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x86: move dmar_table_init out of enable_IR

PATCH New Yinghai Lu 3 participants 6 messages Aug 17, 2009 1 message not in the archive x86

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Yinghai Lu

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#0 lore raw

PATCH 1/1 x86: move dmar_table_init out of enable_IR

on x2apic system, we got

[    1.818072] ------------[ cut here ]------------
[    1.820376] WARNING: at kernel/lockdep.c:2461
lockdep_trace_alloc+0xa5/0xe9()
[    1.835282] Hardware name: ASSY,
[    1.839006] Modules linked in:
[    1.841253] Pid: 1, comm: swapper Not tainted
2.6.31-rc5-tip-03926-g39aaa80-dirty #510
[    1.858056] Call Trace:
[    1.859913]  [<ffffffff810d13aa>] ? lockdep_trace_alloc+0xa5/0xe9
[    1.876270]  [<ffffffff81093f37>] warn_slowpath_common+0x8d/0xd0
[    1.879132]  [<ffffffff81093fa1>] warn_slowpath_null+0x27/0x3d
[    1.896823]  [<ffffffff810d13aa>] lockdep_trace_alloc+0xa5/0xe9
[    1.900659]  [<ffffffff810cf5a0>] ? lock_release_holdtime+0x2f/0x199
[    1.917188]  [<ffffffff81167a3c>] kmem_cache_alloc_notrace+0x42/0x111
[    1.922320]  [<ffffffff8106fe8c>] ? reserve_memtype+0x152/0x518
[    1.938137]  [<ffffffff8106f8b1>] ? pat_pagerange_is_ram+0x4a/0x91
[    1.941730]  [<ffffffff8106fe8c>] reserve_memtype+0x152/0x518
[    1.958115]  [<ffffffff8106ce62>] __ioremap_caller+0x1dd/0x30f
[    1.975507]  [<ffffffff81ce2c5c>] ? acpi_os_map_memory+0x2a/0x47
[    1.978987]  [<ffffffff8106d0fd>] ioremap_nocache+0x2a/0x40
[    2.031400]  [<ffffffff810d0364>] ? trace_hardirqs_off+0x20/0x36
[    2.036096]  [<ffffffff81ce2c5c>] acpi_os_map_memory+0x2a/0x47
[    2.046263]  [<ffffffff815cd642>] acpi_tb_verify_table+0x3d/0x85
[    2.050349]  [<ffffffff81d34af7>] ? _spin_unlock_irqrestore+0x50/0x76
[    2.067327]  [<ffffffff815ccad6>] acpi_get_table_with_size+0x64/0xd9
[    2.070860]  [<ffffffff81d34af7>] ? _spin_unlock_irqrestore+0x50/0x76
[    2.088000]  [<ffffffff825c88d5>] dmar_table_detect+0x33/0x70
[    2.092047]  [<ffffffff825c8a01>] dmar_table_init+0x43/0x428
[    2.106854]  [<ffffffff825a7537>] enable_IR+0x1c/0x8d
[    2.110256]  [<ffffffff825a7624>] enable_IR_x2apic+0x7c/0x19e
[    2.127139]  [<ffffffff825a4876>] native_smp_prepare_cpus+0x139/0x3b8
[    2.145175]  [<ffffffff8259678d>] kernel_init+0x71/0x1da
[    2.148913]  [<ffffffff8104305a>] child_rip+0xa/0x20
[    2.152349]  [<ffffffff810429fc>] ? restore_args+0x0/0x30
[    2.167931]  [<ffffffff8259671c>] ? kernel_init+0x0/0x1da
[    2.171671]  [<ffffffff81043050>] ? child_rip+0x0/0x20
[    2.187607] ---[ end trace a7919e7f17c0a725 ]---

Pallipadi, Venkatesh said

| Looks like the problem started with this commit
|
| commit ce69a784504222c3ab6f1b3c357d09ec5772127a
|Author: Gleb Natapov <[email protected]>
|Date:   Mon Jul 20 15:24:17 2009 +0300
|
|x86/apic: Enable x2APIC without interrupt remapping under KVM
|
|Before this commit, dmar_table_init() was getting called with interrupts
|enabled and after this commit, it is getting called with interrupts
|disabled.

so try to move out dmar_table_init out of that function.

