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 7775926A1AD; Fri, 16 May 2025 17:02:06 +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=1747414926; cv=none; b=UL5wv3LS1RIbo89EaqTO12ELrl+VhA9Alzw3/PLxw2fjk1sZ+6OIaTUJQuX+/oIdyte6vl7LiLeMWi9fjjalHQ1mdzZBPtsRSn+wVDqIwsQBvy9a2a1OXIZUyt1ASOOYa/rhgqUi0M7mfot70JQTPzBXfPNqjeATx4kxbiaQD2E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747414926; c=relaxed/simple; bh=cqx2+cIJWTrHCV6/oR0Yq/5mBq5YQMLp47aAmVpBt3g=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=LiczAOUnNx2tVs1MehKfSjWuXnIojggQeDtjZqydyZErbcdvsfa5P/ObXAQExG/mvdcS8N/RnzC5NT3T3d2B8oAy/ZGF0BvHXP82QDOe1PnD1+lsOKkzF1+WJpZeyUdjNRlmlAhdU16eUc1wm9AZ3QtmDKtXVg6SKGfD3MAwaL0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=lUDxZrq3; 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="lUDxZrq3" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D0EECC4CEF0; Fri, 16 May 2025 17:01:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1747414925; bh=cqx2+cIJWTrHCV6/oR0Yq/5mBq5YQMLp47aAmVpBt3g=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=lUDxZrq3AgKR6R/qdSD5KToNP2iDU/ZdgNHX0l93Wa0Usl43PM+Q69PCMJ+riC91+ GzyY7EaqkfMTyfOZpKxurTSZjkJKwfcYAJzN479Jq1XY715ZFPSbZY5p+660Pml4WJ WVrtggr77MuENEy16G/Cm6GiEnYKWR+qy9NuUFUBtEWcY2PS4Dfe2fo7FR1Ix+D4Oi 47TeVeOimVrXL3v1JgdHRttkQXduRx9X2VuGVrxf0Jjtgu8cmKYzsPNI0B6nhbhtkY it1pWXgcbOjzy34igpeFVY2tv6MHULnoGk6Vy5BS3lI1O4u50PgBdO3vKkRUd646yd GEf103TOWCZUw== Date: Fri, 16 May 2025 20:01:44 +0300 From: Mike Rapoport To: Pratyush Yadav Cc: Andrew Morton , Alexander Gordeev , Andreas Larsson , Andy Lutomirski , Ard Biesheuvel , 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 , Mark Brown , Matt Turner , Max Filippov , Michael Ellerman , Michal Simek , Palmer Dabbelt , Peter Zijlstra , Richard Weinberger , Russell King , Stafford Horne , Thomas Bogendoerfer , Thomas Gleixner , Vasily Gorbik , Vineet Gupta , Will Deacon , Praveen Kumar , 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 v2 10/13] arch, mm: set high_memory in free_area_init() Message-ID: References: <20250313135003.836600-1-rppt@kernel.org> <20250313135003.836600-11-rppt@kernel.org> Precedence: bulk X-Mailing-List: linux-csky@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: Hi Pratyush, On Fri, May 16, 2025 at 05:28:17PM +0200, Pratyush Yadav wrote: > Hi Mike, Andrew, > > On Thu, Mar 13 2025, 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. > > > > Add a generic calculation of high_memory to free_area_init() and remove > > per-architecture calculation except for the architectures that set and > > use high_memory earlier than that. > > > > Acked-by: Dave Hansen # x86 > > Signed-off-by: Mike Rapoport (Microsoft) > > --- > > arch/alpha/mm/init.c | 1 - > > arch/arc/mm/init.c | 2 -- > > arch/arm64/mm/init.c | 2 -- > > arch/csky/mm/init.c | 1 - > > arch/hexagon/mm/init.c | 6 ------ > > arch/loongarch/kernel/numa.c | 1 - > > arch/loongarch/mm/init.c | 2 -- > > arch/microblaze/mm/init.c | 2 -- > > arch/mips/mm/init.c | 2 -- > > arch/nios2/mm/init.c | 6 ------ > > arch/openrisc/mm/init.c | 2 -- > > arch/parisc/mm/init.c | 1 - > > arch/riscv/mm/init.c | 1 - > > arch/s390/mm/init.c | 2 -- > > arch/sh/mm/init.c | 7 ------- > > arch/sparc/mm/init_32.c | 1 - > > arch/sparc/mm/init_64.c | 2 -- > > arch/um/kernel/um_arch.c | 1 - > > arch/x86/kernel/setup.c | 2 -- > > arch/x86/mm/init_32.c | 3 --- > > arch/x86/mm/numa_32.c | 3 --- > > arch/xtensa/mm/init.c | 2 -- > > mm/memory.c | 8 -------- > > mm/mm_init.c | 30 ++++++++++++++++++++++++++++++ > > mm/nommu.c | 2 -- > > 25 files changed, 30 insertions(+), 62 deletions(-) > > This patch causes a BUG() when built with CONFIG_DEBUG_VIRTUAL and > passing in the cma= commandline parameter: > > ------------[ cut here ]------------ > kernel BUG at arch/x86/mm/physaddr.c:23! > ception 0x06 IP 10:ffffffff812ebbf8 error 0 cr2 0xffff88903ffff000 > CPU: 0 UID: 0 PID: 0 Comm: swapper Not tainted 6.15.0-rc6+ #231 PREEMPT(undef) > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Arch