[PATCH v2 0/3] Do IRQ move cleanup with a timer instead of an IPI

[PATCH v2 0/3] Do IRQ move cleanup with a timer instead of an IPI

[Xin Li]

No point to waste a vector for cleaning up the leftovers of a moved
interrupt. Aside of that this must be the lowest priority of all vectors
which makes FRED systems utilizing vectors 0x10-0x1f more complicated
than necessary.

Schedule a timer instead.


Changes since v1:
* Add a lockdep_assert_held() statement to get rid of a bad comment
  that claims __vector_cleanup() needs to be called with vector_lock
  held. (Peter Zijlstra).


Thomas Gleixner (2):
  x86/vector: Rename send_cleanup_vector() to vector_schedule_cleanup()
  x86/vector: Replace IRQ_MOVE_CLEANUP_VECTOR with a timer callback

Xin Li (1):
  tools: Get rid of IRQ_MOVE_CLEANUP_VECTOR from tools

 arch/x86/include/asm/hw_irq.h                 |   4 +-
 arch/x86/include/asm/idtentry.h               |   1 -
 arch/x86/include/asm/irq_vectors.h            |   7 --
 arch/x86/kernel/apic/vector.c                 | 106 ++++++++++++++----
 arch/x86/kernel/idt.c                         |   1 -
 arch/x86/platform/uv/uv_irq.c                 |   2 +-
 drivers/iommu/amd/iommu.c                     |   2 +-
 drivers/iommu/hyperv-iommu.c                  |   4 +-
 drivers/iommu/intel/irq_remapping.c           |   2 +-
 tools/arch/x86/include/asm/irq_vectors.h      |   7 --
 .../beauty/tracepoints/x86_irq_vectors.sh     |   2 +-
 11 files changed, 90 insertions(+), 48 deletions(-)

-- 
2.34.1

[PATCH v2 1/3] x86/vector: Rename send_cleanup_vector() to vector_schedule_cleanup()

[Xin Li]

From: Thomas Gleixner <tglx@linutronix.de>

Rename send_cleanup_vector() to vector_schedule_cleanup() for the next
patch to replace vector cleanup IPI with a timer callback.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Steve Wahl <steve.wahl@hpe.com>
Signed-off-by: Xin Li <xin3.li@intel.com>
---
 arch/x86/include/asm/hw_irq.h       | 4 ++--
 arch/x86/kernel/apic/vector.c       | 8 ++++----
 arch/x86/platform/uv/uv_irq.c       | 2 +-
 drivers/iommu/amd/iommu.c           | 2 +-
 drivers/iommu/hyperv-iommu.c        | 4 ++--
 drivers/iommu/intel/irq_remapping.c | 2 +-
 6 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/arch/x86/include/asm/hw_irq.h b/arch/x86/include/asm/hw_irq.h
index d465ece58151..551829884734 100644
--- a/arch/x86/include/asm/hw_irq.h
+++ b/arch/x86/include/asm/hw_irq.h
@@ -97,10 +97,10 @@ extern struct irq_cfg *irqd_cfg(struct irq_data *irq_data);
 extern void lock_vector_lock(void);
 extern void unlock_vector_lock(void);
 #ifdef CONFIG_SMP
-extern void send_cleanup_vector(struct irq_cfg *);
+extern void vector_schedule_cleanup(struct irq_cfg *);
 extern void irq_complete_move(struct irq_cfg *cfg);
 #else
-static inline void send_cleanup_vector(struct irq_cfg *c) { }
+static inline void vector_schedule_cleanup(struct irq_cfg *c) { }
 static inline void irq_complete_move(struct irq_cfg *c) { }
 #endif
 
diff --git a/arch/x86/kernel/apic/vector.c b/arch/x86/kernel/apic/vector.c
index c1efebd27e6c..aa370bd0d933 100644
--- a/arch/x86/kernel/apic/vector.c
+++ b/arch/x86/kernel/apic/vector.c
@@ -967,7 +967,7 @@ DEFINE_IDTENTRY_SYSVEC(sysvec_irq_move_cleanup)
 	raw_spin_unlock(&vector_lock);
 }
 
