linux-kernel - [PATCH] powerpc/pseries: start rtasd before PCI probing

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Message-ID: <146399210850.26372.5857516772891352049.stgit@bahia.huguette.org>
Date:	Mon, 23 May 2016 10:28:28 +0200
From:	Greg Kurz <gkurz@...ux.vnet.ibm.com>
To:	Michael Ellerman <mpe@...erman.id.au>
Cc:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Michael Roth <mdroth@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org, Paul Mackerras <paulus@...ba.org>,
	qemu-ppc@...gnu.org, linuxppc-dev@...ts.ozlabs.org,
	David Gibson <david@...son.dropbear.id.au>
Subject: [PATCH] powerpc/pseries: start rtasd before PCI probing

A strange behaviour is observed when comparing PCI hotplug in QEMU, between
x86 and pseries. If you consider the following steps:
- start a VM
- add a PCI device via the QEMU monitor before the rtasd has started (for
  example starting the VM in paused state, or hotplug during FW or boot
  loader)
- resume the VM execution

The x86 kernel detects the PCI device, but the pseries one does not.

This happens because the rtasd kernel worker is currently started under
device_initcall, while PCI probing happens earlier under subsys_initcall.

As a consequence, if we have a pending RTAS event at boot time, a message
is printed and the event is dropped.

This patch moves all the initialization of rtasd to arch_initcall, which is
run before subsys_call: this way, logging_enabled is true when the RTAS
event pops up and it is not lost anymore.

The proc fs bits stay at device_initcall because they cannot be run before
fs_initcall.

Signed-off-by: Greg Kurz <gkurz@...ux.vnet.ibm.com>
---
 arch/powerpc/kernel/rtasd.c |   19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/kernel/rtasd.c b/arch/powerpc/kernel/rtasd.c
index e864b7c5884e..ad9e4e1a2d5d 100644
--- a/arch/powerpc/kernel/rtasd.c
+++ b/arch/powerpc/kernel/rtasd.c
@@ -526,10 +526,8 @@ void rtas_cancel_event_scan(void)
 }
 EXPORT_SYMBOL_GPL(rtas_cancel_event_scan);
 
-static int __init rtas_init(void)
+static int __init rtas_event_scan_init(void)
 {
-	struct proc_dir_entry *entry;
-
 	if (!machine_is(pseries) && !machine_is(chrp))
 		return 0;
 
@@ -562,13 +560,24 @@ static int __init rtas_init(void)
 		return -ENOMEM;
 	}
 
+	start_event_scan();
+
+	return 0;
+}
+arch_initcall(rtas_event_scan_init);
+
+static int __init rtas_init(void)
+{
+	struct proc_dir_entry *entry;
+
+	if (!machine_is(pseries) && !machine_is(chrp))
+		return 0;
+
 	entry = proc_create("powerpc/rtas/error_log", S_IRUSR, NULL,
 			    &proc_rtas_log_operations);
 	if (!entry)
 		printk(KERN_ERR "Failed to create error_log proc entry\n");
 
-	start_event_scan();
-
 	return 0;
 }
 __initcall(rtas_init);