From mboxrd@z Thu Jan 1 00:00:00 1970 From: Len Brown Subject: Re: SMP broken on pre-ACPI machine. Date: Thu, 19 Oct 2006 01:33:40 -0400 Message-ID: <200610190133.40581.len.brown@intel.com> References: <20061018222433.GA4770@redhat.com> Reply-To: Len Brown Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Return-path: Received: from hera.kernel.org ([140.211.167.34]:28577 "EHLO hera.kernel.org") by vger.kernel.org with ESMTP id S1161019AbWJSFbS (ORCPT ); Thu, 19 Oct 2006 01:31:18 -0400 In-Reply-To: <20061018222433.GA4770@redhat.com> Content-Disposition: inline Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: Dave Jones Cc: Linux Kernel , linux-acpi@vger.kernel.org On Wednesday 18 October 2006 18:24, Dave Jones wrote: > I've been chasing a bug that got filed against the Fedora kernel > a while back: https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=199052 > This is a dual pentium pro from an era before we had ACPI, and > it seems to be falling foul of this test in smpboot.c .. > > if (!smp_found_config && !acpi_lapic) { > printk(KERN_NOTICE "SMP motherboard not detected.\n"); > smpboot_clear_io_apic_irqs(); > phys_cpu_present_map = physid_mask_of_physid(0); > if (APIC_init_uniprocessor()) > printk(KERN_NOTICE "Local APIC not detected." > " Using dummy APIC emulation.\n"); > map_cpu_to_logical_apicid(); > cpu_set(0, cpu_sibling_map[0]); > cpu_set(0, cpu_core_map[0]); > return; > } > > > My initial reaction is that the !acpi_lapic test should be conditional > on some variable that gets set if the ACPI parsing actually succeeded. acpi_lapic isn't related to the problem at hand -- that smp_found_config is not set. That said, allowing acpi_lapic=1 to bail out of this check has the sole function of allowing SMP/PIC configurations. (smp_found_config in ACPI mode is set if acpi_lapic and acpi_ioapic are set) SMP/PIC configurations are not very interesting, except for debugging. Indeed, MPS prohibits them by mandating an IOAPIC be present for SMP -- but ACPI has no such rule. -Len