From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 85B25D2FECD for ; Tue, 27 Jan 2026 18:11:42 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 5C7546B0088; Tue, 27 Jan 2026 13:11:41 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 574966B0089; Tue, 27 Jan 2026 13:11:41 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 455816B008A; Tue, 27 Jan 2026 13:11:41 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 33EC16B0088 for ; Tue, 27 Jan 2026 13:11:41 -0500 (EST) Received: from smtpin12.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 99906C182E for ; Tue, 27 Jan 2026 18:11:40 +0000 (UTC) X-FDA: 84378536760.12.1FED591 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf27.hostedemail.com (Postfix) with ESMTP id 12A8040016 for ; Tue, 27 Jan 2026 18:11:38 +0000 (UTC) Authentication-Results: imf27.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=ByaWjtsS; spf=pass (imf27.hostedemail.com: domain of rppt@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=rppt@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1769537499; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=2GTgDTMSjRtu9XA/FLPKOljq2ml0hMhzhLI6yqYD4CI=; b=EFb9qxQUV3czWI3Y+abwyULuvLxNnwWcSU1jJcX8Q+sGUzIDHwbgt7U08WiRO8ZGOMBkul awfNCx61DSrlU1nZT1OTQDfCxpiioXZnDOmQRkk2iRTzbwKwT4leWYjVmQe+zcmr8CpIV5 J0I9KODb8Ij1dFybDhVtdXsjU4xVcIw= ARC-Authentication-Results: i=1; imf27.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=ByaWjtsS; spf=pass (imf27.hostedemail.com: domain of rppt@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=rppt@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1769537499; a=rsa-sha256; cv=none; b=X+opd8ByNKvaiF09HJiFEhdAZ2aUfzqTd4+x7Gkl/QGMR90SZqeclWmou4dzVGzAZHWmuG 1RiBEE7dckmCqbpc2ziqqhQG4Qaj5gkCQx70fP/fUoG6vUWSCCc2dkkBojDrBOUJxOveF9 wu4c8KtqgABRvd/lo/Bd0buEYvVVRF0= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 503606013B; Tue, 27 Jan 2026 18:11:38 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id BB4A5C116C6; Tue, 27 Jan 2026 18:11:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1769537498; bh=esR6CFIdT2IldE04x541sMjzg2hM0kwiBu50M1Q4i6U=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ByaWjtsSvwoLSW/kNH7xWLyVjxxz5GlRC8jYXsgV/gqb4/lcnR/DbPtvL6ZsfFpSk UMuJqyvtKtohQKsmQxoM99rDtG1O4GqRTw9ZhQsEmWLSfLiBrUcxYInGfM89HyeRgM CxuZITcoVajun6fKU8J38DnbH8BoWcjGzNDWtXdHngn0Bx8YWSVtKYdo5/nJpd1YVl JH22ZwPPk16pgnbMx9Vr3rouzXVb84WvDBKXKk6PK90HPv2OIOvHU6AimhWntYIXkX +GnE9E9QwmWlr81X+KXfieSH8beDfJtCHQfJLkjpSxZ2STIQw2Fz3NkhSNYKoguw1h QmmKWVv1yE1UQ== Date: Tue, 27 Jan 2026 20:11:19 +0200 From: Mike Rapoport To: Andreas Larsson Cc: Andrew Morton , Borislav Petkov , Brian Cain , Catalin Marinas , "David S. Miller" , Dave Hansen , David Hildenbrand , Dinh Nguyen , Geert Uytterhoeven , Guo Ren , Helge Deller , Huacai Chen , Ingo Molnar , Johannes Berg , John Paul Adrian Glaubitz , "Liam R. Howlett" , Lorenzo Stoakes , Madhavan Srinivasan , Magnus Lindholm , Matt Turner , Max Filippov , Michael Ellerman , Michal Hocko , Michal Simek , Palmer Dabbelt , Richard Weinberger , Russell King , Stafford Horne , Suren Baghdasaryan , Thomas Gleixner , Vineet Gupta , Vlastimil Babka , Will Deacon , linux-alpha@vger.kernel.org, linux-kernel@vger.kernel.org, linux-snps-arc@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-csky@vger.kernel.org, linux-hexagon@vger.kernel.org, loongarch@lists.linux.dev, linux-m68k@lists.linux-m68k.org, linux-openrisc@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-um@lists.infradead.org, linux-mm@kvack.org, x86@kernel.org Subject: Re: [PATCH mm-unstable] arch, mm: consolidate empty_zero_page Message-ID: References: <20260124095628.668870-1-rppt@kernel.org> <2157220c-0394-40fa-9918-a8514171bd10@gaisler.