Re: [RFC][2.6.12.3] IRQ compression/sharing patch

James Cleverdon
2005-08-12T03:00:00Z

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The attached hack to assign_irq_vector may be marginally less ugly.
However, I haven't rearranged the code like Andi wanted yet.

On Thursday 11 August 2005 02:55 pm, Protasevich, Natalie wrote:
> > After sleeping on it, maybe the original code can be patched
> > without having to hack assign_irq_vector(), etc. How about:
> >
> > --- io_apic.c 2005-08-11 10:14:33.564748923 -0700
> > +++ io_apic.c.new 2005-08-11 10:15:55.412331115 -0700
> > @@ -617,7 +617,7 @@ int gsi_irq_sharing(int gsi)
> > * than PCI.
> > */
> > for (i = 0; i < NR_IRQS; i++)
> > - if (IO_APIC_VECTOR(i) == vector) {
> > + if (IO_APIC_VECTOR(i) == vector && i != gsi) {
> > if (!platform_legacy_irq(i))
> > break; /* got one */
> > IO_APIC_VECTOR(gsi) = 0;
> >
> >
> Yes that did it, on my small system it looked just right:
>
> <7>IRQ to pin mappings:
> <7>IRQ0 -> 0:2
> <7>IRQ1 -> 0:1
> <7>IRQ3 -> 0:3
> <7>IRQ4 -> 0:4
> <7>IRQ5 -> 0:5
> <7>IRQ6 -> 0:6
> <7>IRQ7 -> 0:7
> <7>IRQ8 -> 0:8
> <7>IRQ9 -> 0:9
> <7>IRQ10 -> 0:10
> <7>IRQ11 -> 0:11
> <7>IRQ12 -> 0:12
> <7>IRQ14 -> 0:14
> <7>IRQ15 -> 0:15
> <7>IRQ16 -> 0:16
> <7>IRQ17 -> 0:17
> <7>IRQ18 -> 0:18
> <7>IRQ19 -> 0:19
> <7>IRQ20 -> 0:20
> <7>IRQ21 -> 0:23
> <7>IRQ22 -> 1:2
> <7>IRQ23 -> 1:3
> <7>IRQ24 -> 1:4
> <7>IRQ25 -> 1:5
> <7>IRQ26 -> 2:0
> <7>IRQ27 -> 2:1
> <7>IRQ28 -> 2:2
> <7>IRQ29 -> 2:3
> <7>IRQ30 -> 2:4
> <7>IRQ31 -> 2:5
> <7>IRQ32 -> 2:6
> <7>IRQ33 -> 2:7
> <7>IRQ34 -> 2:8
> :!cat /proc/interrupts
> CPU0 CPU1 CPU2 CPU3
> 0: 12621 15007 12781 20921 IO-APIC-edge timer
> 1: 72 0 2 175 IO-APIC-edge i8042
> 2: 0 0 0 0 XT-PIC
> cascade
> 8: 0 0 0 1 IO-APIC-edge rtc
> 9: 0 0 0 0 IO-APIC-edge acpi
> 12: 4 272 0 110 IO-APIC-edge i8042
> 15: 4 0 0 39 IO-APIC-edge ide1
> 16: 0 0 0 0 IO-APIC-level
> uhci_hcd:usb1, uhci_hcd:usb4
> 17: 0 0 0 2 IO-APIC-level
> ohci1394
> 18: 730 2407 932 2083 IO-APIC-level
> libata, uhci_hcd:usb3
> 19: 0 0 0 0 IO-APIC-level
> uhci_hcd:usb2
> 21: 0 0 0 0 IO-APIC-level
> ehci_hcd:usb5
> 26: 416 0 0 4 IO-APIC-level eth0
> NMI: 116 71 73 51
> LOC: 61280 61258 61236 61214
> ERR: 3
> MIS: 0
>
> Looks good! I will try the patch also on the ES7000 hopefully big enough
> to exercise some vector sharing.
>
> Regards,
> --Natalie
>
>
>

--
James Cleverdon
IBM LTC (xSeries Linux Solutions)
{jamesclv(Unix, preferred), cleverdj(Notes)} at us dot ibm dot comm

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diff -pru 2.6.12.3/arch/i386/kernel/acpi/boot.c z12.3/arch/i386/kernel/acpi/boot.c
--- 2.6.12.3/arch/i386/kernel/acpi/boot.c 2005-07-15 14:18:57.000000000 -0700
+++ z12.3/arch/i386/kernel/acpi/boot.c 2005-08-11 19:27:46.000000000 -0700
@@ -42,6 +42,7 @@
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>

