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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@linux.dev References: <20250924-b4-asi-page-alloc-v1-0-2d861768041f@google.com> <20250924-b4-asi-page-alloc-v1-4-2d861768041f@google.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: <20250924-b4-asi-page-alloc-v1-4-2d861768041f@google.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: E0AE840003 X-Stat-Signature: qz8h5qqqhhh93fdrz5nrwzagu61r9htx X-HE-Tag: 1759350497-540777 X-HE-Meta: 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 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 9/24/25 07:59, Brendan Jackman wrote: > Create the initial shared pagetable to hold all the mappings that will > be shared among ASI domains. > > Mirror the physmap into the ASI pagetables, but with a maximum > granularity that's guaranteed to allow changing pageblock sensitivity > without having to allocate pagetables, and with everything as > non-present. Could you also talk about what this granularity _actually_ is and why it has the property of never requiring page table alloc ... > diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c > index e98e85cf15f42db669696ba8195d8fc633351b26..7e0471d46767c63ceade479ae0d1bf738f14904a 100644 > --- a/arch/x86/mm/init_64.c > +++ b/arch/x86/mm/init_64.c > @@ -7,6 +7,7 @@ > * Copyright (C) 2002,2003 Andi Kleen > */ > > +#include > #include > #include > #include > @@ -746,7 +747,8 @@ phys_pgd_init(pgd_t *pgd_page, unsigned long paddr_start, unsigned long paddr_en > { > unsigned long vaddr, vaddr_start, vaddr_end, vaddr_next, paddr_last; > > - *pgd_changed = false; > + if (pgd_changed) > + *pgd_changed = false; This 'pgd_changed' hunk isn't mentioned in the changelog. ... > @@ -797,6 +800,24 @@ __kernel_physical_mapping_init(unsigned long paddr_start, > > paddr_last = phys_pgd_init(init_mm.pgd, paddr_start, paddr_end, page_size_mask, > prot, init, &pgd_changed); > + > + /* > + * Set up ASI's unrestricted physmap. This needs to mapped at minimum 2M > + * size so that regions can be mapped and unmapped at pageblock > + * granularity without requiring allocations. > + */ This took me a minute to wrap my head around. Here, I think you're trying to convey that: 1. There's a higher-level design decision that all sensitivity will be done at a 2M granularity. A 2MB physical region is either sensitive or not. 2. Because of #1, 1GB mappings are not cool because splitting a 1GB mapping into 2MB needs to allocate a page table page. 3. 4k mappings are OK because they can also have their permissions changed at a 2MB granularity. It's just more laborious. The "minimum 2M size" comment really threw me off because that, to me, also includes 1G which is a no-no here. I also can't help but wonder if it would have been easier and more straightforward to just start this whole exercise at 4k: force all the ASI tables to be 4k. Then, later, add the 2MB support and tie to pageblocks on after. > + if (asi_nonsensitive_pgd) { > + /* > + * Since most memory is expected to end up sensitive, start with > + * everything unmapped in this pagetable. > + */ > + pgprot_t prot_np = __pgprot(pgprot_val(prot) & ~_PAGE_PRESENT); > + > + VM_BUG_ON((PAGE_SHIFT + pageblock_order) < page_level_shift(PG_LEVEL_2M)); > + phys_pgd_init(asi_nonsensitive_pgd, paddr_start, paddr_end, 1 << PG_LEVEL_2M, > + prot_np, init, NULL); > + } I'm also kinda wondering what the purpose is of having a whole page table full of !_PAGE_PRESENT entries. It would be nice to know how this eventually gets turned into something useful.