[PATCH v5 0/2] Improve interrupt handling during machine kexec

[PATCH v5 0/2] Improve interrupt handling during machine kexec

[Eliav Farber]

This patch series focuses on improving the machine_kexec_mask_interrupts()
function by consolidating its implementation and optimizing its behavior to
avoid redundant interrupt masking.

Patch Summary:
[PATCH v5 1/2] Move machine_kexec_mask_interrupts() to kernel/irq/kexec.c,
               removing duplicate architecture-specific implementations.
[PATCH v5 2/2] Refine machine_kexec_mask_interrupts() to avoid re-masking
               already-masked interrupts, resolving specific warnings
               triggered in GPIO IRQ flows.

Changes between v4 and v5:
 - The function machine_kexec_mask_interrupts() has been moved
   from kernel/kexec_core.c to a new file kernel/irq/kexec.c.
 - A new configuration option, GENERIC_IRQ_KEXEC_CLEAR_VM_FORWARD, has been
   added.
 - The parameters for the machine_kexec_mask_interrupts() function have
   been defined in reverse Christmas Tree style.
 - The comment explaining the call to irq_set_irqchip_state() has been
   improved for clarity.
 - The phrase 'This patch' has been removed from the commit message.
 
Changes between v3 and v4:
 - Add missing <linux/irqdesc.h> and <linux/irq.h> includes.

Eliav Farber (2):
  kexec: Consolidate machine_kexec_mask_interrupts() implementation
  kexec: Prevent redundant IRQ masking by checking state before shutdown

 arch/arm/kernel/machine_kexec.c   | 23 --------------------
 arch/arm64/Kconfig                |  1 +
 arch/arm64/kernel/machine_kexec.c | 31 --------------------------
 arch/powerpc/include/asm/kexec.h  |  1 -
 arch/powerpc/kexec/core.c         | 22 -------------------
 arch/powerpc/kexec/core_32.c      |  1 +
 arch/riscv/kernel/machine_kexec.c | 23 --------------------
 include/linux/irq.h               |  3 +++
 kernel/irq/Kconfig                |  9 ++++++++
 kernel/irq/Makefile               |  2 +-
 kernel/irq/kexec.c                | 36 +++++++++++++++++++++++++++++++
 11 files changed, 51 insertions(+), 101 deletions(-)
 create mode 100644 kernel/irq/kexec.c

-- 
2.40.1

[PATCH v5 1/2] kexec: Consolidate machine_kexec_mask_interrupts() implementation

[Eliav Farber]

Consolidate the machine_kexec_mask_interrupts implementation into a common
function located in a new file: kernel/irq/kexec.c. This removes duplicate
implementations from architecture-specific files in arch/arm, arch/arm64,
arch/powerpc, and arch/riscv, reducing code duplication and improving
maintainability.

The new implementation retains architecture-specific behavior for
CONFIG_GENERIC_IRQ_KEXEC_CLEAR_VM_FORWARD, which was previously implemented
for ARM64. When enabled (currently for ARM64), it clears the active state
of interrupts forwarded to virtual machines (VMs) before handling other
interrupt masking operations.

Signed-off-by: Eliav Farber <farbere@amazon.com>
---
V4 -> V5:
 - The function machine_kexec_mask_interrupts() has been moved
   from kernel/kexec_core.c to a new file kernel/irq/kexec.c.
 - A new configuration option, GENERIC_IRQ_KEXEC_CLEAR_VM_FORWARD, has been
   added.
 - The parameters for the machine_kexec_mask_interrupts() function have
   been defined in reverse Christmas Tree style.
 - The comment explaining the call to irq_set_irqchip_state() has been
   improved for clarity.