Analyzed-by Venkatesh Pallipadi <[email protected]>
Signed-off-by Yinghai Lu <[email protected]>
---
 arch/x86/kernel/apic/apic.c |   22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)
arch/x86/kernel/apic/apic.c +13 -9
Index: linux-2.6/arch/x86/kernel/apic/apic.c
===================================================================
@@ -1365,14 +1365,6 @@ void enable_x2apic(void)
 int __init enable_IR(void)
 {
 #ifdef CONFIG_INTR_REMAP
-    int ret;
-
-    ret = dmar_table_init();
-    if (ret) {
-        pr_debug("dmar_table_init() failed with %d:\n", ret);
-        return 0;
-    }
-
     if (!intr_remapping_supported()) {
         pr_debug("intr-remapping not supported\n");
         return 0;

@@ -1400,6 +1392,14 @@ void __init enable_IR_x2apic(void)
     unsigned long flags;
     struct IO_APIC_route_entry **ioapic_entries = NULL;
     int ret, x2apic_enabled = 0;
+    int dmar_table_init_ret = 0;
+
+#ifdef CONFIG_INTR_REMAP
+    dmar_table_init_ret = dmar_table_init();
+    if (dmar_table_init_ret)
+        pr_debug("dmar_table_init() failed with %d:\n",
+                dmar_table_init_ret);
+#endif
 
     ioapic_entries = alloc_ioapic_entries();
     if (!ioapic_entries) {

@@ -1417,7 +1417,11 @@ void __init enable_IR_x2apic(void)
     mask_8259A();
     mask_IO_APIC_setup(ioapic_entries);
 
-    ret = enable_IR();
+    if (dmar_table_init_ret)
+        ret = 0;
+    else
+        ret = enable_IR();
+
     if (!ret) {
         /* IR is required if there is APIC ID > 255 even when running
          * under KVM

A message that is not in the archive (sent off-list or not yet received): [email protected]

#2 lore raw

PATCH 1/1 x86: move dmar_table_init out of enable_IR

on x2apic system, we got

[    1.818072] ------------[ cut here ]------------
[    1.820376] WARNING: at kernel/lockdep.c:2461 lockdep_trace_alloc+0xa5/0xe9()
[    1.835282] Hardware name: ASSY,
[    1.839006] Modules linked in:
[    1.841253] Pid: 1, comm: swapper Not tainted 2.6.31-rc5-tip-03926-g39aaa80-dirty #510
[    1.858056] Call Trace:
[    1.859913]  [<ffffffff810d13aa>] ? lockdep_trace_alloc+0xa5/0xe9
[    1.876270]  [<ffffffff81093f37>] warn_slowpath_common+0x8d/0xd0
[    1.879132]  [<ffffffff81093fa1>] warn_slowpath_null+0x27/0x3d
[    1.896823]  [<ffffffff810d13aa>] lockdep_trace_alloc+0xa5/0xe9
[    1.900659]  [<ffffffff810cf5a0>] ? lock_release_holdtime+0x2f/0x199
[    1.917188]  [<ffffffff81167a3c>] kmem_cache_alloc_notrace+0x42/0x111
[    1.922320]  [<ffffffff8106fe8c>] ? reserve_memtype+0x152/0x518
[    1.938137]  [<ffffffff8106f8b1>] ? pat_pagerange_is_ram+0x4a/0x91
[    1.941730]  [<ffffffff8106fe8c>] reserve_memtype+0x152/0x518
[    1.958115]  [<ffffffff8106ce62>] __ioremap_caller+0x1dd/0x30f
[    1.975507]  [<ffffffff81ce2c5c>] ? acpi_os_map_memory+0x2a/0x47
[    1.978987]  [<ffffffff8106d0fd>] ioremap_nocache+0x2a/0x40
[    2.031400]  [<ffffffff810d0364>] ? trace_hardirqs_off+0x20/0x36
[    2.036096]  [<ffffffff81ce2c5c>] acpi_os_map_memory+0x2a/0x47
[    2.046263]  [<ffffffff815cd642>] acpi_tb_verify_table+0x3d/0x85
[    2.050349]  [<ffffffff81d34af7>] ? _spin_unlock_irqrestore+0x50/0x76
[    2.067327]  [<ffffffff815ccad6>] acpi_get_table_with_size+0x64/0xd9
[    2.070860]  [<ffffffff81d34af7>] ? _spin_unlock_irqrestore+0x50/0x76
[    2.088000]  [<ffffffff825c88d5>] dmar_table_detect+0x33/0x70
[    2.092047]  [<ffffffff825c8a01>] dmar_table_init+0x43/0x428
[    2.106854]  [<ffffffff825a7537>] enable_IR+0x1c/0x8d
[    2.110256]  [<ffffffff825a7624>] enable_IR_x2apic+0x7c/0x19e
[    2.127139]  [<ffffffff825a4876>] native_smp_prepare_cpus+0x139/0x3b8
[    2.145175]  [<ffffffff8259678d>] kernel_init+0x71/0x1da
[    2.148913]  [<ffffffff8104305a>] child_rip+0xa/0x20
[    2.152349]  [<ffffffff810429fc>] ? restore_args+0x0/0x30
[    2.167931]  [<ffffffff8259671c>] ? kernel_init+0x0/0x1da
[    2.171671]  [<ffffffff81043050>] ? child_rip+0x0/0x20
[    2.187607] ---[ end trace a7919e7f17c0a725 ]---

