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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 X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 68765180006 X-Stat-Signature: qcjq34a6b9qzri3p9jd9q5hpm5ounpha X-Rspam-User: X-HE-Tag: 1759423235-919141 X-HE-Meta: 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 /LHj+7Rd CbEBDKKGNSNjHNupA2k40XdlAq/KhvYyEl6TqCbttn/215FQcsRw5QR14LsLqzmjv+XaJ2cMPyouAic8IRICJk6KlLDJj7lDTW5lvPuGO1+k20jM3F06VZaEd5NVUOkusYD2QtUqIWbF1GL/AnR0AsktVPvn9KO+w4dFkS3uVdUlsuGyRELV1wcB+3jKqBWKkldU0eu9wiorIhWk= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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.