Re: [RESEND PATCH 2/3] x86/apic/kexec: Enable legacy irq mode before jump to kexec/kdump kernel
From: Dou Liyang
Date: Fri Jan 19 2018 - 01:24:40 EST
Hi Baoquan,
At 01/17/2018 06:08 PM, Baoquan He wrote:
On 01/17/18 at 05:47pm, Dou Liyang wrote:
Hi Baoquan,
At 01/05/2018 12:38 PM, Baoquan He wrote:
In commit
commit 522e66464467 ("x86/apic: Disable I/O APIC before shutdown of the local APIC").
lapic_shutdown() invocation is moved after disable_IO_APIC(). In fact
in disable_IO_APIC(), it not only calls clear_IO_APIC() to disable
IO-APIC, also sets sets LAPIC and IO-APIC to make system be PIC or
Virtual wire mode. While the above commit putting disable_IO_APIC earlier
causes local APIC is completely disabled. So the legacy irq mode is
disabled too before jump to kexec/kdump kernel.
I have a question:
As you said, Due to disable_IO_APIC() is triggered before
lapic_shutdown(), So the interrupt virtual wire mode will be disabled.
but, I found that:
After machine_crash_shutdown() is executed, Linux will call
machine_kexec(), and in machine_kexec(), disable_IO_APIC() will also be
called again, why it can't switch to virtual wire mode successfully? Or
is my understanding wrong?
The disable_IO_APIC() calling has a condition check,
if (image->preserve_context) {
disable_IO_APIC();
}
For preserve_context case, it comes from kernel_kexec(). You can check
it in kexec man page, that is another scenario we use kexec for. But not
kexec and kdump.
Understood!
This patch looks good to me and I also tested it, it's OK.
Thanks,
dou.
+--------------+
| __crash_kexec|
+--------------+
|
| +-------------------------+
+--> | machine_crash_shutdown |
| ++------------------------+
| |
| | +-----------------+
| +> | disable_IO_APIC |
| | +-----------------+
| |
| | +----------------+
| +-^+ lapic_shutdown |
| +----------------+
|
| +-------------------------+
+--> | machine_kexec |
| ++------------------------+
| |
| | +-----------------+
| +> | disable_IO_APIC |
| +-----------------+
|
v
Thanks,
dou.
In normal kernel it defaults to be PIC mode or Virtual Wire mode during
system initialization before APIC mode is enabled and this is done by
BIOS initialization. But kexec/kdump kernel won't go through BIOS, so
we should set system as PIC or Virtual Wire mode before jump to kdump
kernel code directly.
So let's take clear_IO_APIC out from 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@xxxxxxxxxx>
---
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