xen/x86: actually allocate legacy interrupts on PV guests

b4ff8389ed14 is incomplete: relies on nr_legacy_irqs() to get the number
of legacy interrupts when actually nr_legacy_irqs() returns 0 after
probe_8259A(). Use NR_IRQS_LEGACY instead.

Signed-off-by: Stefano Stabellini <sstabellini@kernel.org>
CC: stable@vger.kernel.org

1 files changed, 5 insertions, 2 deletions

diff --git a/arch/x86/pci/xen.c b/arch/x86/pci/xen.c
index beac4dfdade6..349b8ce92bf2 100644
--- a/arch/x86/pci/xen.c
+++ b/arch/x86/pci/xen.c
@@ -491,8 +491,11 @@ int __init pci_xen_initial_domain(void)
 #endif
         __acpi_register_gsi = acpi_register_gsi_xen;
         __acpi_unregister_gsi = NULL;
-        /* Pre-allocate legacy irqs */
-        for (irq = 0; irq < nr_legacy_irqs(); irq++) {
+        /*
+         * Pre-allocate the legacy IRQs.  Use NR_LEGACY_IRQS here
+         * because we don't have a PIC and thus nr_legacy_irqs() is zero.
+         */
+        for (irq = 0; irq < NR_IRQS_LEGACY; irq++) {
                 int trigger, polarity;
 
                 if (acpi_get_override_irq(irq, &trigger, &polarity) == -1)