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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 43FD0C433FE for ; Tue, 4 Oct 2022 14:18:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229494AbiJDOSt (ORCPT ); Tue, 4 Oct 2022 10:18:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33002 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229509AbiJDOSr (ORCPT ); Tue, 4 Oct 2022 10:18:47 -0400 Received: from mga03.intel.com (mga03.intel.com [134.134.136.65]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 976AE2FC2F; Tue, 4 Oct 2022 07:18:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1664893125; x=1696429125; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=/ZhcxE23XxY+wRDapL4hQYTPECwVP1wjdbRokWF4C6M=; b=hDxc17rngdiCzrfqOdO0kCB4KrobUCdfwdygSWb6iT21g46hp8EpG7Fc BYfMRpWcIRspHIMcdNeM8UOnm4RUkMa9iZyUDNtnspXfDIpXCltlw/OyY xTHf8pAW0rURgbVN175OhHGCuQnRqXcZloBaaVhgg4Idmne/hdMyx2u4s LgtYTNpffFb5t1gJ1IjfnneApYT99P3VnNL2ktn2VyDX1thVBdlv+DhfW j7yn5WeirC86esm6A8UsPwGj3tBeHbt5iPVqvzzI+TcIdlyJNOI+YE+5o JN3Yu22hPyeID3Pv9wQCq2NpNPlzJrv5UXKV9DPRYny7teMnWkBos4+MY g==; X-IronPort-AV: E=McAfee;i="6500,9779,10490"; a="304464657" X-IronPort-AV: E=Sophos;i="5.95,158,1661842800"; d="scan'208";a="304464657" Received: from orsmga002.jf.intel.com ([10.7.209.21]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 04 Oct 2022 07:18:45 -0700 X-IronPort-AV: E=McAfee;i="6500,9779,10490"; a="623945386" X-IronPort-AV: E=Sophos;i="5.95,158,1661842800"; d="scan'208";a="623945386" Received: from samrober-mobl.amr.corp.intel.com (HELO [10.209.85.136]) ([10.209.85.136]) by orsmga002-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 04 Oct 2022 07:18:44 -0700 Message-ID: <62c6c3a7-3bd2-69ee-36cd-341e11c43978@intel.com> Date: Tue, 4 Oct 2022 07:18:43 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Subject: Re: [PATCH v2 06/39] x86/fpu: Add helper for modifying xstate Content-Language: en-US To: "Edgecombe, Rick P" , "keescook@chromium.org" Cc: "bsingharora@gmail.com" , "hpa@zytor.com" , "Syromiatnikov, Eugene" , "peterz@infradead.org" , "rdunlap@infradead.org" , "dave.hansen@linux.intel.com" , "kirill.shutemov@linux.intel.com" , "Eranian, Stephane" , "linux-mm@kvack.org" , "fweimer@redhat.com" , "nadav.amit@gmail.com" , "jannh@google.com" , "dethoma@microsoft.com" , "linux-arch@vger.kernel.org" , "kcc@google.com" , "bp@alien8.de" , "oleg@redhat.com" , "hjl.tools@gmail.com" , "Yang, Weijiang" , "Lutomirski, Andy" , "pavel@ucw.cz" , "arnd@arndb.de" , "Moreira, Joao" , "tglx@linutronix.de" , "mike.kravetz@oracle.com" , "x86@kernel.org" , "linux-doc@vger.kernel.org" , "jamorris@linux.microsoft.com" , "john.allen@amd.com" , "rppt@kernel.org" , "mingo@redhat.com" , "Shankar, Ravi V" , "corbet@lwn.net" , "linux-kernel@vger.kernel.org" , "linux-api@vger.kernel.org" , "gorcunov@gmail.com" References: <20220929222936.14584-1-rick.p.edgecombe@intel.com> <20220929222936.14584-7-rick.p.edgecombe@intel.com> <202210031045.419F7DB396@keescook> From: Dave Hansen In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/3/22 13:05, Edgecombe, Rick P wrote: > The CET state is xsaves managed. It gets lazily restored before > returning to userspace with the rest of the fpu stuff. This function > will force restore all the fpu state to the registers early and lock > them from being automatically saved/restored. Then the tasks CET state > can be modified in the MSRs, before unlocking the fpregs. Last time I > tried to modify the state directly in the xsave buffer when it was > efficient, but it had issues and Thomas suggested this. Can you get the gist of this in a comment, please?