 arch/arm/kernel/machine_kexec.c   | 23 ------------------
 arch/arm64/Kconfig                |  1 +
 arch/arm64/kernel/machine_kexec.c | 31 ------------------------
 arch/powerpc/include/asm/kexec.h  |  1 -
 arch/powerpc/kexec/core.c         | 22 -----------------
 arch/powerpc/kexec/core_32.c      |  1 +
 arch/riscv/kernel/machine_kexec.c | 23 ------------------
 include/linux/irq.h               |  3 +++
 kernel/irq/Kconfig                |  9 +++++++
 kernel/irq/Makefile               |  2 +-
 kernel/irq/kexec.c                | 40 +++++++++++++++++++++++++++++++
 11 files changed, 55 insertions(+), 101 deletions(-)
 create mode 100644 kernel/irq/kexec.c

diff --git a/arch/arm/kernel/machine_kexec.c b/arch/arm/kernel/machine_kexec.c
index 80ceb5bd2680..dd430477e7c1 100644
--- a/arch/arm/kernel/machine_kexec.c
+++ b/arch/arm/kernel/machine_kexec.c
@@ -127,29 +127,6 @@ void crash_smp_send_stop(void)
 	cpus_stopped = 1;
 }
 
-static void machine_kexec_mask_interrupts(void)
-{
-	unsigned int i;
-	struct irq_desc *desc;
-
-	for_each_irq_desc(i, desc) {
-		struct irq_chip *chip;
-
-		chip = irq_desc_get_chip(desc);
-		if (!chip)
-			continue;
-
-		if (chip->irq_eoi && irqd_irq_inprogress(&desc->irq_data))
-			chip->irq_eoi(&desc->irq_data);
-
-		if (chip->irq_mask)
-			chip->irq_mask(&desc->irq_data);
-
-		if (chip->irq_disable && !irqd_irq_disabled(&desc->irq_data))
-			chip->irq_disable(&desc->irq_data);
-	}
-}
-
 void machine_crash_shutdown(struct pt_regs *regs)
 {
 	local_irq_disable();
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index d743737bf9ce..359b9dcb35b9 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -150,6 +150,7 @@ config ARM64
 	select GENERIC_IDLE_POLL_SETUP
 	select GENERIC_IOREMAP
 	select GENERIC_IRQ_IPI
+	select GENERIC_IRQ_KEXEC_CLEAR_VM_FORWARD
 	select GENERIC_IRQ_PROBE
 	select GENERIC_IRQ_SHOW
 	select GENERIC_IRQ_SHOW_LEVEL
diff --git a/arch/arm64/kernel/machine_kexec.c b/arch/arm64/kernel/machine_kexec.c
index 82e2203d86a3..6f121a0164a4 100644
--- a/arch/arm64/kernel/machine_kexec.c
+++ b/arch/arm64/kernel/machine_kexec.c
@@ -207,37 +207,6 @@ void machine_kexec(struct kimage *kimage)
 	BUG(); /* Should never get here. */
 }
 
-static void machine_kexec_mask_interrupts(void)
-{
-	unsigned int i;
-	struct irq_desc *desc;
-
-	for_each_irq_desc(i, desc) {
-		struct irq_chip *chip;
-		int ret;
-
-		chip = irq_desc_get_chip(desc);
-		if (!chip)
-			continue;
-
-		/*
-		 * First try to remove the active state. If this
-		 * fails, try to EOI the interrupt.
-		 */
-		ret = irq_set_irqchip_state(i, IRQCHIP_STATE_ACTIVE, false);
-
-		if (ret && irqd_irq_inprogress(&desc->irq_data) &&
-		    chip->irq_eoi)
-			chip->irq_eoi(&desc->irq_data);
-
-		if (chip->irq_mask)
-			chip->irq_mask(&desc->irq_data);
-
-		if (chip->irq_disable && !irqd_irq_disabled(&desc->irq_data))
-			chip->irq_disable(&desc->irq_data);
-	}
-}
-
 /**
  * machine_crash_shutdown - shutdown non-crashing cpus and save registers
  */
diff --git a/arch/powerpc/include/asm/kexec.h b/arch/powerpc/include/asm/kexec.h
index 270ee93a0f7d..601e569303e1 100644
--- a/arch/powerpc/include/asm/kexec.h
+++ b/arch/powerpc/include/asm/kexec.h
@@ -61,7 +61,6 @@ struct pt_regs;
 extern void kexec_smp_wait(void);	/* get and clear naca physid, wait for
 					  master to copy new code to 0 */
 extern void default_machine_kexec(struct kimage *image);
-extern void machine_kexec_mask_interrupts(void);
 
 void relocate_new_kernel(unsigned long indirection_page, unsigned long reboot_code_buffer,
 			 unsigned long start_address) __noreturn;
diff --git a/arch/powerpc/kexec/core.c b/arch/powerpc/kexec/core.c
index b8333a49ea5d..58a930a47422 100644
--- a/arch/powerpc/kexec/core.c
+++ b/arch/powerpc/kexec/core.c
@@ -22,28 +22,6 @@
 #include <asm/setup.h>
 #include <asm/firmware.h>
 
