powerpc/perf: Fix loop exit condition in nest_imc_event_init

The data structure (i.e struct imc_mem_info) to hold the memory address information for nest imc units is allocated based on the number of nodes in the system.

nest_imc_event_init() traverse this struct array to calculate the memory base address for the event-cpu. If we fail to find a match for the event cpu's chip-id in imc_mem_info struct array, then the do-while loop will iterate until we crash.

Fix this by changing the loop exit condition based on the number of nodes in the system.

---
 arch/powerpc/perf/imc-pmu.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

index 78514170cf71..e9dc771f3e3d 100644
@@ -459,7 +459,7 @@ static void nest_imc_counters_release(struct perf_event *event)
 
 static int nest_imc_event_init(struct perf_event *event)
 {
-	int chip_id, rc, node_id;
+	int chip_id, rc, node_id, nr_chips = num_possible_nodes();
 	u32 l_config, config = event->attr.config;
 	struct imc_mem_info *pcni;
 	struct imc_pmu *pmu;

@@ -508,7 +508,7 @@ static int nest_imc_event_init(struct perf_event *event)
 			break;
 		}
 		pcni++;
-	} while (pcni);
+	} while (--nr_chips);
 
 	if (!flag)
 		return -ENODEV;

2.17.1

Nest hardware counter memory resides in a per-chip reserve-memory. During nest_imc_event_init(), chip-id of the event-cpu is considered to calculate the base memory addresss for that cpu. Return, proper error condition if the chip_id calculated is invalid.

---
 arch/powerpc/perf/imc-pmu.c | 5 +++++
 1 file changed, 5 insertions(+)

index 6954636b16d1..78514170cf71 100644
@@ -496,6 +496,11 @@ static int nest_imc_event_init(struct perf_event *event)
 	 * Get the base memory addresss for this cpu.
 	 */
 	chip_id = cpu_to_chip_id(event->cpu);
+
+	/* Return, if chip_id is not valid */
+	if (chip_id < 0)
+		return -ENODEV;
+
 	pcni = pmu->mem_info;
 	do {
 		if (pcni->id == chip_id) {

2.17.1

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/a913e5e8b43be1d3897a141ce61c1ec0

cheers