[IA64] SN: validate smp_affinity mask on intr redirect

On SN, only allow one bit to be set in the smp_affinty mask when
redirecting an interrupt.  Currently setting multiple bits is allowed, but
only the first bit is used in determining the CPU to redirect to.  This has
caused confusion among some customers.

[akpm@linux-foundation.org: fixes]
Signed-off-by: John Keller <jpk@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Tony Luck <tony.luck@intel.com>

arch/ia64/kernel/irq.c

@@ -104,6 +104,17 @@ void set_irq_affinity_info (unsigned int irq, int hwid, int redir)
 		irq_redir[irq] = (char) (redir & 0xff);
 	}
 }
+
+bool is_affinity_mask_valid(cpumask_t cpumask)
+{
+	if (ia64_platform_is("sn2")) {
+		/* Only allow one CPU to be specified in the smp_affinity mask */
+		if (cpus_weight(cpumask) != 1)
+			return false;
+	}
+	return true;
+}
+
 #endif /* CONFIG_SMP */
 
 #ifdef CONFIG_HOTPLUG_CPU

include/asm-ia64/irq.h

@@ -11,6 +11,9 @@
  * 02/29/00     D.Mosberger	moved most things into hw_irq.h
  */
 
+#include <linux/types.h>
+#include <linux/cpumask.h>
+
 #define NR_IRQS		256
 #define NR_IRQ_VECTORS	NR_IRQS
 
@@ -29,5 +32,8 @@ extern void disable_irq (unsigned int);
 extern void disable_irq_nosync (unsigned int);
 extern void enable_irq (unsigned int);
 extern void set_irq_affinity_info (unsigned int irq, int dest, int redir);
+bool is_affinity_mask_valid(cpumask_t cpumask);
+
+#define is_affinity_mask_valid is_affinity_mask_valid
 
 #endif /* _ASM_IA64_IRQ_H */

kernel/irq/proc.c

@@ -27,6 +27,10 @@ static int irq_affinity_read_proc(char *page, char **start, off_t off,
 	return len;
 }
 
+#ifndef is_affinity_mask_valid
+#define is_affinity_mask_valid(val) 1
+#endif
+
 int no_irq_affinity;
 static int irq_affinity_write_proc(struct file *file, const char __user *buffer,
 				   unsigned long count, void *data)
@@ -42,6 +46,9 @@ static int irq_affinity_write_proc(struct file *file, const char __user *buffer,
 	if (err)
 		return err;
 
+	if (!is_affinity_mask_valid(new_value))
+		return -EINVAL;
+
 	/*
 	 * Do not allow disabling IRQs completely - it's a too easy
 	 * way to make the system unusable accidentally :-) At least