x86, irq: Allow 0xff for /proc/irq/[n]/smp_affinity on an 8-cpu system

John Blackwood reported:
> on an older Dell PowerEdge 6650 system with 8 cpus (4 are hyper-threaded),
> and  32 bit (x86) kernel, once you change the irq smp_affinity of an irq
> to be less than all cpus in the system, you can never change really the
> irq smp_affinity back to be all cpus in the system (0xff) again,
> even though no error status is returned on the "/bin/echo ff >
> /proc/irq/[n]/smp_affinity" operation.
>
> This is due to that fact that BAD_APICID has the same value as
> all cpus (0xff) on 32bit kernels, and thus the value returned from
> set_desc_affinity() via the cpu_mask_to_apicid_and() function is treated
> as a failure in set_ioapic_affinity_irq_desc(), and no affinity changes
> are made.

set_desc_affinity() is already checking if the incoming cpu mask
intersects with the cpu online mask or not. So there is no need
for the apic op cpu_mask_to_apicid_and() to check again
and return BAD_APICID.

Remove the BAD_APICID return value from cpu_mask_to_apicid_and()
and also fix set_desc_affinity() to return -1 instead of using BAD_APICID
to represent error conditions (as cpu_mask_to_apicid_and() can return
logical or physical apicid values and BAD_APICID is really to represent
bad physical apic id).

Reported-by: John Blackwood <john.blackwood@ccur.com>
Root-caused-by: John Blackwood <john.blackwood@ccur.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
LKML-Reference: <1261103386.2535.409.camel@sbs-t61>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

arch/x86/include/asm/hw_irq.h

@@ -103,7 +103,8 @@ extern int assign_irq_vector(int, struct irq_cfg *, const struct cpumask *);
 extern void send_cleanup_vector(struct irq_cfg *);
 
 struct irq_desc;
-extern unsigned int set_desc_affinity(struct irq_desc *, const struct cpumask *);
+extern unsigned int set_desc_affinity(struct irq_desc *, const struct cpumask *,
+				      unsigned int *dest_id);
 extern int IO_APIC_get_PCI_irq_vector(int bus, int devfn, int pin, struct io_apic_irq_attr *irq_attr);
 extern void setup_ioapic_dest(void);
 

arch/x86/kernel/apic/apic_flat_64.c

@@ -306,10 +306,7 @@ physflat_cpu_mask_to_apicid_and(const struct cpumask *cpumask,
 		if (cpumask_test_cpu(cpu, cpu_online_mask))
 			break;
 	}
-	if (cpu < nr_cpu_ids)
-		return per_cpu(x86_cpu_to_apicid, cpu);
-
-	return BAD_APICID;
+	return per_cpu(x86_cpu_to_apicid, cpu);
 }
 
 struct apic apic_physflat =  {

arch/x86/kernel/apic/bigsmp_32.c

@@ -131,10 +131,7 @@ static unsigned int bigsmp_cpu_mask_to_apicid_and(const struct cpumask *cpumask,
 		if (cpumask_test_cpu(cpu, cpu_online_mask))
 			break;
 	}
-	if (cpu < nr_cpu_ids)
-		return bigsmp_cpu_to_logical_apicid(cpu);
-
-	return BAD_APICID;
+	return bigsmp_cpu_to_logical_apicid(cpu);
 }
 
 static int bigsmp_phys_pkg_id(int cpuid_apic, int index_msb)

arch/x86/kernel/apic/io_apic.c

@@ -2276,26 +2276,28 @@ static void __target_IO_APIC_irq(unsigned int irq, unsigned int dest, struct irq
 
 /*
  * Either sets desc->affinity to a valid value, and returns
- * ->cpu_mask_to_apicid of that, or returns BAD_APICID and
+ * ->cpu_mask_to_apicid of that in dest_id, or returns -1 and
  * leaves desc->affinity untouched.
  */
 unsigned int
-set_desc_affinity(struct irq_desc *desc, const struct cpumask *mask)
+set_desc_affinity(struct irq_desc *desc, const struct cpumask *mask,
+		  unsigned int *dest_id)
 {
 	struct irq_cfg *cfg;
 	unsigned int irq;
 
 	if (!cpumask_intersects(mask, cpu_online_mask))
-		return BAD_APICID;
+		return -1;
 
 	irq = desc->irq;
 	cfg = desc->chip_data;
 	if (assign_irq_vector(irq, cfg, mask))
-		return BAD_APICID;
+		return -1;
 
 	cpumask_copy(desc->affinity, mask);
 
