Re: [PATCH v3 1/2] powerpc/powernv: Enhance opal message read interface

On 8/22/19 11:21 AM, Oliver O'Halloran wrote:

On Wed, 2019-08-21 at 13:43 +0530, Vasant Hegde wrote:

quoted

Use "opal-msg-size" device tree property to allocate memory for "opal_msg".

Cc: Mahesh Salgaonkar <redacted>
Cc: Jeremy Kerr <jk@ozlabs.org>
Signed-off-by: Vasant Hegde <redacted>
---
Changes in v3:
   - Call BUG_ON, if we fail to allocate memory during init.

-Vasant

  arch/powerpc/platforms/powernv/opal.c | 29 ++++++++++++++++++---------
  1 file changed, 19 insertions(+), 10 deletions(-)

diff --git a/arch/powerpc/platforms/powernv/opal.c b/arch/powerpc/platforms/powernv/opal.c
index aba443be7daa..4f1f68f568bf 100644
--- a/arch/powerpc/platforms/powernv/opal.c
+++ b/arch/powerpc/platforms/powernv/opal.c

@@ -58,6 +58,8 @@ static DEFINE_SPINLOCK(opal_write_lock);
  static struct atomic_notifier_head opal_msg_notifier_head[OPAL_MSG_TYPE_MAX];
  static uint32_t opal_heartbeat;
  static struct task_struct *kopald_tsk;
+static struct opal_msg *opal_msg;
+static uint64_t opal_msg_size;
  
  void opal_configure_cores(void)
  {

@@ -271,14 +273,9 @@ static void opal_message_do_notify(uint32_t msg_type, void *msg)
  static void opal_handle_message(void)
  {
  	s64 ret;
-	/*
-	 * TODO: pre-allocate a message buffer depending on opal-msg-size
-	 * value in /proc/device-tree.
-	 */
-	static struct opal_msg msg;
  	u32 type;
  
-	ret = opal_get_msg(__pa(&msg), sizeof(msg));
+	ret = opal_get_msg(__pa(opal_msg), opal_msg_size);
  	/* No opal message pending. */
  	if (ret == OPAL_RESOURCE)
  		return;

@@ -290,14 +287,14 @@ static void opal_handle_message(void)
  		return;
  	}
  
-	type = be32_to_cpu(msg.msg_type);
+	type = be32_to_cpu(opal_msg->msg_type);
  
  	/* Sanity check */
  	if (type >= OPAL_MSG_TYPE_MAX) {
  		pr_warn_once("%s: Unknown message type: %u\n", __func__, type);
  		return;
  	}
-	opal_message_do_notify(type, (void *)&msg);
+	opal_message_do_notify(type, (void *)opal_msg);
  }
  
  static irqreturn_t opal_message_notify(int irq, void *data)

@@ -306,9 +303,21 @@ static irqreturn_t opal_message_notify(int irq, void *data)
  	return IRQ_HANDLED;
  }
  
-static int __init opal_message_init(void)
+static int __init opal_message_init(struct device_node *opal_node)
  {
  	int ret, i, irq;

quoted

+	const __be32 *val;
+
+	val = of_get_property(opal_node, "opal-msg-size", NULL);
+	if (val)
+		opal_msg_size = be32_to_cpup(val);

Use of_property_read_u32()

Yes. Will fix it.

quoted

+
+	/* If opal-msg-size property is not available then use default size */
+	if (!opal_msg_size)
+		opal_msg_size = sizeof(struct opal_msg);
+
+	opal_msg = kmalloc(opal_msg_size, GFP_KERNEL);

quoted

+	BUG_ON(opal_msg == NULL);

Seems questionable. Why not fall back to using a staticly allocated
struct opal_msg? Or re-try the allocation with the size limited to
sizeof(struct opal_msg)?

If we are not able to allocate memory during init then we have bigger problem.
No point in continuing. Hence added BUG_ON().
May be I can retry allocation with fixed size before calling BUG_ON().
How about something like below :

+       /* If opal-msg-size property is not available then use default size */
+       if (!opal_msg_size)
+               opal_msg_size = sizeof(struct opal_msg);
+
+       opal_msg = kmalloc(opal_msg_size, GFP_KERNEL);
+       if (!opal_msg) {
+               opal_msg = kmalloc(sizeof(struct opal_msg), GFP_KERNEL);
+               BUG_ON(opal_msg == NULL);
+       }


-Vasant