-static void __send_cleanup_vector(struct apic_chip_data *apicd)
+static void __vector_schedule_cleanup(struct apic_chip_data *apicd)
 {
 	unsigned int cpu;
 
@@ -983,13 +983,13 @@ static void __send_cleanup_vector(struct apic_chip_data *apicd)
 	raw_spin_unlock(&vector_lock);
 }
 
-void send_cleanup_vector(struct irq_cfg *cfg)
+void vector_schedule_cleanup(struct irq_cfg *cfg)
 {
 	struct apic_chip_data *apicd;
 
 	apicd = container_of(cfg, struct apic_chip_data, hw_irq_cfg);
 	if (apicd->move_in_progress)
-		__send_cleanup_vector(apicd);
+		__vector_schedule_cleanup(apicd);
 }
 
 void irq_complete_move(struct irq_cfg *cfg)
@@ -1007,7 +1007,7 @@ void irq_complete_move(struct irq_cfg *cfg)
 	 * on the same CPU.
 	 */
 	if (apicd->cpu == smp_processor_id())
-		__send_cleanup_vector(apicd);
+		__vector_schedule_cleanup(apicd);
 }
 
 /*
diff --git a/arch/x86/platform/uv/uv_irq.c b/arch/x86/platform/uv/uv_irq.c
index ee21d6a36a80..4221259a5870 100644
--- a/arch/x86/platform/uv/uv_irq.c
+++ b/arch/x86/platform/uv/uv_irq.c
@@ -58,7 +58,7 @@ uv_set_irq_affinity(struct irq_data *data, const struct cpumask *mask,
 	ret = parent->chip->irq_set_affinity(parent, mask, force);
 	if (ret >= 0) {
 		uv_program_mmr(cfg, data->chip_data);
-		send_cleanup_vector(cfg);
+		vector_schedule_cleanup(cfg);
 	}
 
 	return ret;
diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
index dc1ec6849775..b5900e70de60 100644
--- a/drivers/iommu/amd/iommu.c
+++ b/drivers/iommu/amd/iommu.c
@@ -3658,7 +3658,7 @@ static int amd_ir_set_affinity(struct irq_data *data,
 	 * at the new destination. So, time to cleanup the previous
 	 * vector allocation.
 	 */
-	send_cleanup_vector(cfg);
+	vector_schedule_cleanup(cfg);
 
 	return IRQ_SET_MASK_OK_DONE;
 }
diff --git a/drivers/iommu/hyperv-iommu.c b/drivers/iommu/hyperv-iommu.c
index 8302db7f783e..8a5c17b97310 100644
--- a/drivers/iommu/hyperv-iommu.c
+++ b/drivers/iommu/hyperv-iommu.c
@@ -51,7 +51,7 @@ static int hyperv_ir_set_affinity(struct irq_data *data,
 	if (ret < 0 || ret == IRQ_SET_MASK_OK_DONE)
 		return ret;
 
-	send_cleanup_vector(cfg);
+	vector_schedule_cleanup(cfg);
 
 	return 0;
 }
@@ -257,7 +257,7 @@ static int hyperv_root_ir_set_affinity(struct irq_data *data,
 	if (ret < 0 || ret == IRQ_SET_MASK_OK_DONE)
 		return ret;
 
-	send_cleanup_vector(cfg);
+	vector_schedule_cleanup(cfg);
 
 	return 0;
 }
diff --git a/drivers/iommu/intel/irq_remapping.c b/drivers/iommu/intel/irq_remapping.c
index a1b987335b31..55d899f5a14b 100644
--- a/drivers/iommu/intel/irq_remapping.c
+++ b/drivers/iommu/intel/irq_remapping.c
@@ -1180,7 +1180,7 @@ intel_ir_set_affinity(struct irq_data *data, const struct cpumask *mask,
 	 * at the new destination. So, time to cleanup the previous
 	 * vector allocation.
 	 */
-	send_cleanup_vector(cfg);
+	vector_schedule_cleanup(cfg);
 
 	return IRQ_SET_MASK_OK_DONE;
 }
-- 
2.34.1

[PATCH v2 2/3] x86/vector: Replace IRQ_MOVE_CLEANUP_VECTOR with a timer callback

[Xin Li]

From: Thomas Gleixner <tglx@linutronix.de>

Replace IRQ_MOVE_CLEANUP_VECTOR with a timer callback for cleaning
up the leftovers of a moved interrupt.

