linux-kernel - Re: PCI MSI breaks when booting with nosmp

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Message-Id: <200804211414.45629.jbarnes@virtuousgeek.org>
Date:	Mon, 21 Apr 2008 14:14:44 -0700
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Jean Delvare <jdelvare@...e.de>,
	linux-pci@...ey.karlin.mff.cuni.cz,
	LKML <linux-kernel@...r.kernel.org>, Pavel Machek <pavel@....cz>,
	Tejun Heo <htejun@...il.com>,
	Tom Long Nguyen <tom.l.nguyen@...el.com>,
	Randy Dunlap <rdunlap@...otime.net>,
	Jeff Garzik <jgarzik@...ox.com>
Subject: Re: PCI MSI breaks when booting with nosmp

On Monday, April 21, 2008 2:09 pm Andi Kleen wrote:
> > Both call disable_ioapic_setup(), so how can they not be the same?
>
> See Jesse's explanation. Basically there is special code in the smp
> boot up to handle 0 CPUs and it disables all APICs.
>
> This is very old and crufty and somewhat obsolete logic,
> but it is like that.

This might be closer to a real fix.  Can you confirm that this works for you 
Jean?

Thanks,
Jesse

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index e6abe8a..7cdf930 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -1138,14 +1138,10 @@ static int __init smp_sanity_check(unsigned max_cpus)
 				 "forcing use of dummy APIC emulation.\n");
 		smpboot_clear_io_apic();
 #ifdef CONFIG_X86_32
-		if (nmi_watchdog == NMI_LOCAL_APIC) {
-			printk(KERN_INFO "activating minimal APIC for"
-					 "NMI watchdog use.\n");
-			connect_bsp_APIC();
-			setup_local_APIC();
-			end_local_APIC_setup();
-		}
+		connect_bsp_APIC();
 #endif
+		setup_local_APIC();
+		end_local_APIC_setup();
 		return -1;
 	}
 

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