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x86, irq: get nr_irqs from madt

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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>
This commit is contained in:
Yinghai Lu
2008-08-19 20:50:03 -07:00
committed by Ingo Molnar
parent a84488c213
commit 71f521bbaf
2 changed files with 29 additions and 2 deletions
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30
arch/x86/kernel/acpi/boot.c
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@ -957,6 +957,29 @@ void __init mp_register_ioapic(int id, u32 address, u32 gsi_base)
nr_ioapics++;
}
int get_nr_irqs_via_madt(void)
{
int idx;
int nr = 0;
for (idx = 0; idx < nr_ioapics; idx++) {
if (mp_ioapic_routing[idx].gsi_end > nr)
nr = mp_ioapic_routing[idx].gsi_end;
}
nr++;
/* double it for hotplug and msi and nmi */
nr <<= 1;
/* something wrong ? */
if (nr < 32)
nr = 32;
return nr;
}
static void assign_to_mp_irq(struct mp_config_intsrc *m,
struct mp_config_intsrc *mp_irq)
{
@ -1254,9 +1277,12 @@ static int __init acpi_parse_madt_ioapic_entries(void)
return count;
}
nr_irqs = get_nr_irqs_via_madt();
count =
acpi_table_parse_madt(ACPI_MADT_TYPE_INTERRUPT_OVERRIDE, acpi_parse_int_src_ovr,
NR_IRQ_VECTORS);
nr_irqs);
if (count < 0) {
printk(KERN_ERR PREFIX
"Error parsing interrupt source overrides entry\n");
@ -1276,7 +1302,7 @@ static int __init acpi_parse_madt_ioapic_entries(void)
count =
acpi_table_parse_madt(ACPI_MADT_TYPE_NMI_SOURCE, acpi_parse_nmi_src,
NR_IRQ_VECTORS);
nr_irqs);
if (count < 0) {
printk(KERN_ERR PREFIX "Error parsing NMI SRC entry\n");
/* TBD: Cleanup to allow fallback to MPS */