The only new job incurred is to do vector cleanup in lapic_offline()
in case the vector cleanup timer has not expired.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Xin Li <xin3.li@intel.com>
---

Changes since v1:
* Add a lockdep_assert_held() statement to get rid of a bad comment
  that claims __vector_cleanup() needs to be called with vector_lock
  held. (Peter Zijlstra).
---
 arch/x86/include/asm/idtentry.h    |  1 -
 arch/x86/include/asm/irq_vectors.h |  7 ---
 arch/x86/kernel/apic/vector.c      | 98 ++++++++++++++++++++++++------
 arch/x86/kernel/idt.c              |  1 -
 4 files changed, 78 insertions(+), 29 deletions(-)

diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h
index b241af4ce9b4..cd5c10a74071 100644
--- a/arch/x86/include/asm/idtentry.h
+++ b/arch/x86/include/asm/idtentry.h
@@ -648,7 +648,6 @@ DECLARE_IDTENTRY_SYSVEC(X86_PLATFORM_IPI_VECTOR,	sysvec_x86_platform_ipi);
 
 #ifdef CONFIG_SMP
 DECLARE_IDTENTRY(RESCHEDULE_VECTOR,			sysvec_reschedule_ipi);
-DECLARE_IDTENTRY_SYSVEC(IRQ_MOVE_CLEANUP_VECTOR,	sysvec_irq_move_cleanup);
 DECLARE_IDTENTRY_SYSVEC(REBOOT_VECTOR,			sysvec_reboot);
 DECLARE_IDTENTRY_SYSVEC(CALL_FUNCTION_SINGLE_VECTOR,	sysvec_call_function_single);
 DECLARE_IDTENTRY_SYSVEC(CALL_FUNCTION_VECTOR,		sysvec_call_function);
diff --git a/arch/x86/include/asm/irq_vectors.h b/arch/x86/include/asm/irq_vectors.h
index 43dcb9284208..3a19904c2db6 100644
--- a/arch/x86/include/asm/irq_vectors.h
+++ b/arch/x86/include/asm/irq_vectors.h
@@ -35,13 +35,6 @@
  */
 #define FIRST_EXTERNAL_VECTOR		0x20
 
-/*
- * Reserve the lowest usable vector (and hence lowest priority)  0x20 for
- * triggering cleanup after irq migration. 0x21-0x2f will still be used
- * for device interrupts.
- */
-#define IRQ_MOVE_CLEANUP_VECTOR		FIRST_EXTERNAL_VECTOR
-
 #define IA32_SYSCALL_VECTOR		0x80
 
 /*
diff --git a/arch/x86/kernel/apic/vector.c b/arch/x86/kernel/apic/vector.c
index aa370bd0d933..01c359a66b04 100644
--- a/arch/x86/kernel/apic/vector.c
+++ b/arch/x86/kernel/apic/vector.c
@@ -44,7 +44,18 @@ static cpumask_var_t vector_searchmask;
 static struct irq_chip lapic_controller;
 static struct irq_matrix *vector_matrix;
 #ifdef CONFIG_SMP
-static DEFINE_PER_CPU(struct hlist_head, cleanup_list);
+
+static void vector_cleanup_callback(struct timer_list *tmr);
+
+struct vector_cleanup {
+	struct hlist_head	head;
+	struct timer_list	timer;
+};
+
+static DEFINE_PER_CPU(struct vector_cleanup, vector_cleanup) = {
+	.head	= HLIST_HEAD_INIT,
+	.timer	= __TIMER_INITIALIZER(vector_cleanup_callback, TIMER_PINNED),
+};
 #endif
 
 void lock_vector_lock(void)
@@ -841,10 +852,21 @@ void lapic_online(void)
 		this_cpu_write(vector_irq[vector], __setup_vector_irq(vector));
 }
 