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2157220c-0394-40fa-9918-a8514171bd10@gaisler.com> X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 12A8040016 X-Stat-Signature: khxst6ie8phgxku5xxwabptz8y5nhjss X-Rspam-User: X-HE-Tag: 1769537498-878693 X-HE-Meta: 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 5Qbi/8gq 0quUJ 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: Hi, On Tue, Jan 27, 2026 at 05:02:39PM +0100, Andreas Larsson wrote: > On 2026-01-24 10:56, Mike Rapoport wrote: > > > Every architecture defines empty_zero_page that way or another, but for the > > most of them it is always a page aligned page in BSS and most definitions > > of ZERO_PAGE do virt_to_page(empty_zero_page). > > Running this in an LDOM on an UltraSparc T4 sparc64, the entire LDOM > hangs after a while during boot. > > > diff --git a/arch/sparc/mm/init_64.c b/arch/sparc/mm/init_64.c > > index c2d19c9a9244..2bd99944176d 100644 > > --- a/arch/sparc/mm/init_64.c > > +++ b/arch/sparc/mm/init_64.c > > @@ -177,9 +177,6 @@ extern unsigned long sparc_ramdisk_image64; > > extern unsigned int sparc_ramdisk_image; > > extern unsigned int sparc_ramdisk_size; > > > > -struct page *mem_map_zero __read_mostly; > > -EXPORT_SYMBOL(mem_map_zero); > > - > > unsigned int sparc64_highest_unlocked_tlb_ent __read_mostly; > > > > unsigned long sparc64_kern_pri_context __read_mostly; > > @@ -2506,18 +2503,6 @@ void __init mem_init(void) > > */ > > register_page_bootmem_info(); > > > > - /* > > - * Set up the zero page, mark it reserved, so that page count > > - * is not manipulated when freeing the page from user ptes. > > - */ > > - mem_map_zero = alloc_pages(GFP_KERNEL|__GFP_ZERO, 0); > > - if (mem_map_zero == NULL) { > > - prom_printf("paging_init: Cannot alloc zero page.\n"); > > - prom_halt(); > > - } > > - mark_page_reserved(mem_map_zero); > > - > > - > > if (tlb_type == cheetah || tlb_type == cheetah_plus) > > cheetah_ecache_flush_init(); > > } > > This just removes the mark_page_reserved(mem_map_zero) without > replacing it with something corresponding to that. Perhaps part > of the problem? I don't think so, empty_zero_page is in BSS now an it's reserved as a part of the kernel image. I suspect that virt_to_page() does not work BSS symbols on sparc64. Can you please try with this patch: diff --git a/arch/sparc/include/asm/pgtable_64.h b/arch/sparc/include/asm/pgtable_64.h index 74ede706fb32..0578c5172d4e 100644 --- a/arch/sparc/include/asm/pgtable_64.h +++ b/arch/sparc/include/asm/pgtable_64.h @@ -22,6 +22,7 @@ #include #include #include +#include /* The kernel image occupies 0x4000000 to 0x6000000 (4MB --> 96MB). * The page copy blockops can use 0x6000000 to 0x8000000. @@ -210,6 +211,11 @@ extern unsigned long _PAGE_CACHE; extern unsigned long pg_iobits; extern unsigned long _PAGE_ALL_SZ_BITS; +extern unsigned long kern_base; +#define ZERO_PAGE(vaddr) \ + (virt_to_page(empty_zero_page + ((unsigned long)__va(kern_base)) - \ + ((unsigned long)KERNBASE))) + /* PFNs are real physical page numbers. However, mem_map only begins to record * per-page information starting at pfn_base. This is to handle systems where * the first physical page in the machine is at some huge physical address, diff --git a/arch/sparc/mm/init_64.c b/arch/sparc/mm/init_64.c index 2bd99944176d..d2d724ba4f83 100644 --- a/arch/sparc/mm/init_64.c +++ b/arch/sparc/mm/init_64.c @@ -170,6 +170,8 @@ static void __init read_obp_memory(const char *property, /* Kernel physical address base and size in bytes. */ unsigned long kern_base __read_mostly; +EXPORT_SYMBOL(kern_base); + unsigned long kern_size __read_mostly; /* Initial ramdisk setup */ > Cheers, > Andreas -- Sincerely yours, Mike.