASE is updated to point the per_CPU base and the original GSBASE is restored at the exit. Virtualization: A FSGSBASE-enabled VM can be located on a host either with HW virtualization or with SW emulation. KVM advertises FSGSBASE when physical CPU has. The emulation is supported in QEMU/TCG [5]. In a pool of the mixed systems, VMM may disable FSGSBASE for seamless VM migrations [6]. Update from v2 [10]: * Separate out the preparatory patches [11] (now merged to the tip) * Bisect the paranoid_entry update patch * Edit minor nits Updates from v1 [9]: * Update the GSBASE update mechanism on the paranoid entry/exit. * Exclude ptracer backward compatibility patches. * Include FSGSBASE documentation and enumerating capability for user space * Add the TAINT_INSECURE flag. [1] Recent discussion on LKML: https://marc.info/?t=150147053700001&r=1&w=2 [2] Andy Lutomirski’s patchwork work : https://git.kernel.org/pub/scm/linux/kernel/git/luto/linux.git/log/?h=x86/fsgsbase [3] Patchset shown in 2016: https://lore.kernel.org/patchwork/patch/660520 [4] Patchset shown in 2014: https://lore.kernel.org/patchwork/patch/460288 [5] QEMU with FSGSBASE emulation: https://github.com/qemu/qemu/blob/026aaf47c02b79036feb830206cfebb2a726510d/target/i386/translate.c#L8186 [6] 5-level EPT: http://lkml.kernel.org/r/9ddf602b-6c8b-8c1e-ab46-07ed12366593@redhat.com [7] RR/FSGSBASE: https://mail.mozilla.org/pipermail/rr-dev/2018-March/000616.html [8] CRIU/FSGSBASE: https://lists.openvz.org/pipermail/criu/2018-March/040654.html [9] Version 1: https://lore.kernel.org/patchwork/cover/934843 [10] Version 2: https://lore.kernel.org/patchwork/cover/912063 [11] x86: infra to enable FSGSBASE https://lore.kernel.org/patchwork/cover/988180 Andi Kleen (3): x86/fsgsbase/64: Add intrinsics/macros for FSGSBASE instructions x86/elf: Enumerate kernel FSGSBASE capability in AT_HWCAP2 x86/fsgsbase/64: Add documentation for FSGSBASE Andy Lutomirski (4): x86/fsgsbase/64: Add 'unsafe_fsgsbase' to enable CR4.FSGSBASE x86/fsgsbase/64: Preserve FS/GS state in __switch_to() if FSGSBASE is on selftests/x86/fsgsbase: Test WRGSBASE x86/fsgsbase/64: Enable FSGSBASE by default and add a chicken bit Chang S. Bae (5): taint: Introduce a new taint flag (insecure) x86/fsgsbase/64: Enable FSGSBASE instructions in the helper functions x86/fsgsbase/64: When copying a thread, use the FSGSBASE instructions if available x86/fsgsbase/64: Introduce the new FIND_PERCPU_BASE macro x86/fsgsbase/64: Use the per-CPU base as GSBASE at the paranoid_entry .../admin-guide/kernel-parameters.txt | 2 + Documentation/sysctl/kernel.txt | 1 + Documentation/x86/fsgs.txt | 104 +++++++++++++ arch/x86/entry/entry_64.S | 73 +++++++-- arch/x86/include/asm/fsgsbase.h | 140 +++++++++++++++++- arch/x86/include/asm/inst.h | 15 ++ arch/x86/include/uapi/asm/hwcap2.h | 3 + arch/x86/kernel/cpu/common.c | 22 +++ arch/x86/kernel/process_64.c | 128 +++++++++++++--- include/linux/kernel.h | 3 +- kernel/panic.c | 1 + tools/testing/selftests/x86/fsgsbase.c | 110 +++++++++++++- 12 files changed, 556 insertions(+), 46 deletions(-) create mode 100644 Documentation/x86/fsgs.txt -- 2.19.1