From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.14]) (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 63CE68493 for ; Tue, 14 Jan 2025 21:13:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.14 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736889218; cv=none; b=j658CkgpFox48sblv4QRSoo+dKr4GYTAgOLdJX9OmOIPnHKukMULyJ4gtFYCHcWBeXacmCkbEukAdxtWTcD3o8WO2xcdaT5bb4sGN0+wq2fgIZRqmOsGRCzlrI4DMmqFa+l7DSURp1Xrna849rUICpit8SVHBNtL1gQNpudYS9M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736889218; c=relaxed/simple; bh=J3ymm9w3WYNsLhV8wbULRhYEQZZ6MZBsqGcYuuiCyPo=; h=Message-ID:Date:MIME-Version:Subject:To:References:From: In-Reply-To:Content-Type; b=iYDruBUuQypr1Wb8BAL2lzLSe6lwA5pW5C7ivYO4eGoLQm3stTU7WZMgOo9znT+Pj2MdVUH9Y297UgV7NqNctddcX2oWa0MDl0LEDT6r5RCsGLMRiy1xR8LLItdlURgxtenhQuP64n/PpYl6s7vq1kQVb1IdkZHWRKvh7QhdlgI= 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=KPuEHOoa; arc=none smtp.client-ip=192.198.163.14 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="KPuEHOoa" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1736889217; x=1768425217; h=message-id:date:mime-version:subject:to:references:from: in-reply-to:content-transfer-encoding; bh=J3ymm9w3WYNsLhV8wbULRhYEQZZ6MZBsqGcYuuiCyPo=; b=KPuEHOoai7PIznU3IJpwXBmBN2/vSdo9lb5cXDEAOAemR6ohAbDfT2OJ fzupJMKV+XhZ3GTjlUpRNIHHLYQwmXqcilc/UdbFgsDjx4oIKIUYT85gv bm2Po1nkzxmMg5+u++kQe4EofyMTT1xZ0f+MzisMJsWgPKTixs7mvOtJ2 yBMM0BjkAe7UilwOY6Pr6c+pMRz8Z60kmqmBO7bmsMKA/SNg6CvZUkq8N 903pnMeUGMorPx2KR5XmKcYyVTpZJh29EjEruZ1+chka+xSVzXVJSrUsc TcL47eOEzZIhgRRv5NbuKd3ST0sDEkiUVKlLNjHplQZLvr6KKGiG3zbLL A==; X-CSE-ConnectionGUID: VZFv2mHCSryxQc+Q9y4KAw== X-CSE-MsgGUID: MIrzwm3hQzCmolewJLX0CA== X-IronPort-AV: E=McAfee;i="6700,10204,11315"; a="37435103" X-IronPort-AV: E=Sophos;i="6.12,315,1728975600"; d="scan'208";a="37435103" Received: from fmviesa006.fm.intel.com ([10.60.135.146]) by fmvoesa108.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Jan 2025 13:13:36 -0800 X-CSE-ConnectionGUID: +uYbSsCRSSmjGJw5Tro4CA== X-CSE-MsgGUID: F+3+aPUxRS2PkiwvA4ifLw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.12,315,1728975600"; d="scan'208";a="104768272" Received: from ssimmeri-mobl2.amr.corp.intel.com (HELO [10.124.223.199]) ([10.124.223.199]) by fmviesa006-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Jan 2025 13:13:35 -0800 Message-ID: Date: Tue, 14 Jan 2025 13:13:36 -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: untagged_addr_remote() in do_madvise() To: Lorenzo Stoakes , "Liam R. Howlett" , dave.hansen@linux.intel.com, kirill.shutemov@linux.intel.com, Shakeel Butt , SeongJae Park , David Hildenbrand , Vlastimil Babka , Andrew Morton , Jens Axboe , Pavel Begunkov , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Ryan Roberts References: Content-Language: en-US From: Dave Hansen 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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 1/14/25 12:41, Lorenzo Stoakes wrote: ... > However, MADV_HWPOISON, MADV_SOFT_OFFLINE seems fundamentally broken for tagged > addresses: > > #ifdef CONFIG_MEMORY_FAILURE > if (behavior == MADV_HWPOISON || behavior == MADV_SOFT_OFFLINE) > return madvise_inject_error(behavior, start, start + len_in); > #endif > > ^ this is invoked before untagged_addr_remote() is called (as no mmap lock is > acquired) and so no attempt at untagging happens at all...! Except this call path: madvise_inject_error() -> get_user_pages_fast() -> gup_fast_fallback() does its own untagging: start = untagged_addr(start) & PAGE_MASK; It might also have some funky behavior if start+len_in overflows. But, just as in the other case, it's invalid to begin with so I think userspace kinda gets to keep the pieces. But I do 100% agree that this is non-obvious. In a perfect world, tagged addresses would get untagged at the user/kernel boundary in _one_ choke point. But the world is hard and that would make things too easy and then we wouldn't get paid the big bucks. ;) To clarify things, I don't think it'd be the worst thing to just move the madvise_inject_error() down and have that case acquire mmap_read_lock(). Sure, it's not required, but it's basically debugging code and I can't imagine it's avoiding the lock for performance reasons.