#else /* X86 */
@@ -51,6 +52,9 @@ static inline int ioapic_setup_disabled(
#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) ( \
@@ -453,7 +457,7 @@ int acpi_gsi_to_irq(u32 gsi, unsigned in
*irq = IO_APIC_VECTOR(gsi);
else
#endif
- *irq = gsi;
+ *irq = gsi_irq_sharing(gsi);
return 0;
}

diff -pru 2.6.12.3/arch/x86_64/kernel/io_apic.c z12.3/arch/x86_64/kernel/io_apic.c
--- 2.6.12.3/arch/x86_64/kernel/io_apic.c 2005-07-15 14:18:57.000000000 -0700
+++ z12.3/arch/x86_64/kernel/io_apic.c 2005-08-11 19:32:28.000000000 -0700
@@ -56,7 +56,7 @@ int nr_ioapic_registers[MAX_IO_APICS];
* Rough estimation of how many shared IRQs there are, can
* be changed anytime.
*/
-#define MAX_PLUS_SHARED_IRQS NR_IRQS
+#define MAX_PLUS_SHARED_IRQS NR_IRQ_VECTORS
#define PIN_MAP_SIZE (MAX_PLUS_SHARED_IRQS + NR_IRQS)

/*
@@ -88,6 +88,7 @@ static void add_pin_to_irq(unsigned int
static int first_free_entry = NR_IRQS;
struct irq_pin_list *entry = irq_2_pin + irq;

+ BUG_ON(irq >= NR_IRQS);
while (entry->next)
entry = irq_2_pin + entry->next;

@@ -95,7 +96,7 @@ static void add_pin_to_irq(unsigned int
entry->next = first_free_entry;
entry = irq_2_pin + entry->next;
if (++first_free_entry >= PIN_MAP_SIZE)
- panic("io_apic.c: whoops");
+ panic("io_apic.c: ran out of irq_2_pin entries!");
}
entry->apic = apic;
entry->pin = pin;
@@ -581,6 +582,69 @@ static inline int irq_trigger(int idx)
return MPBIOS_trigger(idx);
}

+static int __assign_irq_vector(int irq);
+
+static int next_irq = 16;
+
+static u8 gsi_2_irq[NR_IRQ_VECTORS] = { [0 ... NR_IRQ_VECTORS-1] = 0xFF };
+
+/*
+ * gsi_irq_sharing -- Name overload! "irq" can be either a legacy IRQ
+ * in the range 0-15, a linux IRQ in the range 0-223, or a GSI number
+ * from ACPI, which can reach 800 in large boxen.
+ *
+ * Compact the sparse GSI space into a sequential IRQ series and reuse
+ * vectors if possible.
+ */
+int gsi_irq_sharing(int gsi)
+{
+ int i, tries, vector;
+
+ BUG_ON(gsi >= NR_IRQ_VECTORS);
+
+ if (platform_legacy_irq(gsi)) {
+ gsi_2_irq[gsi] = gsi;
+ return gsi;
+ }
+
+ if (gsi_2_irq[gsi] != 0xFF)
+ return (int)gsi_2_irq[gsi];
+
+ tries = NR_IRQS;
+ try_again:
+ vector = __assign_irq_vector(gsi);
+
+ /*
+ * Sharing vectors means sharing IRQs, so scan irq_vectors for previous
+ * use of vector and if found, return that IRQ. However, we never want
+ * to share legacy IRQs, which usually have a different trigger mode
+ * than PCI.
+ */
+ for (i = 0; i < NR_IRQS; i++)
+ if (IO_APIC_VECTOR(i) == vector)
+ break;
+ if (platform_legacy_irq(i)) {
+ if (--tries >= 0)
+ goto try_again;
+ panic("gsi_irq_sharing: didn't find an IRQ using vector 0x%02X for GSI %d", vector, gsi);
+ }
+ if (i < NR_IRQS) {
+ gsi_2_irq[gsi] = i;
+ printk(KERN_INFO "GSI %d sharing vector 0x%02X and IRQ %d\n",
+ gsi, vector, i);
+ return i;
+ }
+
+ i = next_irq++;
+ BUG_ON(i >= NR_IRQS);
+ gsi_2_irq[gsi] = i;
+ IO_APIC_VECTOR(i) = vector;
+ vector_irq[vector] = i;
+ printk(KERN_INFO "GSI %d assigned vector 0x%02X and IRQ %d\n",
+ gsi, vector, i);
+ return i;
+}
+
static int pin_2_irq(int idx, int apic, int pin)
{
int irq, i;
@@ -610,6 +674,7 @@ static int pin_2_irq(int idx, int apic,
while (i < apic)
irq += nr_ioapic_registers[i++];
irq += pin;
+ irq = gsi_irq_sharing(irq);
break;
}
default:
@@ -619,6 +684,7 @@ static int pin_2_irq(int idx, int apic,
break;
}
}
+ BUG_ON(irq >= NR_IRQS);

