cxl: Only check pid for userspace contexts

We only need to check the pid attached to this context for userspace contexts.
Kernel contexts can skip this check.
Signed-off-by: Michael Neuling <mikey@neuling.org>
Acked-by: Ian Munsie <imunsie@au1.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

drivers/misc/cxl/fault.c

@@ -172,8 +172,8 @@ void cxl_handle_fault(struct work_struct *fault_work)
 		container_of(fault_work, struct cxl_context, fault_work);
 	u64 dsisr = ctx->dsisr;
 	u64 dar = ctx->dar;
-	struct task_struct *task;
-	struct mm_struct *mm;
+	struct task_struct *task = NULL;
+	struct mm_struct *mm = NULL;
 
 	if (cxl_p2n_read(ctx->afu, CXL_PSL_DSISR_An) != dsisr ||
 	    cxl_p2n_read(ctx->afu, CXL_PSL_DAR_An) != dar ||
@@ -194,17 +194,19 @@ void cxl_handle_fault(struct work_struct *fault_work)
 	pr_devel("CXL BOTTOM HALF handling fault for afu pe: %i. "
 		"DSISR: %#llx DAR: %#llx\n", ctx->pe, dsisr, dar);
 
-	if (!(task = get_pid_task(ctx->pid, PIDTYPE_PID))) {
-		pr_devel("cxl_handle_fault unable to get task %i\n",
-			 pid_nr(ctx->pid));
-		cxl_ack_ae(ctx);
-		return;
-	}
-	if (!(mm = get_task_mm(task))) {
-		pr_devel("cxl_handle_fault unable to get mm %i\n",
-			 pid_nr(ctx->pid));
-		cxl_ack_ae(ctx);
-		goto out;
+	if (!ctx->kernel) {
+		if (!(task = get_pid_task(ctx->pid, PIDTYPE_PID))) {
+			pr_devel("cxl_handle_fault unable to get task %i\n",
+				 pid_nr(ctx->pid));
+			cxl_ack_ae(ctx);
+			return;
+		}
+		if (!(mm = get_task_mm(task))) {
+			pr_devel("cxl_handle_fault unable to get mm %i\n",
+				 pid_nr(ctx->pid));
+			cxl_ack_ae(ctx);
+			goto out;
+		}
 	}
 
 	if (dsisr & CXL_PSL_DSISR_An_DS)
@@ -214,9 +216,11 @@ void cxl_handle_fault(struct work_struct *fault_work)
 	else
 		WARN(1, "cxl_handle_fault has nothing to handle\n");
 
-	mmput(mm);
+	if (mm)
+		mmput(mm);
 out:
-	put_task_struct(task);
+	if (task)
+		put_task_struct(task);
 }
 
 static void cxl_prefault_one(struct cxl_context *ctx, u64 ea)