Pallipadi, Venkatesh said

| Looks like the problem started with this commit
|
| commit ce69a784504222c3ab6f1b3c357d09ec5772127a
|Author: Gleb Natapov <[email protected]>
|Date:   Mon Jul 20 15:24:17 2009 +0300
|
|x86/apic: Enable x2APIC without interrupt remapping under KVM
|
|Before this commit, dmar_table_init() was getting called with interrupts
|enabled and after this commit, it is getting called with interrupts
|disabled.

so try to move out dmar_table_init out of that function.

Analyzed-by Venkatesh Pallipadi <[email protected]>
Signed-off-by Yinghai Lu <[email protected]>
---
 arch/x86/kernel/apic/apic.c |   22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)
arch/x86/kernel/apic/apic.c +13 -9
Index: linux-2.6/arch/x86/kernel/apic/apic.c
===================================================================
@@ -1365,14 +1365,6 @@ void enable_x2apic(void)
 int __init enable_IR(void)
 {
 #ifdef CONFIG_INTR_REMAP
-	int ret;
-
-	ret = dmar_table_init();
-	if (ret) {
-		pr_debug("dmar_table_init() failed with %d:\n", ret);
-		return 0;
-	}
-
 	if (!intr_remapping_supported()) {
 		pr_debug("intr-remapping not supported\n");
 		return 0;

@@ -1400,6 +1392,14 @@ void __init enable_IR_x2apic(void)
 	unsigned long flags;
 	struct IO_APIC_route_entry **ioapic_entries = NULL;
 	int ret, x2apic_enabled = 0;
+	int dmar_table_init_ret = 0;
+
+#ifdef CONFIG_INTR_REMAP
+	dmar_table_init_ret = dmar_table_init();
+	if (dmar_table_init_ret)
+		pr_debug("dmar_table_init() failed with %d:\n",
+				dmar_table_init_ret);
+#endif
 
 	ioapic_entries = alloc_ioapic_entries();
 	if (!ioapic_entries) {

@@ -1417,7 +1417,11 @@ void __init enable_IR_x2apic(void)
 	mask_8259A();
 	mask_IO_APIC_setup(ioapic_entries);
 
-	ret = enable_IR();
+	if (dmar_table_init_ret)
+		ret = 0;
+	else
+		ret = enable_IR();
+
 	if (!ret) {
 		/* IR is required if there is APIC ID > 255 even when running
 		 * under KVM
#3 lore raw
Quoted 25 lines · Yinghai Lu
---
 arch/x86/kernel/apic/apic.c |   22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)

Index: linux-2.6/arch/x86/kernel/apic/apic.c
===================================================================

arch/x86/kernel/apic/apic.c +0 -8
@@ -1365,14 +1365,6 @@ void enable_x2apic(void)
 int __init enable_IR(void)
 {
 #ifdef CONFIG_INTR_REMAP
-	int ret;
-
-	ret = dmar_table_init();
-	if (ret) {
-		pr_debug("dmar_table_init() failed with %d:\n", ret);
-		return 0;
-	}
-
 	if (!intr_remapping_supported()) {
 		pr_debug("intr-remapping not supported\n");
 		return 0;

