[Xen-devel] [PATCH v3] x86: Fixup IRQs when CPUs go down during shutdown

[Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>]

Commit fc0c3fa2ad5c ("x86/IO-APIC: fix setup of Xen internally used IRQs
(take 2)") introduced a regression on some hardware where Xen would hang
during shutdown, repeating the following message:
APIC error on CPU0: 08(08), Receive accept error

This appears to be because an interrupt (in this case from the serial
console) destined for a CPU other than the boot CPU is left unhandled so
an APIC error on CPU 0 is generated instead.

To fix this, before taking down the non-boot CPUs, call fixup_irqs()
with a CPU mask of only the boot CPU to reset the IRQ affinities
correctly.

Signed-off-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
---
v3:
* Don't call fixup_eoi() in shutdown path
* Use cpumask_of
* Update comments
* Reduce code churn

 xen/arch/x86/irq.c        | 28 ++++++++++++++++++----------
 xen/arch/x86/smp.c        |  4 ++++
 xen/arch/x86/smpboot.c    |  3 ++-
 xen/include/asm-x86/irq.h |  5 +++--
 4 files changed, 27 insertions(+), 13 deletions(-)

diff --git a/xen/arch/x86/irq.c b/xen/arch/x86/irq.c
index 5f515a0..1228568 100644
--- a/xen/arch/x86/irq.c
+++ b/xen/arch/x86/irq.c
@@ -2328,14 +2328,12 @@ static int __init setup_dump_irqs(void)
 }
 __initcall(setup_dump_irqs);
 
-/* A cpu has been removed from cpu_online_mask.  Re-set irq affinities. */
-void fixup_irqs(void)
+/* Reset irq affinities to match the given CPU mask. */
+void fixup_irqs(const cpumask_t *mask, bool_t verbose)
 {
-    unsigned int irq, sp;
+    unsigned int irq;
     static int warned;
     struct irq_desc *desc;
-    irq_guest_action_t *action;
-    struct pending_eoi *peoi;
 
     for ( irq = 0; irq < nr_irqs; irq++ )
     {
@@ -2355,21 +2353,20 @@ void fixup_irqs(void)
         vector = irq_to_vector(irq);
         if ( vector >= FIRST_HIPRIORITY_VECTOR &&
              vector <= LAST_HIPRIORITY_VECTOR )
-            cpumask_and(desc->arch.cpu_mask, desc->arch.cpu_mask,
-                        &cpu_online_map);
+            cpumask_and(desc->arch.cpu_mask, desc->arch.cpu_mask, mask);
 
         cpumask_copy(&affinity, desc->affinity);
-        if ( !desc->action || cpumask_subset(&affinity, &cpu_online_map) )
+        if ( !desc->action || cpumask_subset(&affinity, mask) )
         {
             spin_unlock(&desc->lock);
             continue;
         }
 
-        cpumask_and(&affinity, &affinity, &cpu_online_map);
+        cpumask_and(&affinity, &affinity, mask);
         if ( cpumask_empty(&affinity) )
         {
             break_affinity = 1;
-            cpumask_copy(&affinity, &cpu_online_map);
+            cpumask_copy(&affinity, mask);
         }
 
         if ( desc->handler->disable )
@@ -2385,6 +2382,9 @@ void fixup_irqs(void)
 
         spin_unlock(&desc->lock);
 
+        if ( !verbose )
+            continue;
+
         if ( break_affinity && set_affinity )
             printk("Broke affinity for irq %i\n", irq);
         else if ( !set_affinity )
@@ -2395,6 +2395,14 @@ void fixup_irqs(void)
     local_irq_enable();
     mdelay(1);
     local_irq_disable();
+}
+
+void fixup_eoi(void)
+{
+    unsigned int irq, sp;
+    struct irq_desc *desc;
+    irq_guest_action_t *action;
+    struct pending_eoi *peoi;
 
     /* Clean up cpu_eoi_map of every interrupt to exclude this CPU. */
     for ( irq = 0; irq < nr_irqs; irq++ )
diff --git a/xen/arch/x86/smp.c b/xen/arch/x86/smp.c
index 50ff6c2..988b9c2 100644
--- a/xen/arch/x86/smp.c
+++ b/xen/arch/x86/smp.c
@@ -299,6 +299,10 @@ void smp_send_stop(void)
 {
     int timeout = 10;
 
+    local_irq_disable();
+    fixup_irqs(cpumask_of(smp_processor_id()), 0);
+    local_irq_enable();
+
     smp_call_function(stop_this_cpu, NULL, 0);
 
     /* Wait 10ms for all other CPUs to go offline. */
diff --git a/xen/arch/x86/smpboot.c b/xen/arch/x86/smpboot.c
index 5d48bac..1eb16cb 100644
--- a/xen/arch/x86/smpboot.c
+++ b/xen/arch/x86/smpboot.c
@@ -922,7 +922,8 @@ void __cpu_disable(void)
 
     /* It's now safe to remove this processor from the online map */
     cpumask_clear_cpu(cpu, &cpu_online_map);
-    fixup_irqs();
+    fixup_irqs(&cpu_online_map, 1);
+    fixup_eoi();
 
     if ( cpu_disable_scheduler(cpu) )
         BUG();
diff --git a/xen/include/asm-x86/irq.h b/xen/include/asm-x86/irq.h
index fcf37a3..7efdd37 100644
--- a/xen/include/asm-x86/irq.h
+++ b/xen/include/asm-x86/irq.h
@@ -148,8 +148,9 @@ int map_domain_emuirq_pirq(struct domain *d, int pirq, int 
irq);
 int unmap_domain_pirq_emuirq(struct domain *d, int pirq);
 bool_t hvm_domain_use_pirq(const struct domain *, const struct pirq *);
 
-/* A cpu has been removed from cpu_online_mask.  Re-set irq affinities. */
-void fixup_irqs(void);
+/* Reset irq affinities to match the given CPU mask. */
+void fixup_irqs(const cpumask_t *mask, bool_t verbose);
+void fixup_eoi(void);
 
 int  init_irq_data(void);
 
-- 
2.4.3


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