From nobody Sat Sep 26 14:39:43 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 5FE433F1AAD; Mon, 31 Aug 2026 17:35:38 +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=1788197739; cv=none; b=XVoReEV3AIAoFhnv4nBKO3RT1oGph9TI5NmOCu/9dxxOvYoqrgFWzcx06b9D3V1dTgMFHsO4Lvp2e+fXcVUHWUilxvrsOzUcJ78IcbOVNf0SEYstjpLa7/0oRzHax5Jp4uai2Pp3MT3nRanaQgplRY3goQXo8Baroz1HrU54hwg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788197739; c=relaxed/simple; bh=2qVC5yoQBquWe6LLwPrlx9oakMBqorOlsrR2KF1e3Jc=; h=Date:From:To:Subject:Cc:In-Reply-To:References:MIME-Version: Message-ID:Content-Type; b=dvFlnbV3MGsOVum3rEpciZR0EIDxzvFbmxi761nSxRYk8kl8yLEDoXI8AjTh/XlGIym/Q/hvAZ/MTKmaMYsf8P8qnXa7dB+YhWRWhnfKQ0ObAxMbGpv6DwwNcvQfXREe4xKhbyvOdClXheuy0XhOdEfFCqR53RnrcijwDAJMCkU= 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=qJPoO2d9; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=uAUN7GQ2; 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="qJPoO2d9"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="uAUN7GQ2" Date: Mon, 31 Aug 2026 17:35:34 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1788197736; 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=n8Dx2ZMejgOo8yw+tVY8+elR2md2Nj5Pg4EyNxccHG4=; b=qJPoO2d9w32upNZrOE2RiXOgBnPcCm7UNJaAi+9b8Go4sNy4kSwMVZso1Jtu+GHf7ZAxcY zSaVC2OUNIfeWomu5keX48ALGxrU26+XW06f56FmPUTxT76EJbKBDh+v4Cs6au7EgwrR+Q xQY/qGjH/vg5hSFajzNsc030NLvATsSgN7ywGT0J2PbH9OWjVkxFLYGaBFq/Gr3p5/6EDv VdSwdirqj4Qn5kfywWh1wFr5chv/iaKjSi1v9kGDyyHIOo9Q8iji0vuyBBv0uX6zK7AF87 l32Ct508DonjtTHN4HUhqckVw2uZF83qJkn2fXB6Ptf1XVsWFQ8iCxvIEXYlcg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1788197736; 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=n8Dx2ZMejgOo8yw+tVY8+elR2md2Nj5Pg4EyNxccHG4=; b=uAUN7GQ25ascWtQPuFVfw5GNklnNgydUcbK6hT5r30yvgbXUPW7ZdbCAa5+3V90E9Ckyc8 zILzpYba4I0NqEBA== From: "tip-bot2 for Jason Andryuk" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: x86/urgent] x86/amd_node: Avoid divide by zero on virtualized systems Cc: Borislav Petkov , Jason Andryuk , Yazen Ghannam , stable@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20260825214805.39148-2-jason.andryuk@amd.com> References: <20260825214805.39148-2-jason.andryuk@amd.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-ID: <178819773427.3717435.17649146675219220348.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: 72bd92bd8190d7869ecb462649ca40f297822a33 Gitweb: https://git.kernel.org/tip/72bd92bd8190d7869ecb462649ca40f29= 7822a33 Author: Jason Andryuk AuthorDate: Tue, 25 Aug 2026 17:48:02 -04:00 Committer: Borislav Petkov (AMD) CommitterDate: Sun, 30 Aug 2026 18:25:42 -07:00 x86/amd_node: Avoid divide by zero on virtualized systems On a virtualized system, the number of nodes does not have a relationship to the number of roots. A Xen PVH dom0 can calculate roots_per_node as 0, whi= ch crashes with a divide by zero in: if (count++ % roots_per_node) because the underlying topology code on Xen ends up making num_nodes 2 and num_roots 1 and the integer division result is 0. The issue is seen with Xen, but it could affect other systems. Set roots_per_node to 1 in this case. Print a firmware bug when this is performed for non-virtualized systems. [ bp: Massage commit message. ] Fixes: 0a4b61d9c2e4 ("x86/amd_node: Fix AMD root device caching") Suggested-by: Borislav Petkov Signed-off-by: Jason Andryuk Signed-off-by: Borislav Petkov (AMD) Reviewed-by: Yazen Ghannam Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260825214805.39148-2-jason.andryuk@amd.com --- arch/x86/kernel/amd_node.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/arch/x86/kernel/amd_node.c b/arch/x86/kernel/amd_node.c index 0be0172..408b9fd 100644 --- a/arch/x86/kernel/amd_node.c +++ b/arch/x86/kernel/amd_node.c @@ -287,6 +287,11 @@ static int __init amd_smn_init(void) return -ENOMEM; =20 roots_per_node =3D num_roots / num_nodes; + if (!roots_per_node) { + if (!cpu_feature_enabled(X86_FEATURE_HYPERVISOR)) + pr_warn(FW_BUG "Error detecting roots per node.\n"); + roots_per_node =3D 1; + } =20 count =3D 0; node =3D 0;