-void machine_kexec_mask_interrupts(void) {
-	unsigned int i;
-	struct irq_desc *desc;
-
-	for_each_irq_desc(i, desc) {
-		struct irq_chip *chip;
-
-		chip = irq_desc_get_chip(desc);
-		if (!chip)
-			continue;
-
-		if (chip->irq_eoi && irqd_irq_inprogress(&desc->irq_data))
-			chip->irq_eoi(&desc->irq_data);
-
-		if (chip->irq_mask)
-			chip->irq_mask(&desc->irq_data);
-
-		if (chip->irq_disable && !irqd_irq_disabled(&desc->irq_data))
-			chip->irq_disable(&desc->irq_data);
-	}
-}
-
 #ifdef CONFIG_CRASH_DUMP
 void machine_crash_shutdown(struct pt_regs *regs)
 {
diff --git a/arch/powerpc/kexec/core_32.c b/arch/powerpc/kexec/core_32.c
index c95f96850c9e..deb28eb44f30 100644
--- a/arch/powerpc/kexec/core_32.c
+++ b/arch/powerpc/kexec/core_32.c
@@ -7,6 +7,7 @@
  * Copyright (C) 2005 IBM Corporation.
  */
 
+#include <linux/irq.h>
 #include <linux/kexec.h>
 #include <linux/mm.h>
 #include <linux/string.h>
diff --git a/arch/riscv/kernel/machine_kexec.c b/arch/riscv/kernel/machine_kexec.c
index 3c830a6f7ef4..2306ce3e5f22 100644
--- a/arch/riscv/kernel/machine_kexec.c
+++ b/arch/riscv/kernel/machine_kexec.c
@@ -114,29 +114,6 @@ void machine_shutdown(void)
 #endif
 }
 
-static void machine_kexec_mask_interrupts(void)
-{
-	unsigned int i;
-	struct irq_desc *desc;
-
-	for_each_irq_desc(i, desc) {
-		struct irq_chip *chip;
-
-		chip = irq_desc_get_chip(desc);
-		if (!chip)
-			continue;
-
-		if (chip->irq_eoi && irqd_irq_inprogress(&desc->irq_data))
-			chip->irq_eoi(&desc->irq_data);
-
-		if (chip->irq_mask)
-			chip->irq_mask(&desc->irq_data);
-
-		if (chip->irq_disable && !irqd_irq_disabled(&desc->irq_data))
-			chip->irq_disable(&desc->irq_data);
-	}
-}
-
 /*
  * machine_crash_shutdown - Prepare to kexec after a kernel crash
  *
diff --git a/include/linux/irq.h b/include/linux/irq.h
index fa711f80957b..25f51bf3c351 100644
--- a/include/linux/irq.h
+++ b/include/linux/irq.h
@@ -694,6 +694,9 @@ extern int irq_chip_request_resources_parent(struct irq_data *data);
 extern void irq_chip_release_resources_parent(struct irq_data *data);
 #endif
 
+/* Disable or mask interrupts during a kernel kexec */
+extern void machine_kexec_mask_interrupts(void);
+
 /* Handling of unhandled and spurious interrupts: */
 extern void note_interrupt(struct irq_desc *desc, irqreturn_t action_ret);
 
diff --git a/kernel/irq/Kconfig b/kernel/irq/Kconfig
index 529adb1f5859..5967accb8e87 100644
--- a/kernel/irq/Kconfig
+++ b/kernel/irq/Kconfig
@@ -154,3 +154,12 @@ config DEPRECATED_IRQ_CPU_ONOFFLINE
 	bool
 	depends on CAVIUM_OCTEON_SOC
 	default CAVIUM_OCTEON_SOC
+
+config GENERIC_IRQ_KEXEC_CLEAR_VM_FORWARD
+	bool "Clear forwarded VM interrupts during kexec"
+	default n
+	help
+	  When enabled, this option allows the kernel to clear the active state
+	  of interrupts that are forwarded to virtual machines (VMs) during a
+	  machine kexec. For interrupts that are not forwarded, if supported,
+	  the kernel will attempt to trigger an End of Interrupt (EOI).
diff --git a/kernel/irq/Makefile b/kernel/irq/Makefile
index f19d3080bf11..c0f44c06d69d 100644
--- a/kernel/irq/Makefile
+++ b/kernel/irq/Makefile
@@ -1,6 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0
 
