From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.7]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 06FCC361653; Tue, 3 Mar 2026 16:27:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.7 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772555248; cv=none; b=Jn1E5HmQIj/aa7CGF/3h7kcvyJ5XRopfPdlRPBUtVAr+LrnPHwg5RCM8guSvLBrvOFm+qnAOKENz5cKkbyVayHPfpzvFLLm5Ld4Hz4G5xvhsAIB/ARXJ6B88kevoKEUJ/q89olCOxKfcV5B5AnC1RCYRQ5fe2+WnMEwk2jEC9j0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772555248; c=relaxed/simple; bh=Ndel+Mmc6YqtxDurpebbQXz8m92fczG0wOpXzsmjQ5g=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=GTyj6fBPjyEyBc+f3zA7tq1G2VTlihyZenjq5T1WSSuTdAKvZz4YakL31TWwxU6sGPRLsGywgU5as2UMFZKJCO5rnmon94H/RIjASewfp1gsbqFtO9adUTTPHE2zOjtwoLi9qvALP1pFcLLcwA6ZZdcsp6SBfYskpdGdF3pMJio= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=dqHKwvAr; arc=none smtp.client-ip=192.198.163.7 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="dqHKwvAr" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1772555243; x=1804091243; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=Ndel+Mmc6YqtxDurpebbQXz8m92fczG0wOpXzsmjQ5g=; b=dqHKwvArJTf60w/Uy+e+O+2H1GZEM1S6w7RB+xpvIbrJebP73KP2JAAh IPU8/pSiHhFFEeO5P3WnU1l3eDXy+vumA2h3DllF76kQBxwI2vDiyC9fV GPZJ63+feRu6GB02qbNdj0zoFBSkq/2rP6Eq2YttuuJhuLq9CEDJuvCOc +0qNo2HtX3ZYNcvu1BFg66ihzKN1xO1zoHce7fC63mkccacLCAqv8oKbv Td+xZyamUE8wXdVyByEEhXE4hZlQOZC2s/fFHNh/jyXc7x9XLeBNwIynu +psI4nFyE1bN3aigQvDIeWUbgz319bHQDSuLhe9tYFgGrn4G1sUF5fDwE w==; X-CSE-ConnectionGUID: UCpfuu0ESyCvLQTfGF+VuQ== X-CSE-MsgGUID: AIl8Wo17TMyWECoD37SzFw== X-IronPort-AV: E=McAfee;i="6800,10657,11718"; a="99073806" X-IronPort-AV: E=Sophos;i="6.21,322,1763452800"; d="scan'208";a="99073806" Received: from fmviesa005.fm.intel.com ([10.60.135.145]) by fmvoesa101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 03 Mar 2026 08:27:22 -0800 X-CSE-ConnectionGUID: HjkZ4ez5S/KqsVbqDKOUTQ== X-CSE-MsgGUID: usoivkydQnCqUatm+a4Gdg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.21,322,1763452800"; d="scan'208";a="222702381" Received: from rchatre-mobl4.amr.corp.intel.com (HELO [10.125.108.135]) ([10.125.108.135]) by fmviesa005-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 03 Mar 2026 08:27:21 -0800 Message-ID: Date: Tue, 3 