[PATCH] i386/x86-64: Share interrupt vectors when there is a large number of interrupt sources

Here's a patch that builds on Natalie Protasevich's IRQ compression
patch and tries to work for MPS boots as well as ACPI.  It is meant for
a 4-node IBM x460 NUMA box, which was dying because it had interrupt
pins with GSI numbers > NR_IRQS and thus overflowed irq_desc.

The problem is that this system has 270 GSIs (which are 1:1 mapped with
I/O APIC RTEs) and an 8-node box would have 540.  This is much bigger
than NR_IRQS (224 for both i386 and x86_64).  Also, there aren't enough
vectors to go around.  There are about 190 usable vectors, not counting
the reserved ones and the unused vectors at 0x20 to 0x2F.  So, my patch
attempts to compress the GSI range and share vectors by sharing IRQs.

Cc: "Protasevich, Natalie" <Natalie.Protasevich@unisys.com>

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 7 insertions, 8 deletions

diff --git a/arch/i386/kernel/acpi/boot.c b/arch/i386/kernel/acpi/boot.c
index b66c13c0cc0f..82754bb80e20 100644
--- a/arch/i386/kernel/acpi/boot.c
+++ b/arch/i386/kernel/acpi/boot.c
@@ -39,17 +39,14 @@
 
 #ifdef  CONFIG_X86_64
 
-static inline void acpi_madt_oem_check(char *oem_id, char *oem_table_id)
-{
-}
 extern void __init clustered_apic_check(void);
-static inline int ioapic_setup_disabled(void)
-{
-        return 0;
-}
 
+extern int gsi_irq_sharing(int gsi);
 #include <asm/proto.h>
 
+static inline int acpi_madt_oem_check(char *oem_id, char *oem_table_id) { return 0; }
+
+
 #else                           /* X86 */
 
 #ifdef  CONFIG_X86_LOCAL_APIC
@@ -57,6 +54,8 @@ static inline int ioapic_setup_disabled(void)
 #include <mach_mpparse.h>
 #endif                          /* CONFIG_X86_LOCAL_APIC */
 
+static inline int gsi_irq_sharing(int gsi) { return gsi; }
+
 #endif                          /* X86 */
 
 #define BAD_MADT_ENTRY(entry, end) (                                        \
@@ -459,7 +458,7 @@ int acpi_gsi_to_irq(u32 gsi, unsigned int *irq)
                 *irq = IO_APIC_VECTOR(gsi);
         else
 #endif
-                *irq = gsi;
+                *irq = gsi_irq_sharing(gsi);
         return 0;
 }