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bh=s99HHxZBXzZk9cxzGguqQQ4N8Es8DeZ5bwewpR7hcH8=; b=A+8HskCK8+KYPq84pv6Ejg9yEpTtlriV+GpkbPg+0p3ph/5nnlRO1pm0 WoQC53g6Ssj2JI9u5NgQHUTwVpHaKXy3l8ehHLJ4cYZgJanbMKmq7Dwfa GclEVKw1liCRGBJg0vxK6r9u+1LKm+//Kgpy6du/6z+rvq+AHdMunnBhg gnj2OXuaNaPkECTPlSuA1XcOib4399vlhcyJWByjuL6hVwoeK+6aKg0bO O9U9rykrLuDde6Wxr1xtTbrdpkEnJ5A9BO1EUgSw5feE5hu6xa2P8b1EI dtCXbUW6SMheHcbvVeB0WjBz6Fejhn3jDFCiTJ5uiGo/YReh6M7nOobYF A==; X-IronPort-AV: E=McAfee;i="6600,9927,11013"; a="5464820" X-IronPort-AV: E=Sophos;i="6.07,125,1708416000"; d="scan'208";a="5464820" 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 Precedence: bulk X-Mailing-List: linux-kernel@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, bpetkov@amd.com, 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> From: Dave Hansen Autocrypt: addr=dave.hansen@intel.com; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 3/14/24 09:08, 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.