[PATCH] MAX_MP_BUSSES increase

From: James Cleverdon (jamesclv@us.ibm.com)
Date: Wed Dec 19 2001 - 23:28:22 EST

We've run into a bit of a problem with a forthcoming system. The BIOS
reserves so many PCI bus numbers for hotplug when maxed out PCI expansion
box(es) are present that some arrays (mp_bus_id_to_node[],
mp_bus_id_to_pci_bus[], etc) overflow, splattering important variables.

They've been predicting the time when 256 PCI busses are not enough for some
time now. We've nearly hit that point. Meanwhile, here's a patch to boost
MAX_MP_BUSSES from 32 to the max, plus one more for ISA.

Some folks might think that this is excessive, but the BIOS is adding 50 bus
records to the tables just for a quad computer and one fully loaded PCI
expansion box. (You can buy extra PCI slots in units of 6.) The thing is
supposed to support 3 expansion boxes soon. The NUMA version of this, coming
out next year, has the potential to be even more extreme: 4 quads with 3
expansion boxes each == a whole lot of PCI slots, each of which needs its own
PCI bus number in case someone hotplugs in a quad ethernet card or some other
combo board with its own PCI bridge chip.

Marcello and Linus, please apply.

--- linux-2.4.16/include/asm-i386/mpspec.h Thu Nov 22 11:46:18 2001
+++ jamesc-2.4.16/include/asm-i386/mpspec.h Tue Dec 18 13:45:49 2001
@@ -184,13 +185,10 @@
  * 7 2 CPU MCA+PCI
  */
 
-#ifdef CONFIG_MULTIQUAD
-#define MAX_IRQ_SOURCES 512
-#else /* !CONFIG_MULTIQUAD */
-#define MAX_IRQ_SOURCES 256
-#endif /* CONFIG_MULTIQUAD */
+#define MAX_MP_BUSSES 257 /* Need max PCI busses for hotplug + 1 for ISA. */
+ /* Four intrs per PCI slot. */
+#define MAX_IRQ_SOURCES (MAX_MP_BUSSES * 4)
 
-#define MAX_MP_BUSSES 32
 enum mp_bustype {
         MP_BUS_ISA = 1,
         MP_BUS_EISA, 

-- 
James Cleverdon, IBM xSeries Platform (NUMA), Beaverton
jamesclv@us.ibm.com (kmail)  |   cleverdj@us.ibm.com (Lotus Notes)

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This archive was generated by hypermail 2b29 : Sun Dec 23 2001 - 21:00:20 EST