[PATCH v4 0/5] x86/apic: Fix restoring boot irq mode in reboot and kexec/kdump

[PATCH v4 0/5] x86/apic: Fix restoring boot irq mode in reboot and kexec/kdump

[Baoquan He]

This is v4 post. Only patch 0002 is updated.

A regression bug was introduced in below commit.
commit 522e66464467 ("x86/apic: Disable I/O APIC before shutdown of the local APIC")

It caused the action to fail which we try to restore boot irq mode
in reboot and kexec/kdump. Details can be seen in patch 0002.

Warning can always be seen during kdump kernel boot on qemu/kvm
platform. Our customer even saw casual kdump kernel hang once in
~30 attempts during stress testing of kdump on KVM machine.

v3->v4:
  Eric pointed out that in patch 0002 the change related to
  KEXEC_JUMP is not right.
  Correct it.

  Add Fixes tag and Cc to stable.

v2->v3:
  Change as Eric suggested:

  Rerrange patches and change code and messy function/variable naming.
  Change patch subject and log to make it more understandable. 

Baoquan He (5):
  x86/apic: Split out restore_boot_irq_mode from disable_IO_APIC
  x86/apic: Fix restoring boot irq mode in reboot and kexec/kdump
  x86/apic: Remove useless disable_IO_APIC
  x86/apic: Rename variable/function related to x86_io_apic_ops
  x86/apic: Set up through-local-APIC on boot CPU if 'noapic' specified

 arch/x86/include/asm/io_apic.h     |  9 +++++----
 arch/x86/include/asm/x86_init.h    |  8 ++++----
 arch/x86/kernel/apic/apic.c        |  2 +-
 arch/x86/kernel/apic/io_apic.c     | 16 ++++------------
 arch/x86/kernel/crash.c            |  3 ++-
 arch/x86/kernel/machine_kexec_32.c |  8 ++++----
 arch/x86/kernel/machine_kexec_64.c |  8 ++++----
 arch/x86/kernel/reboot.c           |  3 ++-
 arch/x86/kernel/x86_init.c         |  6 +++---
 arch/x86/xen/apic.c                |  2 +-
 drivers/iommu/irq_remapping.c      |  4 ++--
 11 files changed, 32 insertions(+), 37 deletions(-)

-- 
2.13.6

[PATCH v4 1/5] x86/apic: Split out restore_boot_irq_mode from disable_IO_APIC

[Baoquan He]

This is a preparation patch. Split out the code which restores boot
irq mode from disable_IO_APIC() and wrap into a new function
restore_boot_irq_mode(). No functional change.

Signed-off-by: Baoquan He <bhe@redhat.com>
---
 arch/x86/include/asm/io_apic.h | 1 +
 arch/x86/kernel/apic/io_apic.c | 5 +++++
 2 files changed, 6 insertions(+)

diff --git a/arch/x86/include/asm/io_apic.h b/arch/x86/include/asm/io_apic.h
index a8834dd546cd..558d1a6a13ad 100644
--- a/arch/x86/include/asm/io_apic.h
+++ b/arch/x86/include/asm/io_apic.h
@@ -193,6 +193,7 @@ static inline unsigned int io_apic_read(unsigned int apic, unsigned int reg)
 extern void setup_IO_APIC(void);
 extern void enable_IO_APIC(void);
 extern void disable_IO_APIC(void);
+extern void restore_boot_irq_mode(void);
 extern int IO_APIC_get_PCI_irq_vector(int bus, int devfn, int pin);
 extern void print_IO_APICs(void);
 #else  /* !CONFIG_X86_IO_APIC */
diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index 8ad2e410974f..7b73b6b9b4b6 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -1448,6 +1448,11 @@ void disable_IO_APIC(void)
 	 */
 	clear_IO_APIC();
 
+	restore_boot_irq_mode();
+}
+
+void restore_boot_irq_mode(void)
+{
 	if (!nr_legacy_irqs())
 		return;
 
-- 
2.13.6

[PATCH v4 2/5] x86/apic: Fix restoring boot irq mode in reboot and kexec/kdump

[Baoquan He]

This is a regression fix.

