From nobody Sun Dec 14 12:16:11 2025 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (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 281AA1E884; Sat, 19 Apr 2025 15:01:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745074882; cv=none; b=RKGkN5HHEdXPezbIEyv62sr0+2OI3keiHI2mNxB2v7zqtc6OZk/noj1YU9NjXiCpToHrF3sUEAO/TsaAQdwtr++qF4d8EbwX2326NDatWfGt8N4PmhSbpRSovDh90we5UTLORVYJaP7vEgl75pe+CdPdq9PD55UdgrDDwHsStpM= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745074882; c=relaxed/simple; bh=YgVYSHeKY/a1W/bRGfnFAmUq6gV1z1GAnooUQz1ZYic=; h=Date:From:To:Subject:Cc:In-Reply-To:References:MIME-Version: Message-ID:Content-Type; b=pja+s3IGm994LAcbH40dTY26YNV/49XRDIUiavLz8R8BicafZkIIZ4mM1HvJqqkJzBsbxSZr+imatqB347y7EQSrND1QAQINn+J/Xz5EwzGmlJbDRb7jQ4CAVVxLD5zxajWEpUb9dV7NQ66W9xDr/2zX9eHVnj9XoyNDJzIgcrA= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=Jbg1EhHe; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=qoO/JRDB; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="Jbg1EhHe"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="qoO/JRDB" Date: Sat, 19 Apr 2025 15:00:31 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1745074868; h=from:from:sender:sender:reply-to: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:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Y1M1aCK5ESLtJp6YPPmUCNmlhTn4cy5InXXOaZ8RKfo=; b=Jbg1EhHe0Mew6MM62uWjy8l3S/MSG6gxdeWU0cITOlS2rKBJgRj0FxtFvBJBhCW2kXwTYp 9bfHvDmfNYCffB6CqGcoJogB6u8bK3M6TBveSTheFFprEDFOGfahevPy+mIDlrbrYKwFj1 yjtXxdM1NcEn7j+JwdZmixleUwPTl+n4MpUvywOoLva2A032VFtwAfsR/vwXuSnt4BmS0Q ABbWJEDAbjRr/uWRSDjYf+Rt2Eh4OJ7H4T5KSxhsSBUJby0wm92SIIG0qwaLcOz0fus8ec bJQ9FOXSFtFQd0u2Bpryb/IxE2Tu1yx601sns5MPuYd0bv8FZjGSrS5MNATr/Q== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1745074868; h=from:from:sender:sender:reply-to: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:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Y1M1aCK5ESLtJp6YPPmUCNmlhTn4cy5InXXOaZ8RKfo=; b=qoO/JRDBqt/fRZuv3OiKh8fbSnNgnx80Yxlg83Dh8LWLLi3G5S5WMJOYhwRY3UIJgG+KdX 6dv+zG2NDjCEU/DQ== From: "tip-bot2 for Mike Rapoport (Microsoft)" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: x86/urgent] x86/e820: Discard high memory that can't be addressed by 32-bit systems Cc: Dave Hansen , Arnd Bergmann , "Mike Rapoport (Microsoft)" , Ingo Molnar , Andy Shevchenko , Arnd Bergmann , Davide Ciminaghi , "H. Peter Anvin" , Linus Torvalds , Matthew Wilcox , Paolo Bonzini , Sean Christopherson , kvm@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20250413080858.743221-1-rppt@kernel.org # discussion and submission> References: <20250413080858.743221-1-rppt@kernel.org # discussion and submission> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-ID: <174507483228.31282.2105701735501523134.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Precedence: bulk Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable The following commit has been merged into the x86/urgent branch of tip: Commit-ID: 83b2d345e1786fdab96fc2b52942eebde125e7cd Gitweb: https://git.kernel.org/tip/83b2d345e1786fdab96fc2b52942eebde= 125e7cd Author: Mike Rapoport (Microsoft) AuthorDate: Sun, 13 Apr 2025 11:08:58 +03:00 Committer: Ingo Molnar CommitterDate: Sat, 19 Apr 2025 16:48:18 +02:00 x86/e820: Discard high memory that can't be addressed by 32-bit systems Dave Hansen reports the following crash on a 32-bit system with CONFIG_HIGHMEM=3Dy and CONFIG_X86_PAE=3Dy: > 0xf75fe000 is the mem_map[] entry for the first page >4GB. It > obviously wasn't allocated, thus the oops. BUG: unable to handle page fault for address: f75fe000 #PF: supervisor write access in kernel mode #PF: error_code(0x0002) - not-present page *pdpt =3D 0000000002da2001 *pde =3D 000000000300c067 *pte =3D 00000000000= 00000 Oops: Oops: 0002 [#1] SMP NOPTI CPU: 0 UID: 0 PID: 0 Comm: swapper Not tainted 6.15.0-rc1-00288-ge618ee89= 561b-dirty #311 PREEMPT(undef) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/0= 1/2014 EIP: __free_pages_core+0x3c/0x74 ... Call Trace: memblock_free_pages+0x11/0x2c memblock_free_all+0x2ce/0x3a0 mm_core_init+0xf5/0x320 start_kernel+0x296/0x79c i386_start_kernel+0xad/0xb0 startup_32_smp+0x151/0x154 The mem_map[] is allocated up to the end of ZONE_HIGHMEM which is defined by max_pfn. The bug was introduced by this recent commit: 6faea3422e3b ("arch, mm: streamline HIGHMEM freeing") Previously, freeing of high memory was also clamped to the end of ZONE_HIGHMEM but after this change, memblock_free_all() tries to free memory above the of ZONE_HIGHMEM as well and that causes access to mem_map[] entries beyond the end of the memory map. To fix this, discard the memory after max_pfn from memblock on 32-bit systems so that core MM would be aware only of actually usable memory. Fixes: 6faea3422e3b ("arch, mm: streamline HIGHMEM freeing") Reported-by: Dave Hansen Tested-by: Arnd Bergmann Signed-off-by: Mike Rapoport (Microsoft) Signed-off-by: Ingo Molnar Cc: Andy Shevchenko Cc: Arnd Bergmann Cc: Davide Ciminaghi Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Matthew Wilcox Cc: Paolo Bonzini Cc: Sean Christopherson Cc: kvm@vger.kernel.org Link: https://lore.kernel.org/r/20250413080858.743221-1-rppt@kernel.org # d= iscussion and submission --- arch/x86/kernel/e820.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c index 9d8dd8d..9920122 100644 --- a/arch/x86/kernel/e820.c +++ b/arch/x86/kernel/e820.c @@ -1299,6 +1299,14 @@ void __init e820__memblock_setup(void) memblock_add(entry->addr, entry->size); } =20 + /* + * 32-bit systems are limited to 4BG of memory even with HIGHMEM and + * to even less without it. + * Discard memory after max_pfn - the actual limit detected at runtime. + */ + if (IS_ENABLED(CONFIG_X86_32)) + memblock_remove(PFN_PHYS(max_pfn), -1); + /* Throw away partial pages: */ memblock_trim_memory(PAGE_SIZE);