+static void __vector_cleanup(struct vector_cleanup *cl, bool check_irr);
+
 void lapic_offline(void)
 {
+	struct vector_cleanup *cl = this_cpu_ptr(&vector_cleanup);
+
 	lock_vector_lock();
+
+	/* In case the vector cleanup timer has not expired */
+	__vector_cleanup(cl, false);
+
 	irq_matrix_offline(vector_matrix);
+	WARN_ON_ONCE(try_to_del_timer_sync(&cl->timer) < 0);
+	WARN_ON_ONCE(!hlist_empty(&cl->head));
+
 	unlock_vector_lock();
 }
 
@@ -934,49 +956,85 @@ static void free_moved_vector(struct apic_chip_data *apicd)
 	apicd->move_in_progress = 0;
 }
 
-DEFINE_IDTENTRY_SYSVEC(sysvec_irq_move_cleanup)
+static void __vector_cleanup(struct vector_cleanup *cl, bool check_irr)
 {
-	struct hlist_head *clhead = this_cpu_ptr(&cleanup_list);
 	struct apic_chip_data *apicd;
 	struct hlist_node *tmp;
+	bool rearm = false;
 
-	ack_APIC_irq();
-	/* Prevent vectors vanishing under us */
-	raw_spin_lock(&vector_lock);
+	lockdep_assert_held(&vector_lock);
 
-	hlist_for_each_entry_safe(apicd, tmp, clhead, clist) {
+	hlist_for_each_entry_safe(apicd, tmp, &cl->head, clist) {
 		unsigned int irr, vector = apicd->prev_vector;
 
 		/*
 		 * Paranoia: Check if the vector that needs to be cleaned
-		 * up is registered at the APICs IRR. If so, then this is
-		 * not the best time to clean it up. Clean it up in the
-		 * next attempt by sending another IRQ_MOVE_CLEANUP_VECTOR
-		 * to this CPU. IRQ_MOVE_CLEANUP_VECTOR is the lowest
-		 * priority external vector, so on return from this
-		 * interrupt the device interrupt will happen first.
+		 * up is registered at the APICs IRR. That's clearly a
+		 * hardware issue if the vector arrived on the old target
+		 * _after_ interrupts were disabled above. Keep @apicd
+		 * on the list and schedule the timer again to give the CPU
+		 * a chance to handle the pending interrupt.
+		 *
+		 * Do not check IRR when called from lapic_offline(), because
+		 * fixup_irqs() was just called to scan IRR for set bits and
+		 * forward them to new destination CPUs via IPIs.
 		 */
-		irr = apic_read(APIC_IRR + (vector / 32 * 0x10));
+		irr = check_irr ? apic_read(APIC_IRR + (vector / 32 * 0x10)) : 0;
 		if (irr & (1U << (vector % 32))) {
-			apic->send_IPI_self(IRQ_MOVE_CLEANUP_VECTOR);
+			pr_warn_once("Moved interrupt pending in old target APIC %u\n", apicd->irq);
+			rearm = true;
 			continue;
 		}
 		free_moved_vector(apicd);
 	}
 
-	raw_spin_unlock(&vector_lock);
+	/*
+	 * Must happen under vector_lock to make the timer_pending() check
+	 * in __vector_schedule_cleanup() race free against the rearm here.
+	 */
+	if (rearm)
+		mod_timer(&cl->timer, jiffies + 1);
+}
+
+static void vector_cleanup_callback(struct timer_list *tmr)
+{
+	struct vector_cleanup *cl = container_of(tmr, typeof(*cl), timer);
+
+	/* Prevent vectors vanishing under us */
+	raw_spin_lock_irq(&vector_lock);
+	__vector_cleanup(cl, true);
+	raw_spin_unlock_irq(&vector_lock);
 }
 