Before, to fix erratum AVR31, commit 522e66464467 ("x86/apic: Disable
I/O APIC before shutdown of the local APIC") moved lapic_shutdown()
calling after disable_IO_APIC() in reboot and kexec/kdump code path.
This introdued a regression. The root cause is that disable_IO_APIC()
not only clears IO_APIC, also restore boot irq mode by setting
LAPIC/APIC/IMCR, calling lapic_shutdown() after disable_IO_APIC() will
disable LAPIC and ruin the possible virtual wire mode setting which
the code has been trying to do all along.

The consequence is, in KVM guest kernel always prints warning as below
during kexec/kdump kernel boots up. That happened in setup_local_APIC()
since 'do { xxx } while (queued && max_loops > 0)' loop does not function
well any more if pending irq exists in APIC IRR after LAPIC is disabled.

[    0.001000] WARNING: CPU: 0 PID: 0 at arch/x86/kernel/apic/apic.c:1467 setup_local_APIC+0x228/0x330
[    0.001000] Modules linked in:
[    0.001000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.15.0-rc5+ #3
[    0.001000] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1.fc26 04/01/2014
[    0.001000] RIP: 0010:setup_local_APIC+0x228/0x330
[    0.001000] RSP: 0000:ffffffffb6e03eb8 EFLAGS: 00010286
[    0.001000] RAX: 0000009edb4c4d84 RBX: 0000000000000000 RCX: 00000000b099d800
[    0.001000] RDX: 0000009e00000000 RSI: 0000000000000000 RDI: 0000000000000810
[    0.001000] RBP: 0000000000000000 R08: ffffffffffffffff R09: 0000000000000001
[    0.001000] R10: ffff98ce6a801c00 R11: 0761076d072f0776 R12: 0000000000000001
[    0.001000] R13: 00000000000000f0 R14: 0000000000004000 R15: ffffffffffffc6ff
[    0.001000] FS:  0000000000000000(0000) GS:ffff98ce6bc00000(0000) knlGS:0000000000000000
[    0.001000] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    0.001000] CR2: 00000000ffffffff CR3: 0000000022209000 CR4: 00000000000406b0
[    0.001000] Call Trace:
[    0.001000]  apic_bsp_setup+0x56/0x74
[    0.001000]  x86_late_time_init+0x11/0x16
[    0.001000]  start_kernel+0x3c9/0x486
[    0.001000]  secondary_startup_64+0xa5/0xb0
[    0.001000] Code: 00 85 c9 74 2d 0f 31 c1 e1 0a 48 c1 e2 20 41 89 cf 4c 03 7c 24 08 48 09 d0 49 29 c7 4c 89 3c 24 48 83 3c 24 00 0f 8f 8f fe ff
ff <0f> ff e9 10 ff ff ff 48 83 2c 24 01 eb e7 48 83 c4 18 5b 5d 41
[    0.001000] ---[ end trace b88e71b9a6ebebdd ]---
[    0.001000] masked ExtINT on CPU#0

To fix this, just break down disable_IO_APIC(), then call
clear_IO_APIC() to stop IO_APIC where disable_IO_APIC() was called,
and call restore_boot_irq_mode() to restore boot irq mode before
reboot or kexec/kdump jump.

As for KEXEC_JUMP, it's a little different then reboot and kexec/kdump.
It doesn't call lapic_shutdown() before jump, so is not impacted by
commit 522e66464467. Here in order to keep it the same as the old code,
replace the old disable_IO_APIC() with clear_IO_APIC() and
restore_boot_irq_mode().

Signed-off-by: Baoquan He <bhe@redhat.com>
Fixes: commit 522e66464467 ("x86/apic: Disable I/O APIC before shutdown of the local APIC") 
Cc: stable@vger.kernel.org
---
v4->v3:
  Eric pointed out the change related to KEXEC_JUMP is not right.
  Correct it.

  Add Fixes tag and Cc to stable.