Mar 2026 08:27:26 -0800 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 0/5] x86: Enable LASS support with vsyscall emulation To: Sohil Mehta , Dave Hansen , x86@kernel.org, Andy Lutomirski , Borislav Petkov Cc: Jonathan Corbet , Shuah Khan , Thomas Gleixner , Ingo Molnar , "H . Peter Anvin" , Peter Zijlstra , Kiryl Shutsemau , Brendan Jackman , Sean Christopherson , Nam Cao , Cedric Xing , Rick Edgecombe , Andrew Cooper , Tony Luck , Alexander Shishkin , Maciej Wieczor-Retman , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260219233600.154313-1-sohil.mehta@intel.com> From: Dave Hansen Content-Language: en-US Autocrypt: addr=dave.hansen@intel.com; keydata= xsFNBE6HMP0BEADIMA3XYkQfF3dwHlj58Yjsc4E5y5G67cfbt8dvaUq2fx1lR0K9h1bOI6fC oAiUXvGAOxPDsB/P6UEOISPpLl5IuYsSwAeZGkdQ5g6m1xq7AlDJQZddhr/1DC/nMVa/2BoY 2UnKuZuSBu7lgOE193+7Uks3416N2hTkyKUSNkduyoZ9F5twiBhxPJwPtn/wnch6n5RsoXsb ygOEDxLEsSk/7eyFycjE+btUtAWZtx+HseyaGfqkZK0Z9bT1lsaHecmB203xShwCPT49Blxz VOab8668QpaEOdLGhtvrVYVK7x4skyT3nGWcgDCl5/Vp3TWA4K+IofwvXzX2ON/Mj7aQwf5W iC+3nWC7q0uxKwwsddJ0Nu+dpA/UORQWa1NiAftEoSpk5+nUUi0WE+5DRm0H+TXKBWMGNCFn c6+EKg5zQaa8KqymHcOrSXNPmzJuXvDQ8uj2J8XuzCZfK4uy1+YdIr0yyEMI7mdh4KX50LO1 pmowEqDh7dLShTOif/7UtQYrzYq9cPnjU2ZW4qd5Qz2joSGTG9eCXLz5PRe5SqHxv6ljk8mb ApNuY7bOXO/A7T2j5RwXIlcmssqIjBcxsRRoIbpCwWWGjkYjzYCjgsNFL6rt4OL11OUF37wL QcTl7fbCGv53KfKPdYD5hcbguLKi/aCccJK18ZwNjFhqr4MliQARAQABzUVEYXZpZCBDaHJp c3RvcGhlciBIYW5zZW4gKEludGVsIFdvcmsgQWRkcmVzcykgPGRhdmUuaGFuc2VuQGludGVs LmNvbT7CwXgEEwECACIFAlQ+9J0CGwMGCwkIBwMCBhUIAgkKCwQWAgMBAh4BAheAAAoJEGg1 lTBwyZKwLZUP/0dnbhDc229u2u6WtK1s1cSd9WsflGXGagkR6liJ4um3XCfYWDHvIdkHYC1t MNcVHFBwmQkawxsYvgO8kXT3SaFZe4ISfB4K4CL2qp4JO+nJdlFUbZI7cz/Td9z8nHjMcWYF IQuTsWOLs/LBMTs+ANumibtw6UkiGVD3dfHJAOPNApjVr+M0P/lVmTeP8w0uVcd2syiaU5jB aht9CYATn+ytFGWZnBEEQFnqcibIaOrmoBLu2b3fKJEd8Jp7NHDSIdrvrMjYynmc6sZKUqH2 I1qOevaa8jUg7wlLJAWGfIqnu85kkqrVOkbNbk4TPub7VOqA6qG5GCNEIv6ZY7HLYd/vAkVY E8Plzq/NwLAuOWxvGrOl7OPuwVeR4hBDfcrNb990MFPpjGgACzAZyjdmYoMu8j3/MAEW4P0z F5+EYJAOZ+z212y1pchNNauehORXgjrNKsZwxwKpPY9qb84E3O9KYpwfATsqOoQ6tTgr+1BR CCwP712H+E9U5HJ0iibN/CDZFVPL1bRerHziuwuQuvE0qWg0+0SChFe9oq0KAwEkVs6ZDMB2 P16MieEEQ6StQRlvy2YBv80L1TMl3T90Bo1UUn6ARXEpcbFE0/aORH/jEXcRteb+vuik5UGY 5TsyLYdPur3TXm7XDBdmmyQVJjnJKYK9AQxj95KlXLVO38lczsFNBFRjzmoBEACyAxbvUEhd