 static void __vector_schedule_cleanup(struct apic_chip_data *apicd)
 {
-	unsigned int cpu;
+	unsigned int cpu = apicd->prev_cpu;
 
 	raw_spin_lock(&vector_lock);
 	apicd->move_in_progress = 0;
-	cpu = apicd->prev_cpu;
 	if (cpu_online(cpu)) {
-		hlist_add_head(&apicd->clist, per_cpu_ptr(&cleanup_list, cpu));
-		apic->send_IPI(cpu, IRQ_MOVE_CLEANUP_VECTOR);
+		struct vector_cleanup *cl = per_cpu_ptr(&vector_cleanup, cpu);
+
+		hlist_add_head(&apicd->clist, &cl->head);
+
+		/*
+		 * The lockless timer_pending() check is safe here. If it
+		 * returns true, then the callback will observe this new
+		 * apic data in the hlist as everything is serialized by
+		 * vector lock.
+		 *
+		 * If it returns false then the timer is either not armed
+		 * or the other CPU executes the callback, which again
+		 * would be blocked on vector lock. Rearming it in the
+		 * latter case makes it fire for nothing.
+		 *
+		 * This is also safe against the callback rearming the timer
+		 * because that's serialized via vector lock too.
+		 */
+		if (!timer_pending(&cl->timer)) {
+			cl->timer.expires = jiffies + 1;
+			add_timer_on(&cl->timer, cpu);
+		}
 	} else {
 		apicd->prev_vector = 0;
 	}
diff --git a/arch/x86/kernel/idt.c b/arch/x86/kernel/idt.c
index a58c6bc1cd68..f3958262c725 100644
--- a/arch/x86/kernel/idt.c
+++ b/arch/x86/kernel/idt.c
@@ -131,7 +131,6 @@ static const __initconst struct idt_data apic_idts[] = {
 	INTG(RESCHEDULE_VECTOR,			asm_sysvec_reschedule_ipi),
 	INTG(CALL_FUNCTION_VECTOR,		asm_sysvec_call_function),
 	INTG(CALL_FUNCTION_SINGLE_VECTOR,	asm_sysvec_call_function_single),
-	INTG(IRQ_MOVE_CLEANUP_VECTOR,		asm_sysvec_irq_move_cleanup),
 	INTG(REBOOT_VECTOR,			asm_sysvec_reboot),
 #endif
 
-- 
2.34.1

[PATCH v2 3/3] tools: Get rid of IRQ_MOVE_CLEANUP_VECTOR from tools

[Xin Li]

Get rid of IRQ_MOVE_CLEANUP_VECTOR from tools.

Signed-off-by: Xin Li <xin3.li@intel.com>
---
 tools/arch/x86/include/asm/irq_vectors.h               | 7 -------
 tools/perf/trace/beauty/tracepoints/x86_irq_vectors.sh | 2 +-
 2 files changed, 1 insertion(+), 8 deletions(-)

diff --git a/tools/arch/x86/include/asm/irq_vectors.h b/tools/arch/x86/include/asm/irq_vectors.h
index 43dcb9284208..3a19904c2db6 100644
--- a/tools/arch/x86/include/asm/irq_vectors.h
+++ b/tools/arch/x86/include/asm/irq_vectors.h
@@ -35,13 +35,6 @@
  */
 #define FIRST_EXTERNAL_VECTOR		0x20
 
-/*
- * Reserve the lowest usable vector (and hence lowest priority)  0x20 for
- * triggering cleanup after irq migration. 0x21-0x2f will still be used
- * for device interrupts.
- */
-#define IRQ_MOVE_CLEANUP_VECTOR		FIRST_EXTERNAL_VECTOR
-
 #define IA32_SYSCALL_VECTOR		0x80
 
 /*
diff --git a/tools/perf/trace/beauty/tracepoints/x86_irq_vectors.sh b/tools/perf/trace/beauty/tracepoints/x86_irq_vectors.sh
index eed9ce0fcbe6..87dc68c7de0c 100755
--- a/tools/perf/trace/beauty/tracepoints/x86_irq_vectors.sh
+++ b/tools/perf/trace/beauty/tracepoints/x86_irq_vectors.sh
@@ -12,7 +12,7 @@ x86_irq_vectors=${arch_x86_header_dir}/irq_vectors.h
 
