From nobody Sun Feb 8 11:06:48 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 80BF81E7C3F; Mon, 7 Apr 2025 14:44:34 +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=1744037078; cv=none; b=n4Bi8yrRd/3jjLnE9VCBpwF7yGblYfxkwznaDGEPhzAy8F/CKPf7cvArdSPwpt3EGleiFaxomvVg+2TOl9Wg3BH5LDmLBPEmLVgaTy0GgleRr8o+Aks1+1yV5Vyj1BNHDDydOiib3D/Fg+cHrdvLBnbBprmCs2omBZgLWm6wLJg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744037078; c=relaxed/simple; bh=wb5vmLAwjAr6Q5os1/SxsAfNsedbjZxVvWahckqyYwQ=; h=Date:From:To:Subject:Cc:In-Reply-To:References:MIME-Version: Message-ID:Content-Type; b=iTMEPFdA7sg9cU6NIxlB/x1C4ldPIJGE1lDsYZdv5g1emvsDdiR5Nv181f2869Hcvxghqlmmc60caThFFw54plwJY3vppgGzRONDO862F0SFswIwTmPyHH+SYaSPR74d9j/SlJcH2FPXc4hNXdJL1aXqVT8I88+um+m+Ghmue/U= 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=rCt58oB0; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=MNILQjjy; 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="rCt58oB0"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="MNILQjjy" Date: Mon, 07 Apr 2025 14:44:29 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1744037072; 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=j3s6DBTjHyxR82bXyvnXgDJ3sQDO7hl6/WU1SEmuqLQ=; b=rCt58oB0beAZUK1q8Ue6PuOcPPHE9qJ8tA08JSbrNfeRWlLESkKKCeBwa4Wx6lvMvQwasN Q+5enUW+n9BuzW2NOrKvRBh9CCpugkpXDm7a1ULFRv1+P4nyKGzdPEaTcuBQ6OqWWWgjr+ w64UWOhCBfjBAazDPNmU7WT7U7yhHrPlhDybXeyYnvo6EEKmFnO9CUAVFPzcZwKHkuGoWR UBceMBHsZ7/DNww6soTz8uniEG+ul80HVxVeN5JDPYZabbq8Sep2NFEglkfXIETDiZDySZ 5+OrNejDAvLJfe6badkqX6dPLo022ploTN7dMOniyAN6tFU8TNsX/BPgotjPnA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1744037072; 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=j3s6DBTjHyxR82bXyvnXgDJ3sQDO7hl6/WU1SEmuqLQ=; b=MNILQjjyGscMcijAd6AukIf1UcA7Br+pBQBrU9h46qPaDGNZqgUWFt9Uf8kxPeK5rdnnmZ cm8YiHCxClCi52Aw== From: tip-bot2 for Petr =?utf-8?q?Van=C4=9Bk?= Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: x86/urgent] x86/acpi: Don't limit CPUs to 1 for Xen PV guests due to disabled ACPI Cc: arkamar@atlas.cz, Thomas Gleixner , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20250407132445.6732-2-arkamar@atlas.cz> References: <20250407132445.6732-2-arkamar@atlas.cz> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-ID: <174403706955.31282.7031075757256146451.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: 8b37357a78d7fa13d88ea822b35b40137da1c85e Gitweb: https://git.kernel.org/tip/8b37357a78d7fa13d88ea822b35b40137= da1c85e Author: Petr Van=C4=9Bk AuthorDate: Mon, 07 Apr 2025 15:24:27 +02:00 Committer: Thomas Gleixner CommitterDate: Mon, 07 Apr 2025 16:35:21 +02:00 x86/acpi: Don't limit CPUs to 1 for Xen PV guests due to disabled ACPI Xen disables ACPI for PV guests in DomU, which causes acpi_mps_check() to return 1 when CONFIG_X86_MPPARSE is not set. As a result, the local APIC is disabled and the guest is later limited to a single vCPU, despite being configured with more. This regression was introduced in version 6.9 in commit 7c0edad3643f ("x86/cpu/topology: Rework possible CPU management"), which added an early check that limits CPUs to 1 if apic_is_disabled. Update the acpi_mps_check() logic to return 0 early when running as a Xen PV guest in DomU, preventing APIC from being disabled in this specific case and restoring correct multi-vCPU behaviour. Fixes: 7c0edad3643f ("x86/cpu/topology: Rework possible CPU management") Signed-off-by: Petr Van=C4=9Bk Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/all/20250407132445.6732-2-arkamar@atlas.cz --- arch/x86/kernel/acpi/boot.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c index dae6a73..9fa321a 100644 --- a/arch/x86/kernel/acpi/boot.c +++ b/arch/x86/kernel/acpi/boot.c @@ -23,6 +23,8 @@ #include #include =20 +#include + #include #include #include @@ -1729,6 +1731,15 @@ int __init acpi_mps_check(void) { #if defined(CONFIG_X86_LOCAL_APIC) && !defined(CONFIG_X86_MPPARSE) /* mptable code is not built-in*/ + + /* + * Xen disables ACPI in PV DomU guests but it still emulates APIC and + * supports SMP. Returning early here ensures that APIC is not disabled + * unnecessarily and the guest is not limited to a single vCPU. + */ + if (xen_pv_domain() && !xen_initial_domain()) + return 0; + if (acpi_disabled || acpi_noirq) { pr_warn("MPS support code is not built-in, using acpi=3Doff or acpi=3Dno= irq or pci=3Dnoacpi may have problem\n"); return 1;