@@ -1400,6 +1392,14 @@ void __init enable_IR_x2apic(void)
 	unsigned long flags;

arch/x86/kernel/apic/apic.c void __init enable_IR_x2apic(void) · line 1402

Quoted 10 lines
arch/x86/kernel/apic/apic.c +8 -0
 	struct IO_APIC_route_entry **ioapic_entries = NULL;
 	int ret, x2apic_enabled = 0;
+	int dmar_table_init_ret = 0;
+
+#ifdef CONFIG_INTR_REMAP
+	dmar_table_init_ret = dmar_table_init();
+	if (dmar_table_init_ret)
+		pr_debug("dmar_table_init() failed with %d:\n",
+				dmar_table_init_ret);
+#endif

We can remove this ifdef check, as dmar_table_init() already handles the !config_intr_remap

Also, at this error condition, we should simply return if the cpu has no x2apic support. There is no x2apic support and we failed to enable interrupt-remapping. No need to go further down.

thanks,
suresh

Quoted 17 lines
arch/x86/kernel/apic/apic.c +5 -1
 	ioapic_entries = alloc_ioapic_entries();
 	if (!ioapic_entries) {

@@ -1417,7 +1417,11 @@ void __init enable_IR_x2apic(void)
 	mask_8259A();
 	mask_IO_APIC_setup(ioapic_entries);
 
-	ret = enable_IR();
+	if (dmar_table_init_ret)
+		ret = 0;
+	else
+		ret = enable_IR();
+
 	if (!ret) {
 		/* IR is required if there is APIC ID > 255 even when running
 		 * under KVM
#4 lore raw
Quoted 40 lines · Suresh Siddha
Quoted 25 lines · Yinghai Lu
---
 arch/x86/kernel/apic/apic.c |   22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)

Index: linux-2.6/arch/x86/kernel/apic/apic.c
===================================================================

arch/x86/kernel/apic/apic.c +0 -8
@@ -1365,14 +1365,6 @@ void enable_x2apic(void)
 int __init enable_IR(void)
 {
 #ifdef CONFIG_INTR_REMAP
-	int ret;
-
-	ret = dmar_table_init();
-	if (ret) {
-		pr_debug("dmar_table_init() failed with %d:\n", ret);
-		return 0;
-	}
-
 	if (!intr_remapping_supported()) {
 		pr_debug("intr-remapping not supported\n");
 		return 0;

@@ -1400,6 +1392,14 @@ void __init enable_IR_x2apic(void)
 	unsigned long flags;

arch/x86/kernel/apic/apic.c void __init enable_IR_x2apic(void) · line 1402

Quoted 10 lines
arch/x86/kernel/apic/apic.c +8 -0
 	struct IO_APIC_route_entry **ioapic_entries = NULL;
 	int ret, x2apic_enabled = 0;
+	int dmar_table_init_ret = 0;
+
+#ifdef CONFIG_INTR_REMAP
+	dmar_table_init_ret = dmar_table_init();
+	if (dmar_table_init_ret)
+		pr_debug("dmar_table_init() failed with %d:\n",
+				dmar_table_init_ret);
+#endif

We can remove this ifdef check, as dmar_table_init() already handles the !config_intr_remap

Quoted 3 lines

Also, at this error condition, we should simply return if the cpu has no x2apic support. There is no x2apic support and we failed to enable interrupt-remapping. No need to go further down.

like this ?

---
 arch/x86/kernel/apic/apic.c |    9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)
arch/x86/kernel/apic/apic.c +3 -6
Index: linux-2.6/arch/x86/kernel/apic/apic.c
===================================================================
@@ -1392,14 +1392,11 @@ void __init enable_IR_x2apic(void)
 	unsigned long flags;
 	struct IO_APIC_route_entry **ioapic_entries = NULL;
 	int ret, x2apic_enabled = 0;
-	int dmar_table_init_ret = 0;
+	int dmar_table_init_ret;
 
-#ifdef CONFIG_INTR_REMAP
 	dmar_table_init_ret = dmar_table_init();
-	if (dmar_table_init_ret)
-		pr_debug("dmar_table_init() failed with %d:\n",
-				dmar_table_init_ret);
-#endif
+	if (dmar_table_init_ret && !x2apic_supported())
+		return;
 
 	ioapic_entries = alloc_ioapic_entries();
 	if (!ioapic_entries) {
#5 lore raw
Quoted 27 lines · Yinghai Lu
Quoted 7 lines · Suresh Siddha

We can remove this ifdef check, as dmar_table_init() already handles the !config_intr_remap

Also, at this error condition, we should simply return if the cpu has no x2apic support. There is no x2apic support and we failed to enable interrupt-remapping. No need to go further down.

like this ?