 # FIRST_EXTERNAL_VECTOR is not that useful, find what is its number
 # and then replace whatever is using it and that is useful, which at
-# the time of writing of this script was: IRQ_MOVE_CLEANUP_VECTOR.
+# the time of writing of this script was: 0x20.
 
 first_external_regex='^#define[[:space:]]+FIRST_EXTERNAL_VECTOR[[:space:]]+(0x[[:xdigit:]]+)$'
 first_external_vector=$(grep -E ${first_external_regex} ${x86_irq_vectors} | sed -r "s/${first_external_regex}/\1/g")
-- 
2.34.1

[tip: x86/apic] tools: Get rid of IRQ_MOVE_CLEANUP_VECTOR from tools

[tip-bot2 for Xin Li]

The following commit has been merged into the x86/apic branch of tip:

Commit-ID:     6e3edb0fb5c0ee3ab1edc1fcfd159e7dd177ef0e
Gitweb:        https://git.kernel.org/tip/6e3edb0fb5c0ee3ab1edc1fcfd159e7dd177ef0e
Author:        Xin Li <xin3.li@intel.com>
AuthorDate:    Wed, 21 Jun 2023 10:12:48 -07:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Sun, 06 Aug 2023 14:15:10 +02:00

tools: Get rid of IRQ_MOVE_CLEANUP_VECTOR from tools

IRQ_MOVE_CLEANUP_VECTOR is not longer in use. Remove the last traces.

Signed-off-by: Xin Li <xin3.li@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20230621171248.6805-4-xin3.li@intel.com

---
 tools/arch/x86/include/asm/irq_vectors.h               | 7 -------
 tools/perf/trace/beauty/tracepoints/x86_irq_vectors.sh | 2 +-
 2 files changed, 1 insertion(+), 8 deletions(-)

diff --git a/tools/arch/x86/include/asm/irq_vectors.h b/tools/arch/x86/include/asm/irq_vectors.h
index 43dcb92..3a19904 100644
--- a/tools/arch/x86/include/asm/irq_vectors.h
+++ b/tools/arch/x86/include/asm/irq_vectors.h
@@ -35,13 +35,6 @@
  */
 #define FIRST_EXTERNAL_VECTOR		0x20
 
-/*
- * Reserve the lowest usable vector (and hence lowest priority)  0x20 for
- * triggering cleanup after irq migration. 0x21-0x2f will still be used
- * for device interrupts.
- */
-#define IRQ_MOVE_CLEANUP_VECTOR		FIRST_EXTERNAL_VECTOR
-
 #define IA32_SYSCALL_VECTOR		0x80
 
 /*
diff --git a/tools/perf/trace/beauty/tracepoints/x86_irq_vectors.sh b/tools/perf/trace/beauty/tracepoints/x86_irq_vectors.sh
index eed9ce0..87dc68c 100755
--- a/tools/perf/trace/beauty/tracepoints/x86_irq_vectors.sh
+++ b/tools/perf/trace/beauty/tracepoints/x86_irq_vectors.sh
@@ -12,7 +12,7 @@ x86_irq_vectors=${arch_x86_header_dir}/irq_vectors.h
 
 # FIRST_EXTERNAL_VECTOR is not that useful, find what is its number
 # and then replace whatever is using it and that is useful, which at
-# the time of writing of this script was: IRQ_MOVE_CLEANUP_VECTOR.
+# the time of writing of this script was: 0x20.
 
 first_external_regex='^#define[[:space:]]+FIRST_EXTERNAL_VECTOR[[:space:]]+(0x[[:xdigit:]]+)$'
 first_external_vector=$(grep -E ${first_external_regex} ${x86_irq_vectors} | sed -r "s/${first_external_regex}/\1/g")

