From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.14]) (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 A4D081448E0 for ; Fri, 23 Feb 2024 19:39:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.14 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708717150; cv=none; b=RdWdguIb75gpSJP6eIcjajjjC/KD0awpsh7XyBcQL2ZVSZ2+N2CCdjwMMw/L8DdnnfA+IStin5mNZmRepiYyQLP81GwtIC8isxZVrp8nG4ZXQwXIpcYyhJwRkUnHjfKX8Gkl2Xo+gB6jYMN2mBxqiiFpoymspA3P1lxw5LlC4Us= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708717150; c=relaxed/simple; bh=pLrNYUAa8YeswxINnrU38+oxEExh3rDUsw3BEb0+Vvg=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=doH7lU8z3yqQMHQ5S8w/XLf6YU7zBNtJmMsf+xmfB+DGNSxBzxDdZaLtfHg0B+QpsT9sFtTwwJ5sR/why43CeY0kkKyYt/8OX8zUD7WggZzGGz7YT8+Vmv9x0pCqxTqLmNbEaeRe7tFosM88G/2fxVoUgJX4rChHVBHQTjQ0qPo= 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=E/AJ5O5h; arc=none smtp.client-ip=198.175.65.14 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="E/AJ5O5h" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1708717148; x=1740253148; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=pLrNYUAa8YeswxINnrU38+oxEExh3rDUsw3BEb0+Vvg=; b=E/AJ5O5hlNM9y5cWqYKsxCdYckt1P62xsi2MZNScgi7U2d8VOPVWpMNP pE9yY4PD48Q3Qqwld0HtOFUTVheD/p7YYKO02RdAT6KH9Zw1t/bnt2JWp rMSmWDV6T9Z8Jgf34y/ucLIP4fovCytVXXQfXlnO+T/rOqEUDZxArz6cC KMnDKZoSrE0x+5NNUdu4xdBtPLQg3rdegeItjfBnmjZzhneD+vARCniI7 7L2bjR2qFmgsvOquoBl8cwnnqbSnYI1sUFEmxwel001hlPrKgEVQj4aOC Neay6mu5x1zF09cL+KKLhGC7AMQEbdsOqismh2q7ZG3cCF+V/ozFYTbvs g==; X-IronPort-AV: E=McAfee;i="6600,9927,10993"; a="6867192" X-IronPort-AV: E=Sophos;i="6.06,180,1705392000"; d="scan'208";a="6867192" Received: from orviesa002.jf.intel.com ([10.64.159.142]) by orvoesa106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Feb 2024 11:39:08 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.06,180,1705392000"; d="scan'208";a="36778758" Received: from gtkramer-mobl1.amr.corp.intel.com (HELO [10.209.82.163]) ([10.209.82.163]) by orviesa002-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Feb 2024 11:39:08 -0800 Message-ID: Date: Fri, 23 Feb 2024 11:39:07 -0800 Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCHv7 10/16] x86/tdx: Convert shared memory back to private on kexec Content-Language: en-US To: "Kirill A. Shutemov" , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org Cc: "Rafael J. Wysocki" , Peter Zijlstra , Adrian Hunter , Kuppuswamy Sathyanarayanan , Elena Reshetova , Jun Nakajima , Rick Edgecombe , Tom Lendacky , "Kalra, Ashish" , Sean Christopherson , "Huang, Kai" , Baoquan He , kexec@lists.infradead.org, linux-coco@lists.linux.dev, linux-kernel@vger.kernel.org References: <20240212104448.2589568-1-kirill.shutemov@linux.intel.com> <20240212104448.2589568-11-kirill.shutemov@linux.intel.com> 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: <20240212104448.2589568-11-kirill.shutemov@linux.intel.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 2/12/24 02:44, Kirill A. Shutemov wrote: > +static void tdx_kexec_stop_conversion(bool crash) > +{ > + /* Stop new private<->shared conversions */ > + conversion_allowed = false; > + > + /* > + * Make sure conversion_allowed is cleared before checking > + * conversions_in_progress. > + */ > + barrier(); > + > + /* > + * Crash kernel reaches here with interrupts disabled: can't wait for > + * conversions to finish. > + * > + * If race happened, just report and proceed. > + */ > + if (!crash) { > + unsigned long timeout; > + > + /* > + * Wait for in-flight conversions to complete. > + * > + * Do not wait more than 30 seconds. > + */ > + timeout = 30 * USEC_PER_SEC; > + while (atomic_read(&conversions_in_progress) && timeout--) > + udelay(1); > + } > + > + if (atomic_read(&conversions_in_progress)) > + pr_warn("Failed to finish shared<->private conversions\n"); > +} I'd really prefer we find a way to do this with actual locks, especially 'conversion_allowed'. This is _awfully_ close to being able to be handled by a rwsem where the readers are the converters and tdx_kexec_stop_conversion() takes a write.