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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id EB60CC54E5D for ; Thu, 14 Mar 2024 16:20:23 +0000 (UTC) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=intel.com header.i=@intel.com header.a=rsa-sha256 header.s=Intel header.b=aop9IpmF; dkim-atps=neutral Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4TwXfZ3zWQz3vXj for ; Fri, 15 Mar 2024 03:20:22 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=intel.com header.i=@intel.com header.a=rsa-sha256 header.s=Intel header.b=aop9IpmF; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; 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X-IronPort-AV: E=McAfee;i="6600,9927,11013"; a="5464830" X-IronPort-AV: E=Sophos;i="6.07,125,1708416000"; d="scan'208";a="5464830" Received: from fmviesa004.fm.intel.com ([10.60.135.144]) by fmvoesa108.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Mar 2024 09:19:14 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.07,125,1708416000"; d="scan'208";a="16938306" Received: from laallen-mobl.amr.corp.intel.com (HELO [10.209.21.198]) ([10.209.21.198]) by fmviesa004-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Mar 2024 09:19:13 -0700 Message-ID: <6ce6aa20-25d2-4784-823f-2a18f592e002@intel.com> Date: Thu, 14 Mar 2024 09:19:15 -0700 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/1] x86/elf: Add a new .note section containing Xfeatures information to x86 core files Content-Language: en-US To: Borislav Petkov References: <20240314112359.50713-1-vigbalas@amd.com> <20240314112359.50713-2-vigbalas@amd.com> <20240314160824.GDZfMg-J1VOyjxIMiV@fat_crate.local> From: Dave Hansen Autocrypt: addr=dave.hansen@intel.com; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: felix.willgerodt@intel.com, matz@suse.de, keescook@chromium.org, jhb@freebsd.org, bpetkov@amd.com, binutils@sourceware.org, x86@kernel.org, linux-kernel@vger.kernel.org, aneesh.kumar@kernel.org, linux-mm@kvack.org, Vignesh Balasubramanian , npiggin@gmail.com, linux-toolchains@vger.kernel.org, naveen.n.rao@linux.ibm.com, linuxppc-dev@lists.ozlabs.org, jinisusan.george@amd.com, ebiederm@xmission.com Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 3/14/24 09:08, Borislav Petkov wrote: > On Thu, Mar 14, 2024 at 08:37:09AM -0700, Dave Hansen wrote: >> This is pretty close to just a raw dump of the XSAVE CPUID leaves. >> Rather than come up with an XSAVE-specific ABI that depends on CPUID >> *ANYWAY* (because it dumps the "flags" register aka. ECX), maybe we >> should just bite the bullet and dump out (some of) the raw CPUID space. > > Funny you should say that. This was what they had done originally but if > you dump CPUID and you want to add another component in the future which > is *not* described by CPUID, your scheme breaks. Are you envisioning an *XSAVE* state component that's not described by CPUID? Or some _other_ (non-XSAVE) component in a core dump that isn't described by CPUID? > So the idea is to have a self-describing buffers layout, independent > from any x86-ism. You can extend this in a straight-forward way then > later. That argument breaks down a bit on the flags though: xc.xfeat_flags = xstate_flags[i]; Because it comes _directly_ from CPUID with zero filtering: cpuid_count(XSTATE_CPUID, i, &eax, &ebx, &ecx, &edx); ... xstate_flags[i] = ecx; So this layout is quite dependent on what's in x86's CPUID.