From nobody Mon Feb 9 04:45:18 2026 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 8FD1612CD96; Wed, 16 Apr 2025 08:17:04 +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=1744791426; cv=none; b=OdkKNIz5IAjHKsQI90bxVHlo9kMaI0Dd4FVd8uu3oHO5d3Cd77AhhR65h3pzMH9D6meketwXsJMIHuV2UhcE2cb2TuTZIxfpIbSuqHjbRVKSnVPwc5/WWjGsw7p/+TGxecUe8CuhCorpNP9A1KHCOZtIRr4jcgyKpBt3UBUiY8w= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744791426; c=relaxed/simple; bh=u4CrPtjM2/s1r9RucEkw3Wm4tDwvpmG49jCjfS2ABJU=; h=Date:From:To:Subject:Cc:In-Reply-To:References:MIME-Version: Message-ID:Content-Type; b=MH8p4ESN8SIhnSMYYGsy0lF1sq2vdLxRDd+ZCmtvNwXslhjJ2IB+9G+aE3RZjDinvuN4eYSHGyZ1h0qn7noOL7EarvIimjYmj1SVcyzL2XKhM1g3jNlUSFSHNDNCn786kC6ffaBkQIlnNvGO8PLcDoIw+dqBlbPcHKebdHgpKL8= 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=v6bfIxnb; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=fsGZGUhy; 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="v6bfIxnb"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="fsGZGUhy" Date: Wed, 16 Apr 2025 08:16:55 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1744791422; 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=dV4c1nIHek6fWfDNR/sFsg7UIs5ti7koym3h3PZsGbw=; b=v6bfIxnbAk7i8S5SMwW7Og0gKrF5n3pyXD1KzLTb7+EumBi8cZAa7arvpDlFlcCVA623cg Mvw66sX/2YVwMNnaEICsa4PqvswKPNjMtJ41b+dzy47gq6GZGjqVsmlRneSF9W+DlMokdg k6ihkoqXViBEXU+Lhvcqn8/TwlIXWjtCMTPrVKpDy197vsQd2X57mzI+WlmgqzL5b6Pyyi aW+I6Xol6WHfMu34N/7og9ebl7xOUpXBOPtd61N/cDIBON42m3BjVW2M+Lg4EiQSdTM6nK IMdJv+hwAAomScG14yWubZQNEmWT7XGuNdgv7fHmMp6AysUwt3O2nxSwAz+p8Q== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1744791422; 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=dV4c1nIHek6fWfDNR/sFsg7UIs5ti7koym3h3PZsGbw=; b=fsGZGUhyiSHYQEFk7thnNeW+JNl6ZqS1MtdUvvxJBhC27V27BN/xJw4c4nsrK+yLjOMFaq 3Mfrf+oUUEEAh4Dw== 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> References: <20250413080858.743221-1-rppt@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-ID: <174479141543.31282.1765445425938242082.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: 1e07b9fad022e0e02215150ca1e20912e78e8ec1 Gitweb: https://git.kernel.org/tip/1e07b9fad022e0e02215150ca1e20912e= 78e8ec1 Author: Mike Rapoport (Microsoft) AuthorDate: Sun, 13 Apr 2025 11:08:58 +03:00 Committer: Ingo Molnar CommitterDate: Wed, 16 Apr 2025 09:51:02 +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. [ mingo: Fixed build failure. ] Fixes: 6faea3422e3b ("arch, mm: streamline HIGHMEM freeing") Reported-by: Dave Hansen Tested-by: Arnd Bergmann Tested-by: Dave Hansen Signed-off-by: Mike Rapoport (Microsoft) Signed-off-by: Ingo Molnar Acked-by: Dave Hansen 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 --- 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..2f38175 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 +#ifdef CONFIG_X86_32 + /* + * Discard memory above 4GB because 32-bit systems are limited to 4GB + * of memory even with HIGHMEM. + */ + memblock_remove(PFN_PHYS(MAX_NONPAE_PFN), -1); +#endif + /* Throw away partial pages: */ memblock_trim_memory(PAGE_SIZE);