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([2a02:6b6f:e752:9400:18cf:c773:ee86:c436]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4362972fc1bsm16866971f8f.28.2026.02.07.14.50.48 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 07 Feb 2026 14:50:48 -0800 (PST) Message-ID: <110aedf7-9f31-4552-b772-395433d7bdb3@gmail.com> Date: Sat, 7 Feb 2026 22:50:47 +0000 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: [PATCHv6 11/17] mm/hugetlb: Remove fake head pages Content-Language: en-GB To: "David Hildenbrand (Arm)" , 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> <412359f2-ecfb-498a-9717-f0a442abd3f7@kernel.org> From: Usama Arif In-Reply-To: <412359f2-ecfb-498a-9717-f0a442abd3f7@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 07/02/2026 21:25, David Hildenbrand (Arm) wrote: > 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. > Ah yeah thats right, ignore me. Its also checked in hugetlb_vmemmap_optimizable_size, so its all good.