---
 arch/x86/kernel/apic/apic.c |    9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

Index: linux-2.6/arch/x86/kernel/apic/apic.c
===================================================================

arch/x86/kernel/apic/apic.c +1 -2
@@ -1392,14 +1392,11 @@ void __init enable_IR_x2apic(void)
 	unsigned long flags;
 	struct IO_APIC_route_entry **ioapic_entries = NULL;
 	int ret, x2apic_enabled = 0;
-	int dmar_table_init_ret = 0;
+	int dmar_table_init_ret;
 
-#ifdef CONFIG_INTR_REMAP

arch/x86/kernel/apic/apic.c void __init enable_IR_x2apic(void) · line 1402

Quoted 10 lines
arch/x86/kernel/apic/apic.c +2 -4
 	dmar_table_init_ret = dmar_table_init();
-	if (dmar_table_init_ret)
-		pr_debug("dmar_table_init() failed with %d:\n",
-				dmar_table_init_ret);
-#endif
+	if (dmar_table_init_ret && !x2apic_supported())
+		return;
 
 	ioapic_entries = alloc_ioapic_entries();
 	if (!ioapic_entries) {

Ack.

#6 lore raw

[tip:x86/apic] x86, apic: Move dmar_table_init() out of enable_IR()

In reply to Yinghai Lu
Commit-ID:  b7f42ab2e237f08a5bbcefa17473e80eb05e725c
Gitweb:     http://git.kernel.org/tip/b7f42ab2e237f08a5bbcefa17473e80eb05e725c
Author:     Yinghai Lu <[email protected]>
AuthorDate: Mon, 17 Aug 2009 11:19:40 -0700
Committer:  Ingo Molnar <[email protected]>
CommitDate: Mon, 17 Aug 2009 20:22:56 +0200

x86, apic: Move dmar_table_init() out of enable_IR()

On an x2apic system, we got:

[    1.818072] ------------[ cut here ]------------
[    1.820376] WARNING: at kernel/lockdep.c:2461 lockdep_trace_alloc+0xa5/0xe9()
[    1.835282] Hardware name: ASSY,
[    1.839006] Modules linked in:
[    1.841253] Pid: 1, comm: swapper Not tainted 2.6.31-rc5-tip-03926-g39aaa80-dirty #510
[    1.858056] Call Trace:
[    1.859913]  [<ffffffff810d13aa>] ? lockdep_trace_alloc+0xa5/0xe9
[    1.876270]  [<ffffffff81093f37>] warn_slowpath_common+0x8d/0xd0
[    1.879132]  [<ffffffff81093fa1>] warn_slowpath_null+0x27/0x3d
[    1.896823]  [<ffffffff810d13aa>] lockdep_trace_alloc+0xa5/0xe9
[    1.900659]  [<ffffffff810cf5a0>] ? lock_release_holdtime+0x2f/0x199
[    1.917188]  [<ffffffff81167a3c>] kmem_cache_alloc_notrace+0x42/0x111
[    1.922320]  [<ffffffff8106fe8c>] ? reserve_memtype+0x152/0x518
[    1.938137]  [<ffffffff8106f8b1>] ? pat_pagerange_is_ram+0x4a/0x91
[    1.941730]  [<ffffffff8106fe8c>] reserve_memtype+0x152/0x518
[    1.958115]  [<ffffffff8106ce62>] __ioremap_caller+0x1dd/0x30f
[    1.975507]  [<ffffffff81ce2c5c>] ? acpi_os_map_memory+0x2a/0x47
[    1.978987]  [<ffffffff8106d0fd>] ioremap_nocache+0x2a/0x40
[    2.031400]  [<ffffffff810d0364>] ? trace_hardirqs_off+0x20/0x36
[    2.036096]  [<ffffffff81ce2c5c>] acpi_os_map_memory+0x2a/0x47
[    2.046263]  [<ffffffff815cd642>] acpi_tb_verify_table+0x3d/0x85
[    2.050349]  [<ffffffff81d34af7>] ? _spin_unlock_irqrestore+0x50/0x76
[    2.067327]  [<ffffffff815ccad6>] acpi_get_table_with_size+0x64/0xd9
[    2.070860]  [<ffffffff81d34af7>] ? _spin_unlock_irqrestore+0x50/0x76
[    2.088000]  [<ffffffff825c88d5>] dmar_table_detect+0x33/0x70
[    2.092047]  [<ffffffff825c8a01>] dmar_table_init+0x43/0x428
[    2.106854]  [<ffffffff825a7537>] enable_IR+0x1c/0x8d
[    2.110256]  [<ffffffff825a7624>] enable_IR_x2apic+0x7c/0x19e
[    2.127139]  [<ffffffff825a4876>] native_smp_prepare_cpus+0x139/0x3b8
[    2.145175]  [<ffffffff8259678d>] kernel_init+0x71/0x1da
[    2.148913]  [<ffffffff8104305a>] child_rip+0xa/0x20
[    2.152349]  [<ffffffff810429fc>] ? restore_args+0x0/0x30
[    2.167931]  [<ffffffff8259671c>] ? kernel_init+0x0/0x1da
[    2.171671]  [<ffffffff81043050>] ? child_rip+0x0/0x20
[    2.187607] ---[ end trace a7919e7f17c0a725 ]---

