[Xen-devel] [PATCH v2] [Bugfix] x86/apic: Fix xen IRQ allocation failure caused by commit b81975eade8c

[Jiang Liu <jiang.liu@xxxxxxxxxxxxxxx>]

Commit b81975eade8c ("x86, irq: Clean up irqdomain transition code")
breaks xen IRQ allocation because xen_smp_prepare_cpus() doesn't invoke
setup_IO_APIC(), so no irqdomains created for IOAPICs and
mp_map_pin_to_irq() fails at the very beginning.

Enhance xen_smp_prepare_cpus() to call setup_IO_APIC() to initialize
irqdomain for IOAPICs.

Signed-off-by: Jiang Liu <jiang.liu@xxxxxxxxxxxxxxx>
---
Hi Sander,
        Could you please help to test this patch against 3.19-rc3?
I have reworked it based Konrad's suggestions.
Thanks!
Gerry
---
 arch/x86/kernel/apic/io_apic.c |   31 +++++++++++++++++++++++--------
 arch/x86/xen/smp.c             |    1 +
 2 files changed, 24 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index 3f5f60406ab1..81d4faeb8040 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -38,6 +38,8 @@
 #include <linux/slab.h>
 #include <linux/bootmem.h>
 
+#include <xen/xen.h>
+
 #include <asm/idle.h>
 #include <asm/io.h>
 #include <asm/smp.h>
@@ -2165,6 +2167,9 @@ static inline void __init check_timer(void)
        unsigned long flags;
        int no_pin1 = 0;
 
+       if (!nr_legacy_irqs())
+               return;
+
        local_irq_save(flags);
 
        /*
@@ -2185,6 +2190,13 @@ static inline void __init check_timer(void)
        apic_write(APIC_LVT0, APIC_LVT_MASKED | APIC_DM_EXTINT);
        legacy_pic->init(1);
 
+       /*
+        * legacy_pic will be changed to null_legacy_pic if init() fails to
+        * to detect legacy PIC hardware. Recheck again.
+        */
+       if (!nr_legacy_irqs())
+               goto out;
+
        pin1  = find_isa_irq_pin(0, mp_INT);
        apic1 = find_isa_irq_apic(0, mp_INT);
        pin2  = ioapic_i8259.pin;
@@ -2369,6 +2381,15 @@ static void ioapic_destroy_irqdomain(int idx)
        ioapics[idx].pin_info = NULL;
 }
 
+static void setup_IO_APIC_IDs(void)
+{
+       if (xen_domain())
+               return;
+
+       x86_init.mpparse.setup_ioapic_ids();
+       sync_Arb_IDs();
+}
+
 void __init setup_IO_APIC(void)
 {
        int ioapic;
@@ -2382,16 +2403,10 @@ void __init setup_IO_APIC(void)
        for_each_ioapic(ioapic)
                BUG_ON(mp_irqdomain_create(ioapic));
 
-       /*
-         * Set up IO-APIC IRQ routing.
-         */
-       x86_init.mpparse.setup_ioapic_ids();
-
-       sync_Arb_IDs();
+       setup_IO_APIC_IDs();
        setup_IO_APIC_irqs();
        init_IO_APIC_traps();
-       if (nr_legacy_irqs())
-               check_timer();
+       check_timer();
 
        ioapic_initialized = 1;
 }
diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
index 4c071aeb8417..9f404df64422 100644
--- a/arch/x86/xen/smp.c
+++ b/arch/x86/xen/smp.c
@@ -327,6 +327,7 @@ static void __init xen_smp_prepare_cpus(unsigned int 
max_cpus)
                xen_raw_printk(m);
                panic(m);
        }
+       setup_IO_APIC();
        xen_init_lock_cpu(0);
 
        smp_store_boot_cpu_info();
-- 
1.7.10.4


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