On Thu, 24 Jul 2014 21:00:13 +0800, Hanjun Guo [off-list ref] wrote:

MADT contains the information for MPIDR which is essential for
SMP initialization, parse the GIC cpu interface structures to
get the MPIDR value and map it to cpu_logical_map(), and add
enabled cpu with valid MPIDR into cpu_possible_map and
cpu_present_map.

Signed-off-by: Hanjun Guo <redacted>
Signed-off-by: Tomasz Nowicki <redacted>
---
+	/* If it is the first CPU, no need to check duplicate MPIDRs */
+	if (!enabled_cpus)
+		goto skip_mpidr_check;
+
+	/*
+	 * Duplicate MPIDRs are a recipe for disaster. Scan
+	 * all initialized entries and check for
+	 * duplicates. If any is found just ignore the CPU.
+	 */
+	for_each_present_cpu(cpu) {
+		if (cpu_logical_map(cpu) == mpidr) {
+			pr_err("Firmware bug, duplicate CPU MPIDR: 0x%llx in MADT\n",
+			       mpidr);
+			return -EINVAL;
+		}
+	}
+
+skip_mpidr_check:
+	enabled_cpus++;

So, this hunk is embarrasing. The goto is completely unnecessary and the
whole for_each_present_cpu() block can be inside an
"if (enabled_cpus) { ... }" block. A goto is just nasty.

That said, is the if even necessary? Will for_each_present_cpu() iterate
over anything if it is processing the first cpu? (I don't actually know
the answer here, I did a quick look but not enough to get an
authoritative answer).

g.