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X-CSE-ConnectionGUID: /XXQLHImSvCA3P3G8B39hA== X-CSE-MsgGUID: NWr6aMcvQ6SlcIWD5HSbjw== X-IronPort-AV: E=McAfee;i="6700,10204,11325"; a="37546363" X-IronPort-AV: E=Sophos;i="6.13,232,1732608000"; d="scan'208";a="37546363" Received: from orviesa001.jf.intel.com ([10.64.159.141]) by fmvoesa112.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Jan 2025 11:12:54 -0800 X-CSE-ConnectionGUID: qCXpZtA4Rfyv9V5aL/OxCA== X-CSE-MsgGUID: eXURZ4/VRGWjCAaH0Fschg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.12,224,1728975600"; d="scan'208";a="145086634" Received: from pgcooper-mobl3.ger.corp.intel.com (HELO [10.245.244.10]) ([10.245.244.10]) by smtpauth.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Jan 2025 11:12:46 -0800 Message-ID: Date: Fri, 24 Jan 2025 11:12:45 -0800 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: [RFC][PATCH 0/8] x86/mm: Simplify PAE page table handling To: Joerg Roedel Cc: Peter Zijlstra , Dave Hansen , linux-kernel@vger.kernel.org, x86@kernel.org, tglx@linutronix.de, bp@alien8.de, luto@kernel.org, kirill.shutemov@linux.intel.com, rick.p.edgecombe@intel.com, jgross@suse.com References: <20250123172428.D6D8C8D9@davehans-spike.ostc.intel.com> <20250123214911.GB969@noisy.programming.kicks-ass.net> <6c1785c8-e74e-4912-95bb-88b6e94f544f@intel.com> From: Dave Hansen Content-Language: en-US Autocrypt: addr=dave.hansen@intel.com; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 1/23/25 23:58, Joerg Roedel wrote: > On Thu, Jan 23, 2025 at 03:06:26PM -0800, Dave Hansen wrote: >> 32-bit+PTI or 32-bit in general? ;) > > +1 for removing x86-32 bit support alltogether. > >> I'm curious what Joerg and the other folks that worked on 32-bit PTI >> think about it in retrospect. The 32 vs. 64-bit security gap was >> probably modest in 2018 and it can only have grown since then. > > I think the decision to keep and maintain 32-bit support only makes > sense if it can be kept on-par with x86-64 security-wise, otherwise we > are lying to our users about the 'supported' part. Back in the day when > I did the 32-bit PTI support it made sense, but that was 7 years ago. > > When was the last 32-bit only x86 CPU sold? Probably INTEL_QUARK_X1000, but it was mostly a toy. It's family 5, so this applies: static const __initconst struct x86_cpu_id cpu_vuln_whitelist[] = { ... VULNWL(INTEL, 5, X86_MODEL_ANY, NO_SPECULATION), Here's one that was released in 2015, probably just for embedded use: > https://www.intel.com/content/www/us/en/products/sku/91947/intel-quark-microcontroller-d2000/specifications.html There were some Atoms in 2008 that seem to have had the 64-bit support fused off. They were probably the last normal CPU that someone would have in a PC that didn't have 64-bit support. > https://www.intel.com/content/www/us/en/ark/products/codename/24976/products-formerly-silverthorne.html > https://www.intel.com/content/www/us/en/products/sku/36331/intel-atom-processor-n270-512k-cache-1-60-ghz-533-mhz-fsb/specifications.html But these are also NO_SPECULATION, so don't need most of the mitigations.