From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.10]) (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 95DF0261B9C for ; Thu, 2 Oct 2025 16:40:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.10 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759423236; cv=none; b=UGQf0pJ5KaiUmPI7pWwj4TgNfdmkYeIvxQgJGuK709yjhK0Fq+0aI5/NojOQcxqQ+KP0l9fqaLsjYHENLCnHYbbcKvtSQZ1MDRm4c7yJFh1d8xH5ZMh037XfHRNspKnVvsewAQvvqt7quWZSlTPU1OwfA7P90q018S/fsk+Mtec= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759423236; c=relaxed/simple; bh=ibke5hIrVui4nGEtrIYn9QjlwZMC043RVeGvmwn63Ww=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Sbelz4SQmW9Lwe8GMfdoRvxAO6L1D7Mairvwo7bH6KuN94pP8/BOj0BXeqKHMcBOTXO6wBebtW2jFVwBuTgk42wZCTH4xqzRomOCqOX+WlELrDbSX+hMsLZSeBvAKyDN9U0iO+pTt2GbFws2yRhCSA2/fhdc4n1DTo/ug0u1Nn4= 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=hSgvXyjT; arc=none smtp.client-ip=198.175.65.10 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="hSgvXyjT" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1759423234; x=1790959234; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=ibke5hIrVui4nGEtrIYn9QjlwZMC043RVeGvmwn63Ww=; b=hSgvXyjT3DHqAfoWFP5Cp+tWXDaDSqEHhEYUFjXthPNNXL7iT96wtnzb ZooHof9dl92qGOJ+OHmLYyVRWjeaBAjpCQJuK5estSBemaInHeLMsYwIH zidshsY9pTv7Q9cKSjj6jTaRssniTDPkkT4q5PvaNLs3Y/AO1VOY3VPNt xrO8U3FdPjCOZJ4/7cux5o0RAEnr6//1F1hH4LpwUuAPQOzaUTTWlKrGD IsXxFvUhzSSK/9Ccb2dDwmIKWIKYXIdyKukYgPH0sr6Z10gLKgGd3L9Ry td4b1KaMdmkK3oEsRgkuOYeCI9aT2nBR3pcle8VbOICCnshDg+3d84bHi w==; X-CSE-ConnectionGUID: eBP5Onp/RV2cUTM2GfQXaA== X-CSE-MsgGUID: J275H933RqaWHLEGmQgt1g== X-IronPort-AV: E=McAfee;i="6800,10657,11570"; a="79135883" X-IronPort-AV: E=Sophos;i="6.18,310,1751266800"; d="scan'208";a="79135883" Received: from fmviesa005.fm.intel.com ([10.60.135.145]) by orvoesa102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Oct 2025 09:40:29 -0700 X-CSE-ConnectionGUID: 8u4u+yw2TUab9+EwTMdbRg== X-CSE-MsgGUID: IdoaEtPSQkufnv7O5PzOhw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.18,310,1751266800"; d="scan'208";a="183484713" Received: from aschofie-mobl2.amr.corp.intel.com (HELO [10.125.109.249]) ([10.125.109.249]) by fmviesa005-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Oct 2025 09:40:28 -0700 Message-ID: <19e5012a-3c58-4696-9e4e-39e2b7d2b5af@intel.com> Date: Thu, 2 Oct 2025 09:40:27 -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 05/21] x86/mm/pat: mirror direct map changes to ASI To: Brendan Jackman , Andy Lutomirski , Lorenzo Stoakes , "Liam R. Howlett" , Suren Baghdasaryan , Michal Hocko , Johannes Weiner , Zi Yan , Axel Rasmussen , Yuanchu Xie , Roman Gushchin Cc: peterz@infradead.org, bp@alien8.de, dave.hansen@linux.intel.com, mingo@redhat.com, tglx@linutronix.de, akpm@linux-foundation.org, david@redhat.com, derkling@google.com, junaids@google.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, reijiw@google.com, rientjes@google.com, rppt@kernel.org, vbabka@suse.cz, x86@kernel.org, Yosry Ahmed References: <20250924-b4-asi-page-alloc-v1-0-2d861768041f@google.com> <20250924-b4-asi-page-alloc-v1-5-2d861768041f@google.com> <08338619-6aa1-4905-bdf8-bf1a90857307@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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 10/2/25 07:31, Brendan Jackman wrote: > On Wed Oct 1, 2025 at 8:50 PM UTC, Dave Hansen wrote: ... >> But let's say someone is doing something silly like: >> >> set_memory_np(addr, size); >> set_memory_p(addr, size); >> >> Won't that end up in here and make the "unrestricted PGD" have >> _PAGE_PRESENT==1 entries? > > Er, yes, that's a bug, thanks for pointing this out. I guess this is > actually broken under debug_pagealloc or something? I should check that. > > This code should only mirror the bits that are irrelevant to ASI. It's actually anything that has _PAGE_PRESENT in cpa->mask_set. There are a number of those. Some of them are irrelevant like the execmem code, but there are quite a few more that look troublesome outside of debugging environments. >> Also, could we try and make the nomenclature consistent? We've got >> "unrestricted direct map" and "asi_nonsensitive_pgd" being used (at >> least). Could the terminology be made more consistent? > > Hm. It is actually consistent: "unrestricted" is a property of the > address space / execution context. "nonsensitive" is a property of the > memory. Nonsensitive memory is mapped into the unrestricted address > space. asi_nonsensitive_pgd isn't an address space we enter it's just a > holding area (like if we never actually pointed CR3 at init_mm.pgd but > just useed it as a source to clone from). > > However.. just because it's consistent doesn't mean it's not confusing. > Do you think we should just squash these two words and call the whole > thing "nonsensitive"? I don't know if "nonsensitive address space" makes > much sense... Is it possible I can fix this by just adding more > comments? It makes sense to me that a "nonsensitive address space" would not map any sensitive data and that a "asi_nonsensitive_pgd" is the root of that address space. >>> static int __change_page_attr_set_clr(struct cpa_data *cpa, int primary) >>> { >>> unsigned long numpages = cpa->numpages; >>> @@ -2007,6 +2033,8 @@ static int __change_page_attr_set_clr(struct cpa_data *cpa, int primary) >>> if (!debug_pagealloc_enabled()) >>> spin_lock(&cpa_lock); >>> ret = __change_page_attr(cpa, primary); >>> + if (!ret) >>> + ret = mirror_asi_direct_map(cpa, primary); >>> if (!debug_pagealloc_enabled()) >>> spin_unlock(&cpa_lock); >>> if (ret) >>> >> >> Is cpa->pgd ever have any values other than NULL or init_mm->pgd? I >> didn't see anything in a quick grep. > > It can also be efi_mm.pgd via sev_es_efi_map_ghcbs_cas(). It would be _nice_ if the ASI exclusion wasn't so magic. Like, instead of hooking in to __change_page_attr_set_clr() and filtering on init_mm if we had the callers declare explicitly whether their changes get reflected into the ASI nonsensitive PGD. Maybe that looks like a new flag: CPA_DIRECT_MAP or something. Once you pass that flag in, the cpa code knows that you're working on init_mm.pgd and mirror_asi_direct_map() can look for *that* instead of init_mm.