[patch 50/52] x86/vector: Switch IOAPIC to global reservation mode

Thomas Gleixner
2017-09-13T21:36:06Z

[-- Attachment #1: x86-vector--Switch-IOAPIC-to-global-reservation-mode.patch --]
[-- Type: text/plain, Size: 3251 bytes --]

IOAPICs install and allocate vectors for inactive interrupts. This results
in problems on CPU offline and wastes vector resources for nothing.

Handle inactive IOAPIC interrupts in the same way as inactive MSI
interrupts and switch them to the global reservation mode.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
arch/x86/kernel/apic/vector.c | 56 ++++++++++++++++++++++++------------------
1 file changed, 33 insertions(+), 23 deletions(-)

Index: b/arch/x86/kernel/apic/vector.c
===================================================================
--- a/arch/x86/kernel/apic/vector.c
+++ b/arch/x86/kernel/apic/vector.c
@@ -258,17 +258,6 @@ static int assign_irq_vector_any_locked(
return assign_vector_locked(irqd, cpu_online_mask);
}

-static int assign_irq_vector_any(struct irq_data *irqd)
-{
- unsigned long flags;
- int ret;
-
- raw_spin_lock_irqsave(&vector_lock, flags);
- ret = assign_irq_vector_any_locked(irqd);
- raw_spin_unlock_irqrestore(&vector_lock, flags);
- return ret;
-}
-
static int
assign_irq_vector_policy(struct irq_data *irqd, struct irq_alloc_info *info)
{
@@ -276,10 +265,10 @@ assign_irq_vector_policy(struct irq_data
return reserve_managed_vector(irqd);
if (info->mask)
return assign_irq_vector(irqd, info->mask);
- if (info->type != X86_IRQ_ALLOC_TYPE_MSI &&
- info->type != X86_IRQ_ALLOC_TYPE_MSIX)
- return assign_irq_vector_any(irqd);
- /* For MSI(X) make only a global reservation with no guarantee */
+ /*
+ * Make only a global reservation with no guarantee. A real vector
+ * is associated at activation time.
+ */
return reserve_irq_vector(irqd);
}

@@ -456,13 +445,39 @@ static void x86_vector_free_irqs(struct
}
}

+static bool vector_configure_legacy(unsigned int virq, struct irq_data *irqd,
+ struct apic_chip_data *apicd)
+{
+ unsigned long flags;
+ bool realloc = false;
+
+ apicd->vector = ISA_IRQ_VECTOR(virq);
+ apicd->cpu = 0;
+ apicd->can_reserve = true;
+
+ raw_spin_lock_irqsave(&vector_lock, flags);
+ /*
+ * If the interrupt is activated, then it must stay at this vector
+ * position. That's usually the timer interrupt (0).
+ */
+ if (irqd_is_activated(irqd)) {
+ trace_vector_setup(virq, true, 0);
+ apic_update_irq_cfg(irqd, apicd->vector, apicd->cpu);
+ } else {
+ /* Release the vector */
+ clear_irq_vector(irqd);
+ realloc = true;
+ }
+ raw_spin_unlock_irqrestore(&vector_lock, flags);
+ return realloc;
+}
+
static int x86_vector_alloc_irqs(struct irq_domain *domain, unsigned int virq,
unsigned int nr_irqs, void *arg)
{
struct irq_alloc_info *info = arg;
struct apic_chip_data *apicd;
struct irq_data *irqd;
- unsigned long flags;
int i, err, node;

if (disable_apic)
@@ -496,13 +511,8 @@ static int x86_vector_alloc_irqs(struct
* config.
*/
if (info->flags & X86_IRQ_ALLOC_LEGACY) {
- apicd->vector = ISA_IRQ_VECTOR(virq + i);
- apicd->cpu = 0;
- trace_vector_setup(virq + i, true, 0);
- raw_spin_lock_irqsave(&vector_lock, flags);
- apic_update_irq_cfg(irqd, apicd->vector, apicd->cpu);
- raw_spin_unlock_irqrestore(&vector_lock, flags);
- continue;
+ if (!vector_configure_legacy(virq + i, irqd, apicd))
+ continue;
}

err = assign_irq_vector_policy(irqd, info);