[Xen-devel] [PATCH 05/23] xen: identity map gsi->irqs

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

From: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>

Impact: preserve compat with native

Reserve the lower irq range for use for hardware interrupts so we
can identity-map them.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
 drivers/xen/events.c |   23 +++++++++++++++++------
 1 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index b8f030a..8eeb808 100644
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -33,6 +33,7 @@
 #include <asm/ptrace.h>
 #include <asm/irq.h>
 #include <asm/idle.h>
+#include <asm/io_apic.h>
 #include <asm/sync_bitops.h>
 #include <asm/xen/hypercall.h>
 #include <asm/xen/hypervisor.h>
@@ -46,9 +47,6 @@
 #include <xen/interface/hvm/hvm_op.h>
 #include <xen/interface/hvm/params.h>
 
-/* Leave low irqs free for identity mapping */
-#define LEGACY_IRQS    16
-
 /*
  * This lock protects updates to the following mapping and reference-count
  * arrays. The lock does not need to be acquired to read the mapping tables.
@@ -351,12 +349,24 @@ static void unmask_evtchn(int port)
        put_cpu();
 }
 
+static int get_nr_hw_irqs(void)
+{
+       int ret = 1;
+
+#ifdef CONFIG_X86_IO_APIC
+       ret = get_nr_irqs_gsi();
+#endif
+
+       return ret;
+}
+
 static int find_unbound_irq(void)
 {
        int irq;
        struct irq_desc *desc;
+       int start = get_nr_hw_irqs();
 
-       for (irq = 0; irq < nr_irqs; irq++) {
+       for (irq = start; irq < nr_irqs; irq++) {
                desc = irq_to_desc(irq);
                /* only 0->15 have init'd desc; handle irq > 16 */
                if (desc == NULL)
@@ -383,8 +393,8 @@ static int find_unbound_irq(void)
 
 static bool identity_mapped_irq(unsigned irq)
 {
-       /* only identity map legacy irqs */
-       return irq < LEGACY_IRQS;
+       /* identity map all the hardware irqs */
+       return irq < get_nr_hw_irqs();
 }
 
 static void pirq_unmask_notify(int irq)
@@ -553,6 +563,7 @@ int xen_allocate_pirq(unsigned gsi)
 
        if (identity_mapped_irq(gsi)) {
                irq = gsi;
+               irq_to_desc_alloc_node(irq, 0);
                dynamic_irq_init(irq);
        } else
                irq = find_unbound_irq();
-- 
1.7.0.4


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