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qubes-linux-kernel/0002-mce-hide-EBUSY-initial...

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From a58197258286cf8dce45cf03b3b2b436b3cf8a99 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marek=20Marczykowski-G=C3=B3recki?=
<marmarek@invisiblethingslab.com>
Date: Tue, 5 Jan 2016 02:44:04 +0100
Subject: [PATCH] mce: hide EBUSY initialization error on Xen
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
In case of Xen, the device is already registered by xen mcelog (in
xen_late_init_mcelog), so fail here is expected. Note that
mcheck_init_device call is still expected to initialize mce_device. Comment
from threshold_init_device explaining the situation:
/*
* there are 3 funcs which need to be _initcalled in a logic sequence:
* 1. xen_late_init_mcelog
* 2. mcheck_init_device
* 3. threshold_init_device
*
* xen_late_init_mcelog must register xen_mce_chrdev_device before
* native mce_chrdev_device registration if running under xen platform;
*
* mcheck_init_device should be inited before threshold_init_device to
* initialize mce_device, otherwise a NULL ptr dereference will cause panic.
*
* so we use following _initcalls
* 1. device_initcall(xen_late_init_mcelog);
* 2. device_initcall_sync(mcheck_init_device);
* 3. late_initcall(threshold_init_device);
*
* when running under xen, the initcall order is 1,2,3;
* on baremetal, we skip 1 and we do only 2 and 3.
*/
Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
---
arch/x86/kernel/cpu/mce/core.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index 743370ee4983..3af7521b2279 100644
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -51,6 +51,10 @@
#include <asm/msr.h>
#include <asm/reboot.h>
+#ifdef CONFIG_XEN_MCE_LOG
+#include <xen/xen.h>
+#endif
+
#include "internal.h"
static DEFINE_MUTEX(mce_log_mutex);
@@ -2464,6 +2468,11 @@ static __init int mcheck_init_device(void)
free_cpumask_var(mce_device_initialized);
err_out:
+#ifdef CONFIG_XEN_MCE_LOG
+ /* in case of Xen, the character device was already registered, so do not
+ * treat this as an error */
+ if (!xen_initial_domain() || err != -EBUSY)
+#endif
pr_err("Unable to init MCE device (rc: %d)\n", err);
return err;
--
2.21.0