[PATCH 2/2] x86, x2apic: limit the vector reservation to the user specified mask

[Suresh Siddha <suresh.b.siddha@intel.com>]

For the x2apic cluster mode, vector for an interrupt is currently reserved on
all the cpu's that are part of the x2apic cluster. But the interrupts will
be routed only to the cluster (derived from the first cpu in the mask) members
specified in the mask. So there is no need to reserve the vector in the unused
cluster members.

Modify __assign_irq_vector() to reserve the vectors based on the user
specified irq destination mask and the corresponding vector domain specified
by the apic driver.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
---
 arch/x86/include/asm/apic.h           |   14 +++++++++---
 arch/x86/kernel/apic/apic_noop.c      |    5 +++-
 arch/x86/kernel/apic/io_apic.c        |   36 ++++++++++++++++++++++-----------
 arch/x86/kernel/apic/x2apic_cluster.c |    8 ++++--
 4 files changed, 43 insertions(+), 20 deletions(-)

diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
index b37fa12..7746acb 100644
--- a/arch/x86/include/asm/apic.h
+++ b/arch/x86/include/asm/apic.h
@@ -306,7 +306,9 @@ struct apic {
 	unsigned long (*check_apicid_used)(physid_mask_t *map, int apicid);
 	unsigned long (*check_apicid_present)(int apicid);
 
-	void (*vector_allocation_domain)(int cpu, struct cpumask *retmask);
+	void (*vector_allocation_domain)(const struct cpumask *mask,
+					 struct cpumask *retmask,
+					 const struct cpumask *prevmask);
 	void (*init_apic_ldr)(void);
 
 	void (*ioapic_phys_id_map)(physid_mask_t *phys_map, physid_mask_t *retmap);
@@ -615,7 +617,9 @@ default_cpu_mask_to_apicid_and(const struct cpumask *cpumask,
 			       unsigned int *apicid);
 
 static inline void
-flat_vector_allocation_domain(int cpu, struct cpumask *retmask)
+flat_vector_allocation_domain(const struct cpumask *mask,
+			      struct cpumask *retmask,
+			      const struct cpumask *prevmask)
 {
 	/* Careful. Some cpus do not strictly honor the set of cpus
 	 * specified in the interrupt destination when using lowest
@@ -630,9 +634,11 @@ flat_vector_allocation_domain(int cpu, struct cpumask *retmask)
 }
 
 static inline void
-default_vector_allocation_domain(int cpu, struct cpumask *retmask)
+default_vector_allocation_domain(const struct cpumask *mask,
+				 struct cpumask *retmask,
+				 const struct cpumask *prevmask)
 {
-	cpumask_copy(retmask, cpumask_of(cpu));
+	cpumask_copy(retmask, cpumask_of(cpumask_first(retmask)));
 }
 
 static inline unsigned long default_check_apicid_used(physid_mask_t *map, int apicid)
diff --git a/arch/x86/kernel/apic/apic_noop.c b/arch/x86/kernel/apic/apic_noop.c
index 08c337b..847ece1 100644
--- a/arch/x86/kernel/apic/apic_noop.c
+++ b/arch/x86/kernel/apic/apic_noop.c
@@ -100,8 +100,11 @@ static unsigned long noop_check_apicid_present(int bit)
 	return physid_isset(bit, phys_cpu_present_map);
 }
 
-static void noop_vector_allocation_domain(int cpu, struct cpumask *retmask)
+static void noop_vector_allocation_domain(const struct cpumask *mask,
+					  struct cpumask *retmask,
+					  const struct cpumask *prevmask)
 {
+	int cpu = cpumask_first(retmask);
 	if (cpu != 0)
 		pr_warning("APIC: Vector allocated for non-BSP cpu\n");
 	cpumask_copy(retmask, cpumask_of(cpu));
diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index 7a945f8..0a55eb8 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -1097,6 +1097,22 @@ void unlock_vector_lock(void)
 	raw_spin_unlock(&vector_lock);
 }
 
+/*
+ * New cpu mask using the vector is a subset of the current in use mask.
+ * So cleanup the vector allocation for the members that are not used anymore.
+ */
+static inline int
+cleanup_unused_subset(struct cpumask *mask, struct irq_cfg *cfg)
+{
+	if (!cpumask_equal(mask, cfg->domain)) {
+		cpumask_andnot(cfg->old_domain, cfg->domain, mask);
+		cfg->move_in_progress = 1;
+		cpumask_and(cfg->domain, cfg->domain, mask);
+	}
+	free_cpumask_var(mask);
+	return 0;
+}
+
 static int
 __assign_irq_vector(int irq, struct irq_cfg *cfg, const struct cpumask *mask)
 {
@@ -1126,10 +1142,9 @@ __assign_irq_vector(int irq, struct irq_cfg *cfg, const struct cpumask *mask)
 	old_vector = cfg->vector;
 	if (old_vector) {
 		cpumask_and(tmp_mask, mask, cpu_online_mask);
-		if (cpumask_subset(tmp_mask, cfg->domain)) {
-			free_cpumask_var(tmp_mask);
-			return 0;
-		}
+		apic->vector_allocation_domain(mask, tmp_mask, cfg->domain);
+		if (cpumask_subset(tmp_mask, cfg->domain))
+			return cleanup_unused_subset(tmp_mask, cfg);
 	}
 
 	/* Only try and allocate irqs on cpus that are present */
@@ -1137,15 +1152,12 @@ __assign_irq_vector(int irq, struct irq_cfg *cfg, const struct cpumask *mask)
 	cpumask_clear(cfg->old_domain);
 	cpu = cpumask_first_and(mask, cpu_online_mask);
 	while (cpu < nr_cpu_ids) {
-		int new_cpu;
-		int vector, offset;
+		int new_cpu, vector, offset;
 
-		apic->vector_allocation_domain(cpu, tmp_mask);
-
-		if (cpumask_subset(tmp_mask, cfg->domain)) {
-			free_cpumask_var(tmp_mask);
-			return 0;
-		}
+		cpumask_copy(tmp_mask, cpumask_of(cpu));
+		apic->vector_allocation_domain(mask, tmp_mask, cfg->domain);
+		if (cpumask_subset(tmp_mask, cfg->domain))
+			return cleanup_unused_subset(tmp_mask, cfg);
 
 		vector = current_vector;
 		offset = current_offset;
diff --git a/arch/x86/kernel/apic/x2apic_cluster.c b/arch/x86/kernel/apic/x2apic_cluster.c
index b5d889b..4d49512 100644
--- a/arch/x86/kernel/apic/x2apic_cluster.c
+++ b/arch/x86/kernel/apic/x2apic_cluster.c
@@ -212,10 +212,12 @@ static int x2apic_cluster_probe(void)
 /*
  * Each x2apic cluster is an allocation domain.
  */
-static void cluster_vector_allocation_domain(int cpu, struct cpumask *retmask)
+static void cluster_vector_allocation_domain(const struct cpumask *mask,
+					     struct cpumask *retmask,
+					     const struct cpumask *prevmask)
 {
-	cpumask_clear(retmask);
-	cpumask_copy(retmask, per_cpu(cpus_in_cluster, cpu));
+	int cpu = cpumask_first(retmask);
+	cpumask_and(retmask, mask, per_cpu(cpus_in_cluster, cpu));
 }
 
 static struct apic apic_x2apic_cluster = {
-- 
1.7.6.5