[PATCH] x86/APIC: modify error_interrupt() to output using single printk()

[Elliott Mitchell <ehem+xen@xxxxxxx>]

This takes care of the issue of APIC errors tending to occur on multiple
cores at one.  In turn this tends to causes the error messages to be
merged together, making understanding them difficult.

Signed-off-by: Elliott Mitchell <ehem+xen@xxxxxxx>
---
 xen/arch/x86/apic.c | 22 +++++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)

diff --git a/xen/arch/x86/apic.c b/xen/arch/x86/apic.c
index f71474d47d..5399488120 100644
--- a/xen/arch/x86/apic.c
+++ b/xen/arch/x86/apic.c
@@ -1412,6 +1412,12 @@ static void cf_check error_interrupt(struct 
cpu_user_regs *regs)
     };
     unsigned int v, v1;
     int i;
+    char head[] = XENLOG_DEBUG "APIC error on CPU%u: %02x(%02x)";
+    char entry[] = ", %s";
+    /* header string, ", %s" for each potential entry, newline */
+    char fmt[sizeof(head) + ARRAY_SIZE(esr_fields) * (sizeof(entry) - 1) + 1];
+    const char *args[ARRAY_SIZE(esr_fields)];
+    unsigned int count = 0;
 
     /* First tickle the hardware, only then report what went on. -- REW */
     v = apic_read(APIC_ESR);
@@ -1419,12 +1425,18 @@ static void cf_check error_interrupt(struct 
cpu_user_regs *regs)
     v1 = apic_read(APIC_ESR);
     ack_APIC_irq();
 
-    printk(XENLOG_DEBUG "APIC error on CPU%u: %02x(%02x)",
-            smp_processor_id(), v , v1);
+    memcpy(fmt, head, sizeof(head) - 1);
+
     for ( i = 7; i >= 0; --i )
-        if ( v1 & (1 << i) )
-            printk(", %s", esr_fields[i]);
-    printk("\n");
+        if ( v1 & (1 << i) ) {
+            memcpy(fmt + sizeof(head) + (sizeof(entry) - 1) * count - 1, entry,
+                    sizeof(entry) - 1);
+            args[count++] = esr_fields[i];
+        }
+    memcpy(fmt + sizeof(head) + (sizeof(entry) - 1) * count - 1, "\n", 2);
+    /*_Static_assert(ARRAY_SIZE(args) == 8, "printk() here needs args 
added");*/
+    printk(fmt, smp_processor_id(), v , v1, args[0], args[1], args[2], args[3],
+            args[4], args[5], args[6], args[7]);
 }
 
 /*
-- 
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