/*
* PCI IRQ command line redirection. Yes, limits are hardcoded.
@@ -634,6 +700,7 @@ static int pin_2_irq(int idx, int apic,
}
}
}
+ BUG_ON(irq >= NR_IRQS);
return irq;
}

@@ -657,12 +724,12 @@ static inline int IO_APIC_irq_trigger(in
/* irq_vectors is indexed by the sum of all RTEs in all I/O APICs. */
u8 irq_vector[NR_IRQ_VECTORS] = { FIRST_DEVICE_VECTOR , 0 };

-int assign_irq_vector(int irq)
+static int __assign_irq_vector(int irq)
{
static int current_vector = FIRST_DEVICE_VECTOR, offset = 0;

- BUG_ON(irq >= NR_IRQ_VECTORS);
- if (IO_APIC_VECTOR(irq) > 0)
+ BUG_ON(irq != AUTO_ASSIGN && (unsigned)irq >= NR_IRQ_VECTORS);
+ if (irq != AUTO_ASSIGN && IO_APIC_VECTOR(irq) > 0)
return IO_APIC_VECTOR(irq);
next:
current_vector += 8;
@@ -670,17 +737,24 @@ next:
goto next;

if (current_vector >= FIRST_SYSTEM_VECTOR) {
- offset++;
- if (!(offset%8))
- return -ENOSPC;
+ /* If we run out of vectors on large boxen, must share them. */
+ offset = (offset + 1) % 8;
current_vector = FIRST_DEVICE_VECTOR + offset;
}

- vector_irq[current_vector] = irq;
+ return current_vector;
+}
+
+int assign_irq_vector(int irq)
+{
+ int vect;
+
+ vect = __assign_irq_vector(irq);
+ vector_irq[vect] = irq;
if (irq != AUTO_ASSIGN)
- IO_APIC_VECTOR(irq) = current_vector;
+ IO_APIC_VECTOR(irq) = vect;

- return current_vector;
+ return vect;
}

extern void (*interrupt[NR_IRQS])(void);
@@ -1866,6 +1940,7 @@ int io_apic_set_pci_routing (int ioapic,
entry.polarity = active_high_low;
entry.mask = 1; /* Disabled (masked) */

+ irq = gsi_irq_sharing(irq);
/*
* IRQs < 16 are already in the irq_2_pin[] map
*/
diff -pru 2.6.12.3/arch/x86_64/kernel/mpparse.c z12.3/arch/x86_64/kernel/mpparse.c
--- 2.6.12.3/arch/x86_64/kernel/mpparse.c 2005-07-15 14:18:57.000000000 -0700
+++ z12.3/arch/x86_64/kernel/mpparse.c 2005-08-11 19:34:53.000000000 -0700
@@ -214,7 +214,7 @@ static void __init MP_intsrc_info (struc
m->mpc_irqtype, m->mpc_irqflag & 3,
(m->mpc_irqflag >> 2) & 3, m->mpc_srcbus,
m->mpc_srcbusirq, m->mpc_dstapic, m->mpc_dstirq);
- if (++mp_irq_entries == MAX_IRQ_SOURCES)
+ if (++mp_irq_entries >= MAX_IRQ_SOURCES)
panic("Max # of irq sources exceeded!!\n");
}

diff -pru 2.6.12.3/include/asm-x86_64/mpspec.h z12.3/include/asm-x86_64/mpspec.h
--- 2.6.12.3/include/asm-x86_64/mpspec.h 2005-07-15 14:18:57.000000000 -0700
+++ z12.3/include/asm-x86_64/mpspec.h 2005-08-10 17:08:45.000000000 -0700
@@ -157,7 +157,8 @@ struct mpc_config_lintsrc
*/

#define MAX_MP_BUSSES 256
-#define MAX_IRQ_SOURCES 256
+/* Each PCI slot may be a combo card with its own bus. 4 IRQ pins per slot. */
+#define MAX_IRQ_SOURCES (MAX_MP_BUSSES * 4)
enum mp_bustype {
MP_BUS_ISA = 1,
MP_BUS_EISA,