From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B305C3C2789; Tue, 17 Mar 2026 12:47:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773751651; cv=none; b=NpcxakDIAxEcNlLtm8W/TSx+LlTKIGdZjfu5YhfK0EhfhL+sNF4GN/D7jmIsqib5hrTsf55k6G7Wb5amApbtUUMNqd9BZnxijzSynINOIAIUanjDZDlnnOlkb/rLvK5thWEdkxzWEaQ8KFDrhvmNPz7NrWBQO5AzMHLZ5an/scM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773751651; c=relaxed/simple; bh=JTwsqMb2I4dHEBP3Yr6hdh+SSfntwSOXY7WxnE4Jx3c=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=UJ4NIuem9XkWHIlt/PjaRSRpoISTTuiH4g8yRvq/gRp2qMoZ2sF6JqOCjW7EHH21dd0BEGkzCklHmSPzuay8y/oiUxH+ox7XosJ+a9KjVKpf+sgV5t+a98QyGkWcMvVDrDq54v2Ts5CGe3QnaMgl5KV8FMtq7mrEEASUh8/Uho4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Mmx0yAMP; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Mmx0yAMP" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5B404C19425; Tue, 17 Mar 2026 12:47:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1773751651; bh=JTwsqMb2I4dHEBP3Yr6hdh+SSfntwSOXY7WxnE4Jx3c=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=Mmx0yAMPyaTi+W7LMOLMl9+7j+cgfxWgN+0e8+WOHglYQuD4eGL8x36KMvnKPf8pn wVn0efCAa7oEY8R0Id09hXCEmjRworf4hb93qMp5v/xMr+uwYeFP0hoPWqXx65PWUT 28MvJwArdGTlcRdzcbOVdEVX+vwzLSPskqz2CxbZWLn4w9Lf3/9wnOrQNGE78MhC1w 8HqKB40pzPWf8MIbg3kDKy+lOBM54cmDfPUaQ8Go8LlCRvyEMOBq2etcU5lk1GT0fs /+JtdnBN9kqfbEOA1t2Fw7892WsmzlseiC2e9U/NDToOC6pX9+JrG7YzEzJ2z+7e9/ GD/Agse4pYisw== Message-ID: <169a3438-40f9-40bc-86cf-a24535494115@kernel.org> Date: Tue, 17 Mar 2026 13:47:22 +0100 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: [PATCHv7 09/18] mm/hugetlb: Defer vmemmap population for bootmem hugepages To: Kiryl Shutsemau Cc: Andrew Morton , Muchun Song , Matthew Wilcox , Usama Arif , Frank van der Linden , 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: <20260227194302.274384-1-kas@kernel.org> <20260227194302.274384-10-kas@kernel.org> <4e52f70d-e0c3-471f-8073-68c0e9bc94ca@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 3/17/26 12:28, Kiryl Shutsemau wrote: > On Mon, Mar 16, 2026 at 05:48:24PM +0100, David Hildenbrand (Arm) wrote: >> On 2/27/26 20:42, Kiryl Shutsemau (Meta) wrote: >>> Currently, the vmemmap for bootmem-allocated gigantic pages is populated >>> early in hugetlb_vmemmap_init_early(). However, the zone information is >>> only available after zones are initialized. If it is later discovered >>> that a page spans multiple zones, the HVO mapping must be undone and >>> replaced with a normal mapping using vmemmap_undo_hvo(). >>> >>> Defer the actual vmemmap population to hugetlb_vmemmap_init_late(). At >>> this stage, zones are already initialized, so it can be checked if the >>> page is valid for HVO before deciding how to populate the vmemmap. >>> >>> This allows us to remove vmemmap_undo_hvo() and the complex logic >>> required to rollback HVO mappings. >>> >>> In hugetlb_vmemmap_init_late(), if HVO population fails or if the zones >>> are invalid, fall back to a normal vmemmap population. >>> >>> Postponing population until hugetlb_vmemmap_init_late() also makes zone >>> information available from within vmemmap_populate_hvo(). >> >> So we'll keep marking the sections as SECTION_IS_VMEMMAP_PREINIT such >> that sparse_init_nid() will still properly skip it and leave population >> to hugetlb_vmemmap_init_late(). >> >> Should we clear SECTION_IS_VMEMMAP_PREINIT in case we run into the >> hugetlb_bootmem_page_zones_valid() scenario? >> >> I suspect we don't care about SECTION_IS_VMEMMAP_PREINIT after boot and >> can just leave the flag set. (maybe we wan to add a comment in the code? >> above the vmemmap_populate() ?) > > I think keeping the flag is right thing to do. > > SECTION_IS_VMEMMAP_PREINIT indicates to core-sparse that the section > should not be populated and it will be initialized elsewhere. Even in > !hugetlb_bootmem_page_zones_valid() we take care of it in > hugetlb_vmemmap_init_late(). Makes sense. -- Cheers, David