Venkatesh Pallipadi said:

| Looks like the problem started with this commit
|
| commit ce69a784504222c3ab6f1b3c357d09ec5772127a
| Author: Gleb Natapov <[email protected]>
| Date:   Mon Jul 20 15:24:17 2009 +0300
|
| x86/apic: Enable x2APIC without interrupt remapping under KVM
|
| Before this commit, dmar_table_init() was getting called
| with interrupts enabled and after this commit, it is getting
| called with interrupts disabled.

so try to move out dmar_table_init out of that function.

Analyzed-by Venkatesh Pallipadi <[email protected]>
Signed-off-by Yinghai Lu <[email protected]>
Cc Peter Zijlstra <[email protected]>
Cc Gleb Natapov <[email protected]>
Cc Suresh Siddha <[email protected]>
Cc "Pallipadi, Venkatesh" <[email protected]>

LKML-Reference: <[email protected]>

Signed-off-by Ingo Molnar <[email protected]>
---
 arch/x86/kernel/apic/apic.c |   22 +++++++++++++---------
 1 files changed, 13 insertions(+), 9 deletions(-)
arch/x86/kernel/apic/apic.c +13 -9
index de039fc..3fc3a6c 100644
@@ -1365,14 +1365,6 @@ void enable_x2apic(void)
 int __init enable_IR(void)
 {
 #ifdef CONFIG_INTR_REMAP
-	int ret;
-
-	ret = dmar_table_init();
-	if (ret) {
-		pr_debug("dmar_table_init() failed with %d:\n", ret);
-		return 0;
-	}
-
 	if (!intr_remapping_supported()) {
 		pr_debug("intr-remapping not supported\n");
 		return 0;

@@ -1400,6 +1392,14 @@ void __init enable_IR_x2apic(void)
 	unsigned long flags;
 	struct IO_APIC_route_entry **ioapic_entries = NULL;
 	int ret, x2apic_enabled = 0;
+	int dmar_table_init_ret = 0;
+
+#ifdef CONFIG_INTR_REMAP
+	dmar_table_init_ret = dmar_table_init();
+	if (dmar_table_init_ret)
+		pr_debug("dmar_table_init() failed with %d:\n",
+				dmar_table_init_ret);
+#endif
 
 	ioapic_entries = alloc_ioapic_entries();
 	if (!ioapic_entries) {

@@ -1417,7 +1417,11 @@ void __init enable_IR_x2apic(void)
 	mask_8259A();
 	mask_IO_APIC_setup(ioapic_entries);
 
-	ret = enable_IR();
+	if (dmar_table_init_ret)
+		ret = 0;
+	else
+		ret = enable_IR();
+
 	if (!ret) {
 		/* IR is required if there is APIC ID > 255 even when running
 		 * under KVM