-	return apic->cpu_mask_to_apicid_and(desc->affinity, cfg->domain);
+	*dest_id = apic->cpu_mask_to_apicid_and(desc->affinity, cfg->domain);
+	return 0;
 }
 
 static int
@@ -2311,12 +2313,11 @@ set_ioapic_affinity_irq_desc(struct irq_desc *desc, const struct cpumask *mask)
 	cfg = desc->chip_data;
 
 	spin_lock_irqsave(&ioapic_lock, flags);
-	dest = set_desc_affinity(desc, mask);
-	if (dest != BAD_APICID) {
+	ret = set_desc_affinity(desc, mask, &dest);
+	if (!ret) {
 		/* Only the high 8 bits are valid. */
 		dest = SET_APIC_LOGICAL_ID(dest);
 		__target_IO_APIC_irq(irq, dest, cfg);
-		ret = 0;
 	}
 	spin_unlock_irqrestore(&ioapic_lock, flags);
 
@@ -3351,8 +3352,7 @@ static int set_msi_irq_affinity(unsigned int irq, const struct cpumask *mask)
 	struct msi_msg msg;
 	unsigned int dest;
 
-	dest = set_desc_affinity(desc, mask);
-	if (dest == BAD_APICID)
+	if (set_desc_affinity(desc, mask, &dest))
 		return -1;
 
 	cfg = desc->chip_data;
@@ -3384,8 +3384,7 @@ ir_set_msi_irq_affinity(unsigned int irq, const struct cpumask *mask)
 	if (get_irte(irq, &irte))
 		return -1;
 
-	dest = set_desc_affinity(desc, mask);
-	if (dest == BAD_APICID)
+	if (set_desc_affinity(desc, mask, &dest))
 		return -1;
 
 	irte.vector = cfg->vector;
@@ -3567,8 +3566,7 @@ static int dmar_msi_set_affinity(unsigned int irq, const struct cpumask *mask)
 	struct msi_msg msg;
 	unsigned int dest;
 
-	dest = set_desc_affinity(desc, mask);
-	if (dest == BAD_APICID)
+	if (set_desc_affinity(desc, mask, &dest))
 		return -1;
 
 	cfg = desc->chip_data;
@@ -3623,8 +3621,7 @@ static int hpet_msi_set_affinity(unsigned int irq, const struct cpumask *mask)
 	struct msi_msg msg;
 	unsigned int dest;
 
-	dest = set_desc_affinity(desc, mask);
-	if (dest == BAD_APICID)
+	if (set_desc_affinity(desc, mask, &dest))
 		return -1;
 
 	cfg = desc->chip_data;
@@ -3730,8 +3727,7 @@ static int set_ht_irq_affinity(unsigned int irq, const struct cpumask *mask)
 	struct irq_cfg *cfg;
 	unsigned int dest;
 
-	dest = set_desc_affinity(desc, mask);
-	if (dest == BAD_APICID)
+	if (set_desc_affinity(desc, mask, &dest))
 		return -1;
 
 	cfg = desc->chip_data;

arch/x86/kernel/apic/x2apic_cluster.c

@@ -148,10 +148,7 @@ x2apic_cpu_mask_to_apicid_and(const struct cpumask *cpumask,
 			break;
 	}
 
-	if (cpu < nr_cpu_ids)
-		return per_cpu(x86_cpu_to_logical_apicid, cpu);
-
-	return BAD_APICID;
+	return per_cpu(x86_cpu_to_logical_apicid, cpu);
 }
 
 static unsigned int x2apic_cluster_phys_get_apic_id(unsigned long x)

arch/x86/kernel/apic/x2apic_phys.c

@@ -146,10 +146,7 @@ x2apic_cpu_mask_to_apicid_and(const struct cpumask *cpumask,
 			break;
 	}
 
-	if (cpu < nr_cpu_ids)
-		return per_cpu(x86_cpu_to_apicid, cpu);
-
-	return BAD_APICID;
+	return per_cpu(x86_cpu_to_apicid, cpu);
 }
 
 static unsigned int x2apic_phys_get_apic_id(unsigned long x)

arch/x86/kernel/apic/x2apic_uv_x.c

@@ -225,10 +225,7 @@ uv_cpu_mask_to_apicid_and(const struct cpumask *cpumask,
 		if (cpumask_test_cpu(cpu, cpu_online_mask))
 			break;
 	}
-	if (cpu < nr_cpu_ids)
-		return per_cpu(x86_cpu_to_apicid, cpu);
-
-	return BAD_APICID;
+	return per_cpu(x86_cpu_to_apicid, cpu);
 }
 
 static unsigned int x2apic_get_apic_id(unsigned long x)

arch/x86/kernel/uv_irq.c

@@ -215,8 +215,7 @@ static int uv_set_irq_affinity(unsigned int irq, const struct cpumask *mask)
 	unsigned long mmr_offset;
 	unsigned mmr_pnode;
 
-	dest = set_desc_affinity(desc, mask);
-	if (dest == BAD_APICID)
+	if (set_desc_affinity(desc, mask, &dest))
 		return -1;
 
 	mmr_value = 0;