 arch/x86/include/asm/io_apic.h     | 1 +
 arch/x86/kernel/apic/io_apic.c     | 2 +-
 arch/x86/kernel/crash.c            | 3 ++-
 arch/x86/kernel/machine_kexec_32.c | 3 ++-
 arch/x86/kernel/machine_kexec_64.c | 3 ++-
 arch/x86/kernel/reboot.c           | 3 ++-
 6 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/io_apic.h b/arch/x86/include/asm/io_apic.h
index 558d1a6a13ad..0fa95bfacb39 100644
--- a/arch/x86/include/asm/io_apic.h
+++ b/arch/x86/include/asm/io_apic.h
@@ -193,6 +193,7 @@ static inline unsigned int io_apic_read(unsigned int apic, unsigned int reg)
 extern void setup_IO_APIC(void);
 extern void enable_IO_APIC(void);
 extern void disable_IO_APIC(void);
+extern void clear_IO_APIC(void);
 extern void restore_boot_irq_mode(void);
 extern int IO_APIC_get_PCI_irq_vector(int bus, int devfn, int pin);
 extern void print_IO_APICs(void);
diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index 7b73b6b9b4b6..2d7cd2db77f5 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -587,7 +587,7 @@ static void clear_IO_APIC_pin(unsigned int apic, unsigned int pin)
 		       mpc_ioapic_id(apic), pin);
 }
 
-static void clear_IO_APIC (void)
+void clear_IO_APIC (void)
 {
 	int apic, pin;
 
diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index 10e74d4778a1..1f6680427ff0 100644
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -199,9 +199,10 @@ void native_machine_crash_shutdown(struct pt_regs *regs)
 #ifdef CONFIG_X86_IO_APIC
 	/* Prevent crash_kexec() from deadlocking on ioapic_lock. */
 	ioapic_zap_locks();
-	disable_IO_APIC();
+	clear_IO_APIC();
 #endif
 	lapic_shutdown();
+	restore_boot_irq_mode();
 #ifdef CONFIG_HPET_TIMER
 	hpet_disable();
 #endif
diff --git a/arch/x86/kernel/machine_kexec_32.c b/arch/x86/kernel/machine_kexec_32.c
index edfede768688..4cd79d88a4ac 100644
--- a/arch/x86/kernel/machine_kexec_32.c
+++ b/arch/x86/kernel/machine_kexec_32.c
@@ -199,7 +199,8 @@ void machine_kexec(struct kimage *image)
 		 * one form or other. kexec jump path also need
 		 * one.
 		 */
-		disable_IO_APIC();
+		clear_IO_APIC();
+		restore_boot_irq_mode();
 #endif
 	}
 
diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
index 1f790cf9d38f..2ab14b9c1a89 100644
--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c
@@ -297,7 +297,8 @@ void machine_kexec(struct kimage *image)
 		 * one form or other. kexec jump path also need
 		 * one.
 		 */
-		disable_IO_APIC();
+		clear_IO_APIC();
+		restore_boot_irq_mode();
 #endif
 	}
 
diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c
index 2126b9d27c34..725624b6c0c0 100644
--- a/arch/x86/kernel/reboot.c
+++ b/arch/x86/kernel/reboot.c
@@ -666,7 +666,7 @@ void native_machine_shutdown(void)
 	 * Even without the erratum, it still makes sense to quiet IO APIC
 	 * before disabling Local APIC.
 	 */
-	disable_IO_APIC();
+	clear_IO_APIC();
 #endif
 
 #ifdef CONFIG_SMP
@@ -680,6 +680,7 @@ void native_machine_shutdown(void)
 #endif
 
 	lapic_shutdown();
+	restore_boot_irq_mode();
 
 #ifdef CONFIG_HPET_TIMER
 	hpet_disable();
-- 
2.13.6

[PATCH v4 3/5] x86/apic: Remove useless disable_IO_APIC

[Baoquan He]

No one uses it anymore.

Signed-off-by: Baoquan He <bhe@redhat.com>
---
 arch/x86/include/asm/io_apic.h     |  1 -
 arch/x86/kernel/apic/io_apic.c     | 13 -------------
 arch/x86/kernel/machine_kexec_32.c |  5 ++---
 arch/x86/kernel/machine_kexec_64.c |  5 ++---
 4 files changed, 4 insertions(+), 20 deletions(-)

diff --git a/arch/x86/include/asm/io_apic.h b/arch/x86/include/asm/io_apic.h
index 0fa95bfacb39..5e389145d808 100644
--- a/arch/x86/include/asm/io_apic.h
+++ b/arch/x86/include/asm/io_apic.h
@@ -192,7 +192,6 @@ static inline unsigned int io_apic_read(unsigned int apic, unsigned int reg)
 
 extern void setup_IO_APIC(void);
 extern void enable_IO_APIC(void);
-extern void disable_IO_APIC(void);
 extern void clear_IO_APIC(void);
 extern void restore_boot_irq_mode(void);
 extern int IO_APIC_get_PCI_irq_vector(int bus, int devfn, int pin);
diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index 2d7cd2db77f5..9d86b10c2121 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -1438,19 +1438,6 @@ void native_disable_io_apic(void)
 		disconnect_bsp_APIC(ioapic_i8259.pin != -1);
 }
 
