During the removal of the idxd driver, registered offline callback is
invoked as part of the clean up process. However, on systems with only
one CPU online, no valid target is available to migrate the
perf context, resulting in a kernel oops:
BUG: unable to handle page fault for address: 000000000002a2b8
#PF: supervisor write access in kernel mode
#PF: error_code(0x0002) - not-present page
PGD 1470e1067 P4D 0
Oops: 0002 [#1] PREEMPT SMP NOPTI
CPU: 0 PID: 20 Comm: cpuhp/0 Not tainted 6.8.0-rc6-dsa+ #57
Hardware name: Intel Corporation AvenueCity/AvenueCity, BIOS BHSDCRB1.86B.2492.D03.2307181620 07/18/2023
RIP: 0010:mutex_lock+0x2e/0x50
...
Call Trace:
<TASK>
__die+0x24/0x70
page_fault_oops+0x82/0x160
do_user_addr_fault+0x65/0x6b0
__pfx___rdmsr_safe_on_cpu+0x10/0x10
exc_page_fault+0x7d/0x170
asm_exc_page_fault+0x26/0x30
mutex_lock+0x2e/0x50
mutex_lock+0x1e/0x50
perf_pmu_migrate_context+0x87/0x1f0
perf_event_cpu_offline+0x76/0x90 [idxd]
cpuhp_invoke_callback+0xa2/0x4f0
__pfx_perf_event_cpu_offline+0x10/0x10 [idxd]
cpuhp_thread_fun+0x98/0x150
smpboot_thread_fn+0x27/0x260
smpboot_thread_fn+0x1af/0x260
__pfx_smpboot_thread_fn+0x10/0x10
kthread+0x103/0x140
__pfx_kthread+0x10/0x10
ret_from_fork+0x31/0x50
__pfx_kthread+0x10/0x10
ret_from_fork_asm+0x1b/0x30
<TASK>
Fix the issue by preventing the migration of the perf context to an
invalid target.
Fixes: 81dd4d4d6178 ("dmaengine: idxd: Add IDXD performance monitor support")
Reported-by: Terrence Xu <terrence.xu@xxxxxxxxx>
Tested-by: Terrence Xu <terrence.xu@xxxxxxxxx>
Signed-off-by: Fenghua Yu <fenghua.yu@xxxxxxxxx>
---
drivers/dma/idxd/perfmon.c | 9 +++------
1 file changed, 3 insertions(+), 6 deletions(-)
diff --git a/drivers/dma/idxd/perfmon.c b/drivers/dma/idxd/perfmon.c
index fdda6d604262..5e94247e1ea7 100644
--- a/drivers/dma/idxd/perfmon.c
+++ b/drivers/dma/idxd/perfmon.c
@@ -528,14 +528,11 @@ static int perf_event_cpu_offline(unsigned int cpu, struct hlist_node *node)
return 0;
target = cpumask_any_but(cpu_online_mask, cpu);
-
/* migrate events if there is a valid target */
- if (target < nr_cpu_ids)
+ if (target < nr_cpu_ids) {
cpumask_set_cpu(target, &perfmon_dsa_cpu_mask);
- else
- target = -1;
-
- perf_pmu_migrate_context(&idxd_pmu->pmu, cpu, target);
+ perf_pmu_migrate_context(&idxd_pmu->pmu, cpu, target);
+ }
return 0;
}
--
2.37.1
