[PATCH] Multiple IO-APIC boot failure in all 2.4 kernels

[James Bottomley]

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This one's extremely wierd.  It may only affect Intel Alder derived 
motherboards (that's all I have with dual apics).  They refuse to boot all 2.4 
kernels SMP.

The problem is due to these errors:

PCI: Error while updating region 00:0f.0/1 (20000408 != 20000008)
PCI: Error while updating region 00:0f.0/2 (20000808 != 20000008)
PCI: Error while updating region 00:0f.0/3 (20000c08 != 20000008)
PCI: Error while updating region 00:0f.0/4 (20001008 != 20000008)
PCI: Error while updating region 00:0f.0/5 (20001408 != 20000008)

Beore the attempt to update this PCI resource, the secondary IO-APIC was 
mapped correctly.  However, after poking this region, the secondary IO-APIC 
disappears and consequently all interrupts routed through this io-apic are not 
delivered and the machine hangs.

The PCI details are:

00:0f.0 Class ff00: 8086:0008
        Subsystem: 1008:fec0
        Flags: fast devsel
        Memory at 20000000 (32-bit, prefetchable)
        Memory at 20000400 (32-bit, prefetchable)
        Memory at 20000800 (32-bit, prefetchable)
        Memory at 20000c00 (32-bit, prefetchable)
        Memory at 20001000 (32-bit, prefetchable)
        Memory at 20001400 (32-bit, prefetchable)

The attached patch works on the assumption that all things of class 0xff00 are 
some type of IO-APIC and prevents pcibios_update_resource() from poking it.  
However if anyone has a better suggestion, I'm open to trying it.

James Bottomley

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Index: arch/i386/kernel/pci-i386.c
===================================================================
RCS file: /home/jejb/CVSROOT/linux/2.4/arch/i386/kernel/pci-i386.c,v
retrieving revision 1.1.1.5
diff -u -r1.1.1.5 pci-i386.c
--- arch/i386/kernel/pci-i386.c	2001/07/06 14:42:02	1.1.1.5
+++ arch/i386/kernel/pci-i386.c	2001/10/31 01:15:44
@@ -112,6 +112,12 @@
 		/* Somebody might have asked allocation of a non-standard resource */
 		return;
 	}
+
+	if((dev->class >> 8) == 0xFF00) {
+		printk("PCI: device %s/%d belongs to IO-APIC, ignoring\n",
+		       dev->slot_name, resource);
+		return;
+	}
 	
 	pci_write_config_dword(dev, reg, new);
 	pci_read_config_dword(dev, reg, &check);

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