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X-CSE-ConnectionGUID: B/zgqoNYS1eQo9k0BueXiA== X-CSE-MsgGUID: pAx6CxzfSHK6Ti2qeu7zLg== X-IronPort-AV: E=McAfee;i="6800,10657,11633"; a="92471060" X-IronPort-AV: E=Sophos;i="6.20,252,1758610800"; d="scan'208";a="92471060" Received: from orviesa001.jf.intel.com ([10.64.159.141]) by fmvoesa101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 Dec 2025 09:30:13 -0800 X-CSE-ConnectionGUID: 0zVgGn7kRryd4YRQDDxvpw== X-CSE-MsgGUID: JpgCbNWPR9SJGQ2HiyIx1Q== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.20,252,1758610800"; d="scan'208";a="232715651" Received: from vverma7-desk1.amr.corp.intel.com (HELO [10.125.108.173]) ([10.125.108.173]) by smtpauth.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 Dec 2025 09:30:11 -0800 Message-ID: <51a059a1-f03a-4b43-8df6-d31fca09cce7@intel.com> Date: Fri, 5 Dec 2025 09:30:09 -0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v8 05/13] KVM: guest_memfd: Add flag to remove from direct map To: "Kalyazin, Nikita" , "kvm@vger.kernel.org" , "linux-doc@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "kvmarm@lists.linux.dev" , "linux-fsdevel@vger.kernel.org" , "linux-mm@kvack.org" , "bpf@vger.kernel.org" , "linux-kselftest@vger.kernel.org" Cc: "pbonzini@redhat.com" , "corbet@lwn.net" , "maz@kernel.org" , "oupton@kernel.org" , "joey.gouly@arm.com" , "suzuki.poulose@arm.com" , "yuzenghui@huawei.com" , "catalin.marinas@arm.com" , "will@kernel.org" , "seanjc@google.com" , "tglx@linutronix.de" , "mingo@redhat.com" , "bp@alien8.de" , "dave.hansen@linux.intel.com" , "x86@kernel.org" , "hpa@zytor.com" , "luto@kernel.org" , "peterz@infradead.org" , "willy@infradead.org" , "akpm@linux-foundation.org" , "david@kernel.org" , "lorenzo.stoakes@oracle.com" , "Liam.Howlett@oracle.com" , "vbabka@suse.cz" , "rppt@kernel.org" , "surenb@google.com" , "mhocko@suse.com" , "ast@kernel.org" , "daniel@iogearbox.net" , "andrii@kernel.org" , "martin.lau@linux.dev" , "eddyz87@gmail.com" , "song@kernel.org" , "yonghong.song@linux.dev" , "john.fastabend@gmail.com" , "kpsingh@kernel.org" , "sdf@fomichev.me" , "haoluo@google.com" , "jolsa@kernel.org" , "jgg@ziepe.ca" , "jhubbard@nvidia.com" , "peterx@redhat.com" , "jannh@google.com" , "pfalcato@suse.de" , "shuah@kernel.org" , "riel@surriel.com" , "baohua@kernel.org" , "ryan.roberts@arm.com" , "jgross@suse.com" , "yu-cheng.yu@intel.com" , "kas@kernel.org" , "coxu@redhat.com" , "kevin.brodsky@arm.com" , "ackerleytng@google.com" , "maobibo@loongson.cn" , "prsampat@amd.com" , "mlevitsk@redhat.com" , "isaku.yamahata@intel.com" , "jmattson@google.com" , "jthoughton@google.com" , "linux-arm-kernel@lists.infradead.org" , "vannapurve@google.com" , "jackmanb@google.com" , "aneesh.kumar@kernel.org" , "patrick.roy@linux.dev" , "Thomson, Jack" , "Itazuri, Takahiro" , "Manwaring, Derek" , "Cali, Marco" References: <20251205165743.9341-1-kalyazin@amazon.com> <20251205165743.9341-6-kalyazin@amazon.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: <20251205165743.9341-6-kalyazin@amazon.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 08BA240025 X-Stat-Signature: c3zemy7j6xgkyfzdctemg7rwa37gza71 X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1764955814-451914 X-HE-Meta: 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 dAje28Ui JNfhBbrAzFP86N0HclCbY2a1clTqcFubUz1WcbcPZqZx9qlsWzHWdGC2kZqLvtD1JA35m3svcBBcRSa5zPNqMVFNV427IqowRdM6OvSyXVeQikF64hubcFdgKmeNoldXY5qp7vV0JQwp8EFtHHmZ9pvks/kxhZ6Rm/dObgzFRw+imyj5gax+6WEnsoy3mrzkcx9QU/KSISFanJVv0N3JiQJFW3yI/TqeR7W2ZAKDC3RV83ECdnerjX/kGMYxL27zFIMOAuzkmkImqMZhtrjkppPqOwF+Pp4eoC2FurrxY7lDHK+gCUfuMM2Fg6K6soDDGWGFQpHm9cg4VoHcz8eckfud+fOhoARKaBoA7Ye0q5yJAbzg= 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 12/5/25 08:58, Kalyazin, Nikita wrote: > +static void kvm_gmem_folio_restore_direct_map(struct folio *folio) > +{ > + /* > + * Direct map restoration cannot fail, as the only error condition > + * for direct map manipulation is failure to allocate page tables > + * when splitting huge pages, but this split would have already > + * happened in set_direct_map_invalid_noflush() in kvm_gmem_folio_zap_direct_map(). > + * Thus set_direct_map_valid_noflush() here only updates prot bits. > + */ > + if (kvm_gmem_folio_no_direct_map(folio)) > + set_direct_map_valid_noflush(folio_page(folio, 0), folio_nr_pages(folio), > + true); > +} This is rather hopeful programming. I can think of a number of ways that this assumption might become invalid. This at *least* check for set_direct_map_valid_noflush() failures (or whatever interface you end up using)? A WARN_ON_ONCE() would be fine.