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b=GGFEabRWsR0NmmRAYjKK0QnagsaLpG1VVhv/wQMslI79amhm14y7ppsKtm+3oR/JO ALqWzvnhsTiDDdaiz60YTm87Ksz+E+TbsKhoF+bu5CbiWgKT+fJA9BP6s3/JrPpFZ6 c68j5J9nFq0GxjPkhGDC/tNSypWPWZ0/Kzl/V5/BCmiBe1KUEftCBAPt7PAyorRBXh tTSIXpFyvvkeWfFFflYZ3qI+sIw+SkzK5aTotneLCQeF3LCtUeXag/2E7AEcfEJDBr XLVhK5PhzgKICaHnCaoSkklm+XBuwhLsefpOKNI/YpX9UvHlgICuE6yvuTETC0HcWL ojpZb7YuCu1LQ== Message-ID: <412359f2-ecfb-498a-9717-f0a442abd3f7@kernel.org> Date: Sat, 7 Feb 2026 22:25:28 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCHv6 11/17] mm/hugetlb: Remove fake head pages To: Usama Arif , Kiryl Shutsemau , Andrew Morton , Muchun Song , Matthew Wilcox , Frank van der Linden Cc: Oscar Salvador , Mike Rapoport , Vlastimil Babka , Lorenzo Stoakes , Zi Yan , Baoquan He , Michal Hocko , Johannes Weiner , Jonathan Corbet , Huacai Chen , WANG Xuerui , Palmer Dabbelt , Paul Walmsley , Albert Ou , Alexandre Ghiti , kernel-team@meta.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, loongarch@lists.linux.dev, linux-riscv@lists.infradead.org References: <20260202155634.650837-1-kas@kernel.org> <20260202155634.650837-12-kas@kernel.org> <907ff793-9b02-4a22-a85e-2873246f6402@gmail.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: pes4tt1hsb9er7tuzrgx3cy1wnotazdy X-Rspamd-Queue-Id: CB32D80005 X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1770499539-821485 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 2/7/26 21:16, Usama Arif wrote: > >> + >> int __meminit vmemmap_populate_hvo(unsigned long addr, unsigned long end, >> int node, unsigned long headsize) >> { >> + unsigned long maddr, len, tail_pfn; >> + unsigned int order; >> pte_t *pte; >> - unsigned long maddr; >> + >> + len = end - addr; >> + order = ilog2(len * sizeof(struct page) / PAGE_SIZE); > > > This doesnt work for ARM. For len = 32 (2MB contiguous-PTE hugetlb on arm64): > ilog2(32 * 64 / 65536) = ilog2(2048 / 65536) = ilog2(0) which is undefined. HVO should not be possible for that size, and we should never reach that point, no? Remember that for HVO, the metadata must span at least two pages. -- Cheers, David