x86, irq: get nr_irqs from madt
Until now, NR_IRQS was derived from black magic defines that had to
be "large enough" to both accomodate NR_CPUS and MAX_NR_IO_APICs.
This resulted in a way too large irq_desc[] array on most x86 systems.
Especially with larger CPU masks, the size of irq_desc can spiral out
of control quickly.
So be smarter about it and use precise allocation instead: determine the
default maximum possible IRQ number from the ACPI MADT. Use a minimum limit
of at least 32 IRQs for broken BIOSes.
Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/include/asm-x86/mpspec.h b/include/asm-x86/mpspec.h
index be2241a..a074802 100644
--- a/include/asm-x86/mpspec.h
+++ b/include/asm-x86/mpspec.h
@@ -60,6 +60,7 @@
u32 gsi);
extern void mp_config_acpi_legacy_irqs(void);
extern int mp_register_gsi(u32 gsi, int edge_level, int active_high_low);
+extern int get_nr_irqs_via_madt(void);
#ifdef CONFIG_X86_IO_APIC
extern int mp_config_acpi_gsi(unsigned char number, unsigned int devfn, u8 pin,
u32 gsi, int triggering, int polarity);