powerpc/mce: Avoid using irq_work_queue() in realmode

In realmode mce handler we use irq_work_queue() to defer
the processing of mce events, irq_work_queue() can only
be called when translation is enabled because it touches
memory outside RMA, hence we enable translation before
calling irq_work_queue and disable on return, though it
is not safe to do in realmode.

To avoid this, program the decrementer and call the event
processing functions from timer handler.

Signed-off-by: Ganesh Goudar <ganeshgr@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220120121931.517974-1-ganeshgr@linux.ibm.com

3 files changed, 3 insertions, 31 deletions

diff --git a/arch/powerpc/platforms/pseries/pseries.h b/arch/powerpc/platforms/pseries/pseries.h
index 56c9ef9052e9..af162aeeae86 100644
--- a/arch/powerpc/platforms/pseries/pseries.h
+++ b/arch/powerpc/platforms/pseries/pseries.h
@@ -21,6 +21,7 @@ struct pt_regs;
 extern int pSeries_system_reset_exception(struct pt_regs *regs);
 extern int pSeries_machine_check_exception(struct pt_regs *regs);
 extern long pseries_machine_check_realmode(struct pt_regs *regs);
+void pSeries_machine_check_log_err(void);
 
 #ifdef CONFIG_SMP
 extern void smp_init_pseries(void);
diff --git a/arch/powerpc/platforms/pseries/ras.c b/arch/powerpc/platforms/pseries/ras.c
index 2a158e828c99..f12516c3998c 100644
--- a/arch/powerpc/platforms/pseries/ras.c
+++ b/arch/powerpc/platforms/pseries/ras.c
@@ -23,11 +23,6 @@ static DEFINE_SPINLOCK(ras_log_buf_lock);
 
 static int ras_check_exception_token;
 
-static void mce_process_errlog_event(struct irq_work *work);
-static struct irq_work mce_errlog_process_work = {
-	.func = mce_process_errlog_event,
-};
-
 #define EPOW_SENSOR_TOKEN	9
 #define EPOW_SENSOR_INDEX	0
 
@@ -745,7 +740,6 @@ static int mce_handle_error(struct pt_regs *regs, struct rtas_error_log *errp)
 	struct pseries_errorlog *pseries_log;
 	struct pseries_mc_errorlog *mce_log = NULL;
 	int disposition = rtas_error_disposition(errp);
-	unsigned long msr;
 	u8 error_type;
 
 	if (!rtas_error_extended(errp))
@@ -759,40 +753,16 @@ static int mce_handle_error(struct pt_regs *regs, struct rtas_error_log *errp)
 	error_type = mce_log->error_type;
 
 	disposition = mce_handle_err_realmode(disposition, error_type);
-
-	/*
-	 * Enable translation as we will be accessing per-cpu variables
-	 * in save_mce_event() which may fall outside RMO region, also
-	 * leave it enabled because subsequently we will be queuing work
-	 * to workqueues where again per-cpu variables accessed, besides
-	 * fwnmi_release_errinfo() crashes when called in realmode on
-	 * pseries.
-	 * Note: All the realmode handling like flushing SLB entries for
-	 *       SLB multihit is done by now.
-	 */
 out:
-	msr = mfmsr();
-	mtmsr(msr | MSR_IR | MSR_DR);
-
 	disposition = mce_handle_err_virtmode(regs, errp, mce_log,
 					      disposition);
-
-	/*
-	 * Queue irq work to log this rtas event later.
-	 * irq_work_queue uses per-cpu variables, so do this in virt
-	 * mode as well.
-	 */
-	irq_work_queue(&mce_errlog_process_work);
-
-	mtmsr(msr);
-
 	return disposition;
 }
 
 /*
  * Process MCE rtas errlog event.
  */
-static void mce_process_errlog_event(struct irq_work *work)
+void pSeries_machine_check_log_err(void)
 {
 	struct rtas_error_log *err;
 
diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c
index 83a04d967a59..069d7b3bb142 100644
--- a/arch/powerpc/platforms/pseries/setup.c
+++ b/arch/powerpc/platforms/pseries/setup.c
@@ -1086,6 +1086,7 @@ define_machine(pseries) {
 	.system_reset_exception = pSeries_system_reset_exception,
 	.machine_check_early	= pseries_machine_check_realmode,
 	.machine_check_exception = pSeries_machine_check_exception,
+	.machine_check_log_err	= pSeries_machine_check_log_err,
 #ifdef CONFIG_KEXEC_CORE
 	.machine_kexec          = pSeries_machine_kexec,
 	.kexec_cpu_down         = pseries_kexec_cpu_down,