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Subject[PATCH v2 1/2] x86/apic/kexec: Enable legacy irq mode before jump to kexec/kdump kernel
Date
On kvm guest, kernel always prints warning during kdump kernel boots as
below.

[ 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

The root cause is the legacy irq mode is disabled before jump to kexec/kdump
kernel since commit 522e66464467 ("x86/apic: Disable I/O APIC before shutdown
of the local APIC"). In that commit, lapic_shutdown() calling was moved after
disable_IO_APIC(). In fact in disable_IO_APIC(), it not only calls
clear_IO_APIC() to disable IO-APIC, and also sets LAPIC and IO-APIC to make
system be PIC or Virtual wire mode. Hence local APIC is disabled completely
by the calling of lapic_shutdown().

Later in kdump kernel, when calling setup_local_APIC(), the
'do { xxx } while (queued && max_loops > 0)' loop does not function well any
more if pending irq exists in APIC IRR since LAPIC is disabled. The do while
loop will terminate finally when max_loops overflows by subtraction. Then,
next WARN_ON(max_loops <= 0) is triggered.

In normal kernel it defaults to be PIC mode or Virtual Wire mode which is
done by BIOS. But kexec/kdump kernel won't go through BIOS, we need set
system as PIC or Virtual Wire mode before jump to kdump kernel code directly.
With this the pending irq can be handled correclty before APIC mode enabling.

So take clear_IO_APIC out of disable_IO_APIC, and rename disable_IO_APIC
as switch_to_legacy_irq_mode. Then only call clear_IO_APIC when IO-APIC
need be disabled. And call switch_to_legacy_irq_mode before kexec/kdump
jumping.

Signed-off-by: Baoquan He <bhe@redhat.com>
---
arch/x86/include/asm/io_apic.h | 3 ++-
arch/x86/kernel/apic/io_apic.c | 12 ++++--------
arch/x86/kernel/crash.c | 2 +-
arch/x86/kernel/machine_kexec_32.c | 15 +++++----------
arch/x86/kernel/machine_kexec_64.c | 15 +++++----------
arch/x86/kernel/reboot.c | 2 +-
6 files changed, 18 insertions(+), 31 deletions(-)

diff --git a/arch/x86/include/asm/io_apic.h b/arch/x86/include/asm/io_apic.h
index a8834dd546cd..e38ad3863a2c 100644
--- a/arch/x86/include/asm/io_apic.h
+++ b/arch/x86/include/asm/io_apic.h
@@ -192,7 +192,8 @@ 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 switch_to_legacy_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 8a7963421460..a47aa915d18c 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;

@@ -1439,15 +1439,11 @@ void native_disable_io_apic(void)
}

/*
- * Not an __init, needed by the reboot code
+ * Not an __init, needed by kexec/kdump code.
+ * For safety IO-APIC and Local APIC need be cleared before this.
*/
-void disable_IO_APIC(void)
+void switch_to_legacy_irq_mode(void)
{
- /*
- * Clear the IO-APIC before rebooting:
- */
- clear_IO_APIC();
-
if (!nr_legacy_irqs())
return;

diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index 10e74d4778a1..318ffeaaf55a 100644
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -199,7 +199,7 @@ 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();
#ifdef CONFIG_HPET_TIMER
diff --git a/arch/x86/kernel/machine_kexec_32.c b/arch/x86/kernel/machine_kexec_32.c
index edfede768688..7ab10d930cc6 100644
--- a/arch/x86/kernel/machine_kexec_32.c
+++ b/arch/x86/kernel/machine_kexec_32.c
@@ -190,18 +190,13 @@ void machine_kexec(struct kimage *image)
local_irq_disable();
hw_breakpoint_disable();

- if (image->preserve_context) {
#ifdef CONFIG_X86_IO_APIC
- /*
- * 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.
- */
- disable_IO_APIC();
+ /*
+ * We need to put APICs in legacy mode so that we can
+ * get timer interrupts in second kernel.
+ */
+ switch_to_legacy_irq_mode();
#endif
- }

control_page = page_address(image->control_code_page);
memcpy(control_page, relocate_kernel, KEXEC_CONTROL_CODE_MAX_SIZE);
diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
index 1f790cf9d38f..b5c0cbed6791 100644
--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c
@@ -288,18 +288,13 @@ void machine_kexec(struct kimage *image)
local_irq_disable();
hw_breakpoint_disable();

- if (image->preserve_context) {
#ifdef CONFIG_X86_IO_APIC
- /*
- * 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.
- */
- disable_IO_APIC();
+ /*
+ * We need to put APICs in legacy mode so that we can
+ * get timer interrupts in second kernel.
+ */
+ switch_to_legacy_irq_mode();
#endif
- }

control_page = page_address(image->control_code_page) + PAGE_SIZE;
memcpy(control_page, relocate_kernel, KEXEC_CONTROL_CODE_MAX_SIZE);
diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c
index 2126b9d27c34..b70cc0f38a29 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
--
2.13.6
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