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X-IronPort-AV: E=McAfee;i="6600,9927,11013"; a="5116165" X-IronPort-AV: E=Sophos;i="6.07,125,1708416000"; d="scan'208";a="5116165" Received: from orviesa004.jf.intel.com ([10.64.159.144]) by fmvoesa112.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Mar 2024 09:39:50 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.07,125,1708416000"; d="scan'208";a="17014261" Received: from laallen-mobl.amr.corp.intel.com (HELO [10.209.21.198]) ([10.209.21.198]) by orviesa004-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Mar 2024 09:39:50 -0700 Message-ID: <24f71d52-0891-4cfc-8dec-9f13ed618eee@intel.com> Date: Thu, 14 Mar 2024 09:39:51 -0700 Precedence: bulk X-Mailing-List: linux-toolchains@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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 Cc: Vignesh Balasubramanian , linux-kernel@vger.kernel.org, linux-toolchains@vger.kernel.org, mpe@ellerman.id.au, npiggin@gmail.com, christophe.leroy@csgroup.eu, aneesh.kumar@kernel.org, naveen.n.rao@linux.ibm.com, ebiederm@xmission.com, keescook@chromium.org, x86@kernel.org, linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org, jinisusan.george@amd.com, matz@suse.de, binutils@sourceware.org, jhb@freebsd.org, felix.willgerodt@intel.com References: <20240314112359.50713-1-vigbalas@amd.com> <20240314112359.50713-2-vigbalas@amd.com> <20240314160824.GDZfMg-J1VOyjxIMiV@fat_crate.local> <6ce6aa20-25d2-4784-823f-2a18f592e002@intel.com> <20240314162954.GAZfMmAnYQoRjRbRzc@fat_crate.local> From: Dave Hansen Autocrypt: addr=dave.hansen@intel.com; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 3/14/24 09:29, Borislav Petkov wrote: > >> 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. > Yeah, no, this should not be copying CPUID flags - those flags should be > *translated* to independently defined flags which describe those > buffers. Ditto for: xc.xfeat_type = i; Right now, that's bound to CPUID and XSAVE. "feat_type==10" can only ever be PKRU and that's derived from the XSAVE architecture. If you want this to be extensible to things outside of the XSAVE architecture, it needs to be something actually extensible and not entangled with XSAVE. In other words "xc.xfeat_type" can enumerate XSAVE state components being in the dump, but it should not be limited to XSAVE. Just as an example: enum feat_type { FEATURE_XSAVE_PKRU, FEATURE_XSAVE__YMM, FEATURE_XSAVE_BNDREGS, FEATURE_XSAVE_BNDCSR, ... RANDOM_STATE_NOT_XSAVE }; See how feat_type==1 is PKRU and *NOT* feat_type==10? That opens the door to RANDOM_STATE_NOT_XSAVE or anything else you want. This would be _actually_ extensible.