From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 AC2231DF73A for ; Sat, 18 Jul 2026 02:23:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784341436; cv=none; b=gEqTrG/NcZhffomflflF95s256g1r2wZmgzTxcTY85W9PTauKtytz7hXUtNST2kCKViIu6BjVnepX2sQMPbRmvUhoUf/BqDM/pKBiNJhvE9BscbvA4123p2BMLu1Gv/p9ZafImiTYdxNzIreXkzMxFtjFBglozcHqfcg1DWhun4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784341436; c=relaxed/simple; bh=V631OEw6ZF4wowvNOyXSGNMC9eXJGp9MukitYLaZUTY=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=lya1PPzRlADMA9MGPfBB6gnl3g8bvQe92at2zo4b24wp6FOnbx44X6P+5yoizhPt+JdDu0r0lG7/0NQIuKTR1Zx9VIeULJ/eTzNkZhPMfNHSiRxzhPVQJ+ityVmAH1UmCColeLYOU6rSmWs8z+bbyBIJA3nkMUwarol5XmdAo6A= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=qq65hb0S; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="qq65hb0S" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9F2D81F000E9; Sat, 18 Jul 2026 02:23:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1784341435; bh=iQ/Yf7wVnFQB+IHSZULMU8+KgGXBXMuHZZzMw8HGnT0=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=qq65hb0S0liK/slomG4DFDFnkLSsN81uHm/Ra4fwu8UvpcI9Mwxck8gwrLG1l/XuI ScCKZpN3gWmZwuORrLBh/IY6L+g8Jx3/js0HYQ9ZGYgpKmFeJOOuwvwhDFeZPetdK7 2hqYr/OcRIOofpgk5ZBh7PW80cAQ/Przn13h2cHI= Date: Fri, 17 Jul 2026 19:23:54 -0700 From: Andrew Morton To: Jiakai Xu Cc: linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, David Hildenbrand , Guo Ren , Mike Rapoport , Vishal Moola , Albert Ou , Alexandre Ghiti , Junhui Liu , Kiryl Shutsemau , Muchun Song , Nam Cao , Palmer Dabbelt , Paul Walmsley , Vivian Wang Subject: Re: [PATCH] riscv/mm: use physical alignment for vmemmap_start_pfn Message-Id: <20260717192354.045ed96b3f67e78b00a0319d@linux-foundation.org> In-Reply-To: <20260716115326.3466926-1-xujiakai2025@iscas.ac.cn> References: <20260716115326.3466926-1-xujiakai2025@iscas.ac.cn> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Thu, 16 Jul 2026 11:53:25 +0000 Jiakai Xu wrote: > RISC-V computes vmemmap_start_pfn by rounding phys_ram_base down to > VMEMMAP_ADDR_ALIGN. That alignment must therefore be expressed in the > physical-address domain. > > Commit 476849b0fba4 ("riscv/mm: align vmemmap to maximal folio size") > attempted to account for the maximal folio alignment by feeding > MAX_FOLIO_VMEMMAP_ALIGN directly into VMEMMAP_ADDR_ALIGN. However, > MAX_FOLIO_VMEMMAP_ALIGN is measured in bytes of struct page storage, > whereas VMEMMAP_ADDR_ALIGN is used to align a physical address. > > The mask-based compound_info encoding requires pfn_to_page(0) to be > naturally aligned to MAX_FOLIO_VMEMMAP_ALIGN. Commit 9f94db4c7eaa > ("mm/sparse: check memmap alignment for compound_info_has_mask()") > added a check for that requirement and exposed the unit mismatch on > systems such as QEMU virt, where the DRAM base is not aligned to > MAX_FOLIO_NR_PAGES * PAGE_SIZE. > > Convert MAX_FOLIO_VMEMMAP_ALIGN to the equivalent physical alignment > before using it in VMEMMAP_ADDR_ALIGN. This keeps the existing > round_down() logic while making the resulting vmemmap base satisfy the > mask-alignment requirement. Thanks. > Fixes: 476849b0fba4 ("riscv/mm: align vmemmap to maximal folio size") That's in 7.1, so I'll add a cc:stable to help ensure this gets backported. The changelog doesn't tell people *why* we're proposing a backport - to understand that we should tell them how the bug affects users. So I'll paste your following boot-time warning messages into the changelog. > --- a/arch/riscv/mm/init.c > +++ b/arch/riscv/mm/init.c > @@ -63,7 +63,8 @@ EXPORT_SYMBOL(phys_ram_base); > > #ifdef CONFIG_SPARSEMEM_VMEMMAP > #define VMEMMAP_ADDR_ALIGN max(1ULL << SECTION_SIZE_BITS, \ > - MAX_FOLIO_VMEMMAP_ALIGN) > + PFN_PHYS(MAX_FOLIO_VMEMMAP_ALIGN / \ > + sizeof(struct page))) > > unsigned long vmemmap_start_pfn __ro_after_init; > EXPORT_SYMBOL(vmemmap_start_pfn); I'll queue this as a backportable hotfix and shall await reviewer input (please).