[tip: x86/apic] x86/vector: Replace IRQ_MOVE_CLEANUP_VECTOR with a timer callback

[tip-bot2 for Thomas Gleixner]

The following commit has been merged into the x86/apic branch of tip:

Commit-ID:     bdc1dad299bb1d38ce329de0dad0beadc76badf4
Gitweb:        https://git.kernel.org/tip/bdc1dad299bb1d38ce329de0dad0beadc76badf4
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Wed, 21 Jun 2023 10:12:47 -07:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Sun, 06 Aug 2023 14:15:10 +02:00

x86/vector: Replace IRQ_MOVE_CLEANUP_VECTOR with a timer callback

The left overs of a moved interrupt are cleaned up once the interrupt is
raised on the new target CPU. Keeping the vector valid on the original
target CPU guarantees that there can't be an interrupt lost if the affinity
change races with an concurrent interrupt from the device.

This cleanup utilizes the lowest priority interrupt vector for this
cleanup, which makes sure that in the unlikely case when the to be cleaned
up interrupt is pending in the local APICs IRR the cleanup vector does not
live lock.

But there is no real reason to use an interrupt vector for cleaning up the
leftovers of a moved interrupt. It's not a high performance operation. The
only requirement is that it happens on the original target CPU.

Convert it to use a timer instead and adjust the code accordingly.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Xin Li <xin3.li@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20230621171248.6805-3-xin3.li@intel.com

---
 arch/x86/include/asm/idtentry.h    |  1 +-
 arch/x86/include/asm/irq_vectors.h |  7 +--
 arch/x86/kernel/apic/vector.c      | 98 +++++++++++++++++++++++------
 arch/x86/kernel/idt.c              |  1 +-
 4 files changed, 78 insertions(+), 29 deletions(-)

diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h
index b241af4..cd5c10a 100644
--- a/arch/x86/include/asm/idtentry.h
+++ b/arch/x86/include/asm/idtentry.h
@@ -648,7 +648,6 @@ DECLARE_IDTENTRY_SYSVEC(X86_PLATFORM_IPI_VECTOR,	sysvec_x86_platform_ipi);
 
 #ifdef CONFIG_SMP
 DECLARE_IDTENTRY(RESCHEDULE_VECTOR,			sysvec_reschedule_ipi);
-DECLARE_IDTENTRY_SYSVEC(IRQ_MOVE_CLEANUP_VECTOR,	sysvec_irq_move_cleanup);
 DECLARE_IDTENTRY_SYSVEC(REBOOT_VECTOR,			sysvec_reboot);
 DECLARE_IDTENTRY_SYSVEC(CALL_FUNCTION_SINGLE_VECTOR,	sysvec_call_function_single);
 DECLARE_IDTENTRY_SYSVEC(CALL_FUNCTION_VECTOR,		sysvec_call_function);
diff --git a/arch/x86/include/asm/irq_vectors.h b/arch/x86/include/asm/irq_vectors.h
index 43dcb92..3a19904 100644
--- a/arch/x86/include/asm/irq_vectors.h
+++ b/arch/x86/include/asm/irq_vectors.h
@@ -35,13 +35,6 @@
  */
 #define FIRST_EXTERNAL_VECTOR		0x20
 
-/*
- * Reserve the lowest usable vector (and hence lowest priority)  0x20 for
- * triggering cleanup after irq migration. 0x21-0x2f will still be used
- * for device interrupts.
- */
-#define IRQ_MOVE_CLEANUP_VECTOR		FIRST_EXTERNAL_VECTOR
-
 #define IA32_SYSCALL_VECTOR		0x80
 