GDGNg0JhDdezyTdN8C9BFsdxyTLnSH31NRiyp1QtuxvcqGZjb2trDVuCbIzRrgMZLVgo3upr MIOx1CXEgmn23Zhh0EpdVHM8IKx9Z7V0r+rrpRWFE8/wQZngKYVi49PGoZj50ZEifEJ5qn/H Nsp2+Y+bTUjDdgWMATg9DiFMyv8fvoqgNsNyrrZTnSgoLzdxr89FGHZCoSoAK8gfgFHuO54B lI8QOfPDG9WDPJ66HCodjTlBEr/Cwq6GruxS5i2Y33YVqxvFvDa1tUtl+iJ2SWKS9kCai2DR 3BwVONJEYSDQaven/EHMlY1q8Vln3lGPsS11vSUK3QcNJjmrgYxH5KsVsf6PNRj9mp8Z1kIG qjRx08+nnyStWC0gZH6NrYyS9rpqH3j+hA2WcI7De51L4Rv9pFwzp161mvtc6eC/GxaiUGuH BNAVP0PY0fqvIC68p3rLIAW3f97uv4ce2RSQ7LbsPsimOeCo/5vgS6YQsj83E+AipPr09Caj 0hloj+hFoqiticNpmsxdWKoOsV0PftcQvBCCYuhKbZV9s5hjt9qn8CE86A5g5KqDf83Fxqm/ vXKgHNFHE5zgXGZnrmaf6resQzbvJHO0Fb0CcIohzrpPaL3YepcLDoCCgElGMGQjdCcSQ+Ci FCRl0Bvyj1YZUql+ZkptgGjikQARAQABwsFfBBgBAgAJBQJUY85qAhsMAAoJEGg1lTBwyZKw l4IQAIKHs/9po4spZDFyfDjunimEhVHqlUt7ggR1Hsl/tkvTSze8pI1P6dGp2XW6AnH1iayn yRcoyT0ZJ+Zmm4xAH1zqKjWplzqdb/dO28qk0bPso8+1oPO8oDhLm1+tY+cOvufXkBTm+whm +AyNTjaCRt6aSMnA/QHVGSJ8grrTJCoACVNhnXg/R0g90g8iV8Q+IBZyDkG0tBThaDdw1B2l asInUTeb9EiVfL/Zjdg5VWiF9LL7iS+9hTeVdR09vThQ/DhVbCNxVk+DtyBHsjOKifrVsYep WpRGBIAu3bK8eXtyvrw1igWTNs2wazJ71+0z2jMzbclKAyRHKU9JdN6Hkkgr2nPb561yjcB8 sIq1pFXKyO+nKy6SZYxOvHxCcjk2fkw6UmPU6/j/nQlj2lfOAgNVKuDLothIxzi8pndB8Jju KktE5HJqUUMXePkAYIxEQ0mMc8Po7tuXdejgPMwgP7x65xtfEqI0RuzbUioFltsp1jUaRwQZ MTsCeQDdjpgHsj+P2ZDeEKCbma4m6Ez/YWs4+zDm1X8uZDkZcfQlD9NldbKDJEXLIjYWo1PH hYepSffIWPyvBMBTW2W5FRjJ4vLRrJSUoEfJuPQ3vW9Y73foyo/qFoURHO48AinGPZ7PC7TF vUaNOTjKedrqHkaOcqB185ahG2had0xnFsDPlx5y In-Reply-To: <20260219233600.154313-1-sohil.mehta@intel.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 2/19/26 15:35, Sohil Mehta wrote: > These patches primarily update the #GP handler to reuse the existing > vsyscall emulation code for #PF. In XONLY mode, the faulting RIP is > readily available and can be used to determine if the #GP was triggered > due to a vsyscall access. > > In contrast, the vsyscall EMULATE mode is deprecated and not expected to > be used by anyone. Supporting EMULATE mode with LASS would require > complex instruction decoding in the #GP fault handler, which is not > worth the effort. So, LASS is disabled in the rare case when someone > absolutely needs to enable vsyscall=emulate via the command line. So this part is actually pretty nice. Could we forklift a bit of this into patch 3, please?