-/*
- * Not an __init, needed by the reboot code
- */
-void disable_IO_APIC(void)
-{
-	/*
-	 * Clear the IO-APIC before rebooting:
-	 */
-	clear_IO_APIC();
-
-	restore_boot_irq_mode();
-}
-
 void restore_boot_irq_mode(void)
 {
 	if (!nr_legacy_irqs())
diff --git a/arch/x86/kernel/machine_kexec_32.c b/arch/x86/kernel/machine_kexec_32.c
index 4cd79d88a4ac..60cdec6628b0 100644
--- a/arch/x86/kernel/machine_kexec_32.c
+++ b/arch/x86/kernel/machine_kexec_32.c
@@ -195,9 +195,8 @@ void machine_kexec(struct kimage *image)
 		/*
 		 * We need to put APICs in legacy mode so that we can
 		 * get timer interrupts in second kernel. kexec/kdump
-		 * paths already have calls to disable_IO_APIC() in
-		 * one form or other. kexec jump path also need
-		 * one.
+		 * paths already have calls to restore_boot_irq_mode()
+		 * in one form or other. kexec jump path also need one.
 		 */
 		clear_IO_APIC();
 		restore_boot_irq_mode();
diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
index 2ab14b9c1a89..5ffbc55ea80f 100644
--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c
@@ -293,9 +293,8 @@ void machine_kexec(struct kimage *image)
 		/*
 		 * We need to put APICs in legacy mode so that we can
 		 * get timer interrupts in second kernel. kexec/kdump
-		 * paths already have calls to disable_IO_APIC() in
-		 * one form or other. kexec jump path also need
-		 * one.
+		 * paths already have calls to restore_boot_irq_mode()
+		 * in one form or other. kexec jump path also need one.
 		 */
 		clear_IO_APIC();
 		restore_boot_irq_mode();
-- 
2.13.6

[PATCH v4 4/5] x86/apic: Rename variable/function related to x86_io_apic_ops

[Baoquan He]

The names of x86_io_apic_ops and its two member variables, are
misleading. The .read member is to read IO_APIC reg, while .disable
which hook native_disable_io_apic/irq_remapping_disable_io_apic
is actually used to restore boot irq mode, not disable IO_APIC.

So rename x86_io_apic_ops to x86_apic_ops since it doesn't only
handle IO_APIC, also LAPIC.

And also rename its member variables and the related hooks.

Signed-off-by: Baoquan He <bhe@redhat.com>
---
 arch/x86/include/asm/io_apic.h  | 6 +++---
 arch/x86/include/asm/x86_init.h | 8 ++++----
 arch/x86/kernel/apic/io_apic.c  | 4 ++--
 arch/x86/kernel/x86_init.c      | 6 +++---
 arch/x86/xen/apic.c             | 2 +-
 drivers/iommu/irq_remapping.c   | 4 ++--
 6 files changed, 15 insertions(+), 15 deletions(-)

diff --git a/arch/x86/include/asm/io_apic.h b/arch/x86/include/asm/io_apic.h
index 5e389145d808..06fec4426458 100644
--- a/arch/x86/include/asm/io_apic.h
+++ b/arch/x86/include/asm/io_apic.h
@@ -183,11 +183,11 @@ extern void disable_ioapic_support(void);
 
 extern void __init io_apic_init_mappings(void);
 extern unsigned int native_io_apic_read(unsigned int apic, unsigned int reg);
-extern void native_disable_io_apic(void);
+extern void native_restore_boot_irq_mode(void);
 
 static inline unsigned int io_apic_read(unsigned int apic, unsigned int reg)
 {
-	return x86_io_apic_ops.read(apic, reg);
+	return x86_apic_ops.io_apic_read(apic, reg);
 }
 
 extern void setup_IO_APIC(void);
@@ -229,7 +229,7 @@ static inline void mp_save_irq(struct mpc_intsrc *m) { }
 static inline void disable_ioapic_support(void) { }
 static inline void io_apic_init_mappings(void) { }
 #define native_io_apic_read		NULL
-#define native_disable_io_apic		NULL
+#define native_restore_boot_irq_mode	NULL
 