-obj-y := irqdesc.o handle.o manage.o spurious.o resend.o chip.o dummychip.o devres.o
+obj-y := irqdesc.o handle.o manage.o spurious.o resend.o chip.o dummychip.o devres.o kexec.o
 obj-$(CONFIG_IRQ_TIMINGS) += timings.o
 ifeq ($(CONFIG_TEST_IRQ_TIMINGS),y)
 	CFLAGS_timings.o += -DDEBUG
diff --git a/kernel/irq/kexec.c b/kernel/irq/kexec.c
new file mode 100644
index 000000000000..0f9548c1708d
--- /dev/null
+++ b/kernel/irq/kexec.c
@@ -0,0 +1,40 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/irqdesc.h>
+#include <linux/irqnr.h>
+
+#include "internals.h"
+
+void machine_kexec_mask_interrupts(void)
+{
+	struct irq_desc *desc;
+	unsigned int i;
+
+	for_each_irq_desc(i, desc) {
+		struct irq_chip *chip;
+		int check_eoi = 1;
+
+		chip = irq_desc_get_chip(desc);
+		if (!chip)
+			continue;
+
+		if (IS_ENABLED(CONFIG_GENERIC_IRQ_KEXEC_CLEAR_VM_FORWARD)) {
+			/*
+			 * First try to remove the active state from an interrupt which is forwarded
+			 * to a VM. If the interrupt is not forwarded, try to EOI the interrupt.
+			 */
+			check_eoi = irq_set_irqchip_state(i, IRQCHIP_STATE_ACTIVE, false);
+		}
+
+		if (check_eoi && chip->irq_eoi && irqd_irq_inprogress(&desc->irq_data))
+			chip->irq_eoi(&desc->irq_data);
+
+		if (chip->irq_mask)
+			chip->irq_mask(&desc->irq_data);
+
+		if (chip->irq_disable && !irqd_irq_disabled(&desc->irq_data))
+			chip->irq_disable(&desc->irq_data);
+	}
+}
-- 
2.40.1

[PATCH v5 2/2] kexec: Prevent redundant IRQ masking by checking state before shutdown

[Eliav Farber]

During machine kexec, the function machine_kexec_mask_interrupts() is
responsible for disabling or masking all interrupts. While the irq_disable
hook ensures that an already-disabled IRQ is not disabled again, the
current implementation unconditionally invokes the irq_mask() function for
every interrupt descriptor, even when the interrupt is already masked.

A specific issue was observed in the crash kernel flow after unbinding a
device (prior to kexec) that used a GPIO as an IRQ source. The warning was
triggered by the gpiochip_disable_irq() function, which attempted to clear
the FLAG_IRQ_IS_ENABLED flag when FLAG_USED_AS_IRQ was not set:

```
void gpiochip_disable_irq(struct gpio_chip *gc, unsigned int offset)
{
	struct gpio_desc *desc = gpiochip_get_desc(gc, offset);

	if (!IS_ERR(desc) &&
	    !WARN_ON(!test_bit(FLAG_USED_AS_IRQ, &desc->flags)))
		clear_bit(FLAG_IRQ_IS_ENABLED, &desc->flags);
}
```

This issue surfaced after commit a8173820f441 ("gpio: gpiolib: Allow GPIO
IRQs to lazy disable") introduced lazy disablement for GPIO IRQs. It
replaced disable/enable hooks with mask/unmask hooks. Unlike the disable
hook, the mask hook doesn't handle already-masked IRQs.