Linux 1.16.3-1-1 04/01/2014 > RIP: 0010:__phys_addr+0x58/0x60 > Code: 01 48 89 c2 48 d3 ea 48 85 d2 75 05 e9 91 52 cf 00 0f 0b 48 3d ff ff ff 1f 77 0f 48 8b 05 20 54 55 01 48 01 d0 e9 78 52 cf 00 <0f> 0b 90 0f 1f 44 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 > RSP: 0000:ffffffff82803dd8 EFLAGS: 00010006 ORIG_RAX: 0000000000000000 > RAX: 000000007fffffff RBX: 00000000ffffffff RCX: 0000000000000000 > RDX: 000000007fffffff RSI: 0000000280000000 RDI: ffffffffffffffff > RBP: ffffffff82803e68 R08: 0000000000000000 R09: 0000000000000000 > R10: ffffffff83153180 R11: ffffffff82803e48 R12: ffffffff83c9aed0 > R13: 0000000000000000 R14: 0000001040000000 R15: 0000000000000000 > FS: 0000000000000000(0000) GS:0000000000000000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: ffff88903ffff000 CR3: 0000000002838000 CR4: 00000000000000b0 > Call Trace: > > ? __cma_declare_contiguous_nid+0x6e/0x340 > ? cma_declare_contiguous_nid+0x33/0x70 > ? dma_contiguous_reserve_area+0x2f/0x70 > ? setup_arch+0x6f1/0x870 > ? start_kernel+0x52/0x4b0 > ? x86_64_start_reservations+0x29/0x30 > ? x86_64_start_kernel+0x7c/0x80 > ? common_startup_64+0x13e/0x141 > > The reason is that __cma_declare_contiguous_nid() does: > > highmem_start = __pa(high_memory - 1) + 1; > > If dma_contiguous_reserve_area() (or any other CMA declaration) is > called before free_area_init(), high_memory is uninitialized. Without > CONFIG_DEBUG_VIRTUAL, it will likely work but use the wrong value for > highmem_start. > > Among the architectures this patch touches, the below call > dma_contiguous_reserve_area() _before_ free_area_init(): > > - x86 > - s390 > - mips > - riscv > - xtensa > - loongarch > - csky For most of those this patch didn't really change anything because they initialized high_memory in mem_init() which is a part of free_area_init(). In those cases cma just did highmem_start = __pa(-1) + 1; and everyone was happy :) > The below call it _after_ free_area_init(): > - arm64 > > And the below don't call it at all: > - sparc > - nios2 > - openrisc > - hexagon > - sh > - um > - alpha > > One possible fix would be to move the calls to > dma_contiguous_reserve_area() after free_area_init(). On x86, it would > look like the diff below. The obvious downside is that moving the call > later increases the chances of allocation failure. I'm not sure how much > that actually matters, but at least on x86, that means crash kernel and > hugetlb reservations go before DMA reservation. Also, adding a patch > like that at rc7 is a bit risky. I don't think there's a risk of allocation failure, but moving things around in setup_arch() is always risky :) > The other option would be to revert this. I tried a revert, but it isn't > trivial. It runs into merge conflicts in pretty much all of the arch > files. Maybe reverting patches 11, 12, and 13 as well would make it > easier but I didn't try that. What I think we can do is to add this to mm/cma.c (not even compile tested) diff --git a/mm/cma.c b/mm/cma.c index 15632939f20a..c04be488b099 100644 --- a/mm/cma.c +++ b/mm/cma.c @@ -608,7 +608,10 @@ static int __init __cma_declare_contiguous_nid(phys_addr_t *basep, * complain. Find the boundary by adding one to the last valid * address. */ - highmem_start = __pa(high_memory - 1) + 1; + if (IS_ENABLED(CONFIG_HIGHMEM)) + highmem_start = __pa(high_memory - 1) + 1; + else + highmem_start = memblock_end_of_DRAM(); pr_debug("%s(size %pa, base %pa, limit %pa alignment %pa)\n", __func__, &size, &base, &limit, &alignment); so that highmem_start in __cma_declare_contiguous_nid() will be always correct for !HIGHMEM configs and then restore setting of highmem_start in mips::paging_init() as mips is the only architecture that actually set high_memory before free_area_init() before this patch. (for 32 bit configs of x86 there alrady a fixup d893aca973c3 ("x86/mm: restore early initialization of high_memory for 32-bits")) -- Sincerely yours, Mike.