 static inline void setup_IO_APIC(void) { }
 static inline void enable_IO_APIC(void) { }
diff --git a/arch/x86/include/asm/x86_init.h b/arch/x86/include/asm/x86_init.h
index fc2f082ac635..88306054bd98 100644
--- a/arch/x86/include/asm/x86_init.h
+++ b/arch/x86/include/asm/x86_init.h
@@ -274,16 +274,16 @@ struct x86_msi_ops {
 	void (*restore_msi_irqs)(struct pci_dev *dev);
 };
 
-struct x86_io_apic_ops {
-	unsigned int	(*read)   (unsigned int apic, unsigned int reg);
-	void		(*disable)(void);
+struct x86_apic_ops {
+	unsigned int	(*io_apic_read)   (unsigned int apic, unsigned int reg);
+	void		(*restore)(void);
 };
 
 extern struct x86_init_ops x86_init;
 extern struct x86_cpuinit_ops x86_cpuinit;
 extern struct x86_platform_ops x86_platform;
 extern struct x86_msi_ops x86_msi;
-extern struct x86_io_apic_ops x86_io_apic_ops;
+extern struct x86_apic_ops x86_apic_ops;
 
 extern void x86_early_init_platform_quirks(void);
 extern void x86_init_noop(void);
diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index 9d86b10c2121..68129f11e7db 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -1410,7 +1410,7 @@ void __init enable_IO_APIC(void)
 	clear_IO_APIC();
 }
 
-void native_disable_io_apic(void)
+void native_restore_boot_irq_mode(void)
 {
 	/*
 	 * If the i8259 is routed through an IOAPIC
@@ -1443,7 +1443,7 @@ void restore_boot_irq_mode(void)
 	if (!nr_legacy_irqs())
 		return;
 
-	x86_io_apic_ops.disable();
+	x86_apic_ops.restore();
 }
 
 #ifdef CONFIG_X86_32
diff --git a/arch/x86/kernel/x86_init.c b/arch/x86/kernel/x86_init.c
index 1151ccd72ce9..2bccd03bd654 100644
--- a/arch/x86/kernel/x86_init.c
+++ b/arch/x86/kernel/x86_init.c
@@ -146,7 +146,7 @@ void arch_restore_msi_irqs(struct pci_dev *dev)
 }
 #endif
 
-struct x86_io_apic_ops x86_io_apic_ops __ro_after_init = {
-	.read			= native_io_apic_read,
-	.disable		= native_disable_io_apic,
+struct x86_apic_ops x86_apic_ops __ro_after_init = {
+	.io_apic_read	= native_io_apic_read,
+	.restore	= native_restore_boot_irq_mode,
 };
diff --git a/arch/x86/xen/apic.c b/arch/x86/xen/apic.c
index de58533d3664..2163888497d3 100644
--- a/arch/x86/xen/apic.c
+++ b/arch/x86/xen/apic.c
@@ -215,7 +215,7 @@ static void __init xen_apic_check(void)
 }
 void __init xen_init_apic(void)
 {
-	x86_io_apic_ops.read = xen_io_apic_read;
+	x86_apic_ops.io_apic_read = xen_io_apic_read;
 	/* On PV guests the APIC CPUID bit is disabled so none of the
 	 * routines end up executing. */
 	if (!xen_initial_domain())
diff --git a/drivers/iommu/irq_remapping.c b/drivers/iommu/irq_remapping.c
index 49721b4e1975..496deee3ae3a 100644
--- a/drivers/iommu/irq_remapping.c
+++ b/drivers/iommu/irq_remapping.c
@@ -27,7 +27,7 @@ int disable_irq_post = 0;
 static int disable_irq_remap;
 static struct irq_remap_ops *remap_ops;
 
-static void irq_remapping_disable_io_apic(void)
+static void irq_remapping_restore_boot_irq_mode(void)
 {
 	/*
 	 * With interrupt-remapping, for now we will use virtual wire A
@@ -42,7 +42,7 @@ static void irq_remapping_disable_io_apic(void)
 
 static void __init irq_remapping_modify_x86_ops(void)
 {
-	x86_io_apic_ops.disable		= irq_remapping_disable_io_apic;
+	x86_apic_ops.restore = irq_remapping_restore_boot_irq_mode;
 }
 
 static __init int setup_nointremap(char *str)
-- 
2.13.6

Re: [PATCH v4 4/5] x86/apic: Rename variable/function related to x86_io_apic_ops

[kbuild test robot]