When a GPIO-IRQ driver is unbound, the IRQ is released, triggering
__irq_disable() and irq_state_set_masked(). A subsequent call to
machine_kexec_mask_interrupts() re-invokes chip->irq_mask(). This results
in a call chain, including gpiochip_irq_mask() and gpiochip_disable_irq().
Since FLAG_USED_AS_IRQ was cleared earlier, a warning occurs.

Replace calls to irq_mask() and irq_disable() hooks with a simplified call
to irq_shutdown(), and check if the interrupt is started (irqd_is_started)
before calling the shutdown.

Signed-off-by: Eliav Farber <farbere@amazon.com>
---
V4 -> V5:
 - The phrase 'This patch' has been removed from the commit message.

 kernel/irq/kexec.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/kernel/irq/kexec.c b/kernel/irq/kexec.c
index 0f9548c1708d..1a3deffe6b5b 100644
--- a/kernel/irq/kexec.c
+++ b/kernel/irq/kexec.c
@@ -17,7 +17,7 @@ void machine_kexec_mask_interrupts(void)
 		int check_eoi = 1;
 
 		chip = irq_desc_get_chip(desc);
-		if (!chip)
+		if (!chip || !irqd_is_started(&desc->irq_data))
 			continue;
 
 		if (IS_ENABLED(CONFIG_GENERIC_IRQ_KEXEC_CLEAR_VM_FORWARD)) {
@@ -31,10 +31,6 @@ void machine_kexec_mask_interrupts(void)
 		if (check_eoi && chip->irq_eoi && irqd_irq_inprogress(&desc->irq_data))
 			chip->irq_eoi(&desc->irq_data);
 
-		if (chip->irq_mask)
-			chip->irq_mask(&desc->irq_data);
-
-		if (chip->irq_disable && !irqd_irq_disabled(&desc->irq_data))
-			chip->irq_disable(&desc->irq_data);
+		irq_shutdown(desc);
 	}
 }
-- 
2.40.1

Re: [PATCH v5 1/2] kexec: Consolidate machine_kexec_mask_interrupts() implementation

[Thomas Gleixner]

On Sat, Nov 30 2024 at 20:11, Eliav Farber wrote:
> +
> +config GENERIC_IRQ_KEXEC_CLEAR_VM_FORWARD
> +	bool "Clear forwarded VM interrupts during kexec"

This should not be user selectable. Just keep it as:

config GENERIC_IRQ_KEXEC_CLEAR_VM_FORWARD
	bool

which defaults to 'n'. Just add a comment what this is about like it's
done with the other options in that file which are only selectable.

Thanks,

        tglx

Re: [PATCH v5 1/2] kexec: Consolidate machine_kexec_mask_interrupts() implementation

[Jiri Slaby]

On 30. 11. 24, 21:11, Eliav Farber wrote:
> Consolidate the machine_kexec_mask_interrupts implementation into a common
> function located in a new file: kernel/irq/kexec.c. This removes duplicate
> implementations from architecture-specific files in arch/arm, arch/arm64,
> arch/powerpc, and arch/riscv, reducing code duplication and improving
> maintainability.
> 
> The new implementation retains architecture-specific behavior for
> CONFIG_GENERIC_IRQ_KEXEC_CLEAR_VM_FORWARD, which was previously implemented
> for ARM64. When enabled (currently for ARM64), it clears the active state
> of interrupts forwarded to virtual machines (VMs) before handling other
> interrupt masking operations.
...
> --- a/kernel/irq/Kconfig
> +++ b/kernel/irq/Kconfig
> @@ -154,3 +154,12 @@ config DEPRECATED_IRQ_CPU_ONOFFLINE
>   	bool
>   	depends on CAVIUM_OCTEON_SOC
>   	default CAVIUM_OCTEON_SOC
> +
> +config GENERIC_IRQ_KEXEC_CLEAR_VM_FORWARD
> +	bool "Clear forwarded VM interrupts during kexec"
> +	default n
> +	help
> +	  When enabled, this option allows the kernel to clear the active state
> +	  of interrupts that are forwarded to virtual machines (VMs) during a
> +	  machine kexec. For interrupts that are not forwarded, if supported,
> +	  the kernel will attempt to trigger an End of Interrupt (EOI).

This caught my attention. It looks like you want to allow people 
toggling it? I believe only arch code should turn it on as you do by 
"select", not users.

thanks,
-- 
js
suse labs