From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) (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 DD2881E51F1 for ; Wed, 12 Mar 2025 06:35:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=139.178.84.217 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741761322; cv=none; b=UQgMBvHmDPzhgaxCV4Sxb0eAu0odxrJgMoxGlGN4nN7VIbRIdQ5Dn053NpQbdNxT0GwXHuA5/M7fhcKv/LuYFegFrnd9kmInWWbuT3jLI7MDahi7pcC+8GBD96iy8uADqGWNcsJLpAU/oXpuHzEEbMUWWNC+5vIX2kXRIJrlqv0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741761322; c=relaxed/simple; bh=5mdaPZVI9H0/LV5hmobVgKrUIL2iuMSKhSTxPs81fPU=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=DU1XbMGkd2zoyPQEHnkrXxtPkTVmGkq828KkJJ8np3M0MP5fOKyRuGGB4mErU4MGg69NnuGK76g4LEOtMgEsMYLZ1guvzgsWFq+vu0+zq1g276pa1alAbx9i7oomjQxgXZRPRwLEHndLwdo/fuUln5DJMNNNf5oU2fYLOIbjtgw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=kernel.org; spf=pass smtp.mailfrom=kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=s5OTgyGp; arc=none smtp.client-ip=139.178.84.217 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=kernel.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=kernel.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="s5OTgyGp" Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by dfw.source.kernel.org (Postfix) with ESMTP id A9EFC5C47AF; Wed, 12 Mar 2025 06:33:02 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 407D8C4CEE3; Wed, 12 Mar 2025 06:35:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1741761319; bh=5mdaPZVI9H0/LV5hmobVgKrUIL2iuMSKhSTxPs81fPU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=s5OTgyGpaumshikTp+iDDuLZlaDN5ZFNt0xhyxhEjxDoGdrRr5fCFJqupGsQ1e9mc x5+ujh1N69RbM6sMUkTLS3DxQMtFw4J494229H1wYU5SpwxEIdYz9MdPy8mIFSl7pw l37VuFqhXXoOyw7aw+nwsTVBrmtEviGrZHfYnDThjgKfYUlSm8F0VvgI37TsJEXPQg Z/TS0S2P3vKV4E8YK2hLZIT0IUPWeSPBaDZrgP63fW1/ioeooSw+E437KEQCfrER7m 3bE2KZoye8/AcR9u24hQHDyQiTnD+Psif0K5SR2GQnCkTLYx0lBk09w8YpbQLP/phf PvVxVGjqV5khg== Date: Wed, 12 Mar 2025 08:34:56 +0200 From: Mike Rapoport To: "Russell King (Oracle)" Cc: Mark Brown , Andrew Morton , Alexander Gordeev , Andreas Larsson , Andy Lutomirski , Arnd Bergmann , Borislav Petkov , Brian Cain , Catalin Marinas , Dave Hansen , "David S. Miller" , Dinh Nguyen , Geert Uytterhoeven , Gerald Schaefer , Guo Ren , Heiko Carstens , Helge Deller , Huacai Chen , Ingo Molnar , Jiaxun Yang , Johannes Berg , John Paul Adrian Glaubitz , Madhavan Srinivasan , Matt Turner , Max Filippov , Michael Ellerman , Michal Simek , Palmer Dabbelt , Peter Zijlstra , Richard Weinberger , Stafford Horne , Thomas Bogendoerfer , Thomas Gleixner , Vasily Gorbik , Vineet Gupta , 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-mips@vger.kernel.org, linux-openrisc@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-um@lists.infradead.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org Subject: Re: [PATCH 10/13] arch, mm: set high_memory in free_area_init() Message-ID: References: <20250306185124.3147510-1-rppt@kernel.org> <20250306185124.3147510-11-rppt@kernel.org> Precedence: bulk X-Mailing-List: linux-m68k@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: On Tue, Mar 11, 2025 at 09:59:32PM +0000, Russell King (Oracle) wrote: > On Tue, Mar 11, 2025 at 05:51:06PM +0000, Mark Brown wrote: > > On Thu, Mar 06, 2025 at 08:51:20PM +0200, Mike Rapoport wrote: > > > From: "Mike Rapoport (Microsoft)" > > > > > > high_memory defines upper bound on the directly mapped memory. > > > This bound is defined by the beginning of ZONE_HIGHMEM when a system has > > > high memory and by the end of memory otherwise. > > > > > > All this is known to generic memory management initialization code that > > > can set high_memory while initializing core mm structures. > > > > > > Remove