[-- Attachment #1: Type: text/plain, Size: 2209 bytes --]

Hi Baoquan,

I love your patch! Yet something to improve:

[auto build test ERROR on tip/auto-latest]
[also build test ERROR on v4.16-rc1 next-20180215]
[cannot apply to tip/x86/core]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Baoquan-He/x86-apic-Fix-restoring-boot-irq-mode-in-reboot-and-kexec-kdump/20180216-121305
config: i386-randconfig-x070-201806 (attached as .config)
compiler: gcc-7 (Debian 7.3.0-1) 7.3.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

All errors (new ones prefixed by >>):

   arch/x86/kernel/reboot.c: In function 'native_machine_shutdown':
>> arch/x86/kernel/reboot.c:683:2: error: implicit declaration of function 'restore_boot_irq_mode'; did you mean 'native_restore_boot_irq_mode'? [-Werror=implicit-function-declaration]
     restore_boot_irq_mode();
     ^~~~~~~~~~~~~~~~~~~~~
     native_restore_boot_irq_mode
   cc1: some warnings being treated as errors
--
   arch/x86/kernel/crash.c: In function 'native_machine_crash_shutdown':
>> arch/x86/kernel/crash.c:205:2: error: implicit declaration of function 'restore_boot_irq_mode'; did you mean 'native_restore_boot_irq_mode'? [-Werror=implicit-function-declaration]
     restore_boot_irq_mode();
     ^~~~~~~~~~~~~~~~~~~~~
     native_restore_boot_irq_mode
   cc1: some warnings being treated as errors

vim +683 arch/x86/kernel/reboot.c

^1da177e arch/i386/kernel/reboot.c Linus Torvalds 2005-04-16  681  
^1da177e arch/i386/kernel/reboot.c Linus Torvalds 2005-04-16  682  	lapic_shutdown();
4bfde7d3 arch/x86/kernel/reboot.c  Baoquan He     2018-02-13 @683  	restore_boot_irq_mode();
^1da177e arch/i386/kernel/reboot.c Linus Torvalds 2005-04-16  684  

:::::: The code at line 683 was first introduced by commit
:::::: 4bfde7d3821a914fb062d96979559723e5871c3d x86/apic: Fix restoring boot irq mode in reboot and kexec/kdump

:::::: TO: Baoquan He <bhe@redhat.com>
:::::: CC: 0day robot <fengguang.wu@intel.com>

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

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[PATCH v4 5/5] x86/apic: Set up through-local-APIC on boot CPU if 'noapic' specified

[Baoquan He]

Currently kdump kernel becomes very slow if 'noapic' is specified.
Normal kernel won't.

Kernel parameter 'noapic' is used to disable IO-APIC in system for
testing or special purpose. Here the root cause is that in kdump
kernel LAPIC is disabled since commit 522e664644
("x86/apic: Disable I/O APIC before shutdown of the local APIC").
In this case We need set up through-local-APIC on boot CPU in
setup_local_APIC().

While In normal kernel the legacy irq mode is enabled in BIOS. If
it is virtual wire mode, the local-APIC has been enabled and set as
through-local-APIC.

Though we fix the regression introduced by criminal commit 522e664644,
for safety and clarity, better set up through-local-APIC explicitly,
but not rely on the default boot irq mode.

Do it now.

Signed-off-by: Baoquan He <bhe@redhat.com>
---
 arch/x86/kernel/apic/apic.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index 25ddf02598d2..3fc259b4dd2d 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -1570,7 +1570,7 @@ void setup_local_APIC(void)
 	 * TODO: set up through-local-APIC from through-I/O-APIC? --macro
 	 */
 	value = apic_read(APIC_LVT0) & APIC_LVT_MASKED;
-	if (!cpu && (pic_mode || !value)) {
+	if (!cpu && (pic_mode || !value || skip_ioapic_setup)) {
 		value = APIC_DM_EXTINT;
 		apic_printk(APIC_VERBOSE, "enabled ExtINT on CPU#%d\n", cpu);
 	} else {
-- 
2.13.6