core/cpu: HID update race

If the per-core HID register is updated concurrently by multiple
threads, updates can get lost. This has been observed during fast
reboot where the HILE bit does not get cleared on all cores, which
can cause machine check exception interrupts to crash.

Fix this by only updating HID on thread0.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Stewart Smith <stewart@linux.ibm.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/core/cpu.c b/core/cpu.c
index a0ed1c5..1542776 100644
--- a/core/cpu.c
+++ b/core/cpu.c
@@ -1246,8 +1246,8 @@ void cpu_callin(struct cpu_thread *cpu)
 	sync();
 
 	cpu->job_has_no_return = false;
-
-	init_hid();
+	if (cpu_is_thread0(cpu))
+		init_hid();
 }
 
 static void opal_start_thread_job(void *data)