per-architecture calculation of high_memory and add a generic > > > version to free_area_init(). > > > > This patch appears to be causing breakage on a number of 32 bit arm > > platforms, including qemu's virt-2.11,gic-version=3. Affected platforms > > die on boot with no output, a bisect with qemu points at this commit and > > those for physical platforms appear to be converging on the same place. > > I'm not convinced that the old and the new code is doing the same > thing. > > The new code: > > + phys_addr_t highmem = memblock_end_of_DRAM(); > + > +#ifdef CONFIG_HIGHMEM > + unsigned long pfn = arch_zone_lowest_possible_pfn[ZONE_HIGHMEM]; > + > + if (arch_has_descending_max_zone_pfns() || highmem > PFN_PHYS(pfn)) > + highmem = PFN_PHYS(pfn); > +#endif > + > + high_memory = phys_to_virt(highmem - 1) + 1; > > First, when CONFIG_HIGHMEM is disabled, this code assumes that the last > byte of DRAM declared to memblock is the highmem limit. This _could_ > overflow phys_to_virt() and lead to an invalid value for high_memory. > > Second, arch_zone_lowest_possible_pfn[ZONE_HIGHMEM] is the _start_ of > highmem. This is not what arch code sets high_memory to - because > the start of highmem may not contiguously follow on from lowmem. > > In arch/arm/mm/mmu.c, lowmem_limit is computed to be the highest + 1 > physical address that lowmem can possibly be, taking into account the > amount of vmalloc memory that is required. This is used to set > high_memory. > > We also limit the amount of usable RAM via memblock_set_current_limit() > which memblock_end_of_DRAM() doesn't respect. > > I don't think the proposed generic version is suitable for 32-bit arm. Unless I'm missing something, both memblock.current_limit and start of ZONE_HIGHMEM are set to arm_lowmem_limit which will be different from memblock_end_of_DRAM() only for machines with more than nearly 4GiB of RAM and those will supposedly use HIGHMEM anyway. But this does not matter anyway because failures Mark reported happen because 32-bit arm uses high_memory before mem_init() and that what causes the hangs. Here's the fix I have, I'll send v2 shortly. diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c index e492d58a0386..f02f872ea8a9 100644 --- a/arch/arm/mm/mmu.c +++ b/arch/arm/mm/mmu.c @@ -1250,6 +1250,8 @@ void __init adjust_lowmem_bounds(void) arm_lowmem_limit = lowmem_limit; + high_memory = __va(arm_lowmem_limit - 1) + 1; + if (!memblock_limit) memblock_limit = arm_lowmem_limit; diff --git a/arch/arm/mm/nommu.c b/arch/arm/mm/nommu.c index 65903ed5e80d..1a8f6914ee59 100644 --- a/arch/arm/mm/nommu.c +++ b/arch/arm/mm/nommu.c @@ -146,6 +146,7 @@ void __init adjust_lowmem_bounds(void) phys_addr_t end; adjust_lowmem_bounds_mpu(); end = memblock_end_of_DRAM(); + high_memory = __va(end - 1) + 1; memblock_set_current_limit(end); } diff --git a/mm/mm_init.c b/mm/mm_init.c index 545e11f1a3ba..0aef4bef93c4 100644 --- a/mm/mm_init.c +++ b/mm/mm_init.c @@ -1765,14 +1765,20 @@ static bool arch_has_descending_max_zone_pfns(void) static void set_high_memory(void) { + unsigned long pfn = arch_zone_lowest_possible_pfn[ZONE_HIGHMEM]; phys_addr_t highmem = memblock_end_of_DRAM(); -#ifdef CONFIG_HIGHMEM - unsigned long pfn = arch_zone_lowest_possible_pfn[ZONE_HIGHMEM]; + /* + * Some architectures (e.g. ARM) set high_memory very early and + * use it in arch setup code. + * If an architecture already set high_memory don't overwrite it + */ + if (high_memory) + return; - if (arch_has_descending_max_zone_pfns() || highmem > PFN_PHYS(pfn)) + if (IS_ENABLED(CONFIG_HIGHMEM) && + (arch_has_descending_max_zone_pfns() || highmem > PFN_PHYS(pfn))) highmem = PFN_PHYS(pfn); -#endif high_memory = phys_to_virt(highmem - 1) + 1; } -- Sincerely yours, Mike.