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 600FF191484; Tue, 27 Jan 2026 18:11:38 +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=1769537498; cv=none; b=bom0NsDwjy3OAAPnEYc6HgxaDiteP6cVsyjOFaqR301ug7JVsmrOW+FpyLEzmQFPtqOR1rGZtP7IXBELM2XuHBa38vpkJxUAQMRR1HmqQhpNfXu9E+Ofn21NcKhwvSdBKdqkXguB8sEITd8zgJQYx1hQNInCiGuS+K+EUFhYnrU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769537498; c=relaxed/simple; bh=esR6CFIdT2IldE04x541sMjzg2hM0kwiBu50M1Q4i6U=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=JKYKnJI1aU7my69d+SKLZIwbuXM+tqKtWT6eqIJXJLo5+T1t80BZMH3NEFeZGnRLyX8UCm06eKWgnEOVshB56Qy9KG15PcfBvmunCb307d80LbMKHhoylEc5qzqgeaj9iGlLZrVzOppFDQ7SoW//QfvApm4ZBZ4AoDKYtZGxJsI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ByaWjtsS; 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="ByaWjtsS" 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> 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-Disposition: inline In-Reply-To: <2157220c-0394-40fa-9918-a8514171bd10@gaisler.com> 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.