 /*
diff --git a/arch/x86/kernel/apic/vector.c b/arch/x86/kernel/apic/vector.c
index aa370bd..01c359a 100644
--- a/arch/x86/kernel/apic/vector.c
+++ b/arch/x86/kernel/apic/vector.c
@@ -44,7 +44,18 @@ static cpumask_var_t vector_searchmask;
 static struct irq_chip lapic_controller;
 static struct irq_matrix *vector_matrix;
 #ifdef CONFIG_SMP
-static DEFINE_PER_CPU(struct hlist_head, cleanup_list);
+
+static void vector_cleanup_callback(struct timer_list *tmr);
+
+struct vector_cleanup {
+	struct hlist_head	head;
+	struct timer_list	timer;
+};
+
+static DEFINE_PER_CPU(struct vector_cleanup, vector_cleanup) = {
+	.head	= HLIST_HEAD_INIT,
+	.timer	= __TIMER_INITIALIZER(vector_cleanup_callback, TIMER_PINNED),
+};
 #endif
 
 void lock_vector_lock(void)
@@ -841,10 +852,21 @@ void lapic_online(void)
 		this_cpu_write(vector_irq[vector], __setup_vector_irq(vector));
 }
 
+static void __vector_cleanup(struct vector_cleanup *cl, bool check_irr);
+
 void lapic_offline(void)
 {
+	struct vector_cleanup *cl = this_cpu_ptr(&vector_cleanup);
+
 	lock_vector_lock();
+
+	/* In case the vector cleanup timer has not expired */
+	__vector_cleanup(cl, false);
+
 	irq_matrix_offline(vector_matrix);
+	WARN_ON_ONCE(try_to_del_timer_sync(&cl->timer) < 0);
+	WARN_ON_ONCE(!hlist_empty(&cl->head));
+
 	unlock_vector_lock();
 }
 
@@ -934,49 +956,85 @@ static void free_moved_vector(struct apic_chip_data *apicd)
 	apicd->move_in_progress = 0;
 }
 
-DEFINE_IDTENTRY_SYSVEC(sysvec_irq_move_cleanup)
+static void __vector_cleanup(struct vector_cleanup *cl, bool check_irr)
 {
-	struct hlist_head *clhead = this_cpu_ptr(&cleanup_list);
 	struct apic_chip_data *apicd;
 	struct hlist_node *tmp;
+	bool rearm = false;
 
-	ack_APIC_irq();
-	/* Prevent vectors vanishing under us */
-	raw_spin_lock(&vector_lock);
+	lockdep_assert_held(&vector_lock);
 
-	hlist_for_each_entry_safe(apicd, tmp, clhead, clist) {
+	hlist_for_each_entry_safe(apicd, tmp, &cl->head, clist) {
 		unsigned int irr, vector = apicd->prev_vector;
 
 		/*
 		 * Paranoia: Check if the vector that needs to be cleaned
-		 * up is registered at the APICs IRR. If so, then this is
-		 * not the best time to clean it up. Clean it up in the
-		 * next attempt by sending another IRQ_MOVE_CLEANUP_VECTOR
-		 * to this CPU. IRQ_MOVE_CLEANUP_VECTOR is the lowest
-		 * priority external vector, so on return from this
-		 * interrupt the device interrupt will happen first.
+		 * up is registered at the APICs IRR. That's clearly a
+		 * hardware issue if the vector arrived on the old target
+		 * _after_ interrupts were disabled above. Keep @apicd
+		 * on the list and schedule the timer again to give the CPU
+		 * a chance to handle the pending interrupt.
+		 *
+		 * Do not check IRR when called from lapic_offline(), because
+		 * fixup_irqs() was just called to scan IRR for set bits and
+		 * forward them to new destination CPUs via IPIs.
 		 */
-		irr = apic_read(APIC_IRR + (vector / 32 * 0x10));
+		irr = check_irr ? apic_read(APIC_IRR + (vector / 32 * 0x10)) : 0;
 		if (irr & (1U << (vector % 32))) {
-			apic->send_IPI_self(IRQ_MOVE_CLEANUP_VECTOR);
+			pr_warn_once("Moved interrupt pending in old target APIC %u\n", apicd->irq);
+			rearm = true;
 			continue;
 		}
 		free_moved_vector(apicd);
 	}
 
-	raw_spin_unlock(&vector_lock);
+	/*
+	 * Must happen under vector_lock to make the timer_pending() check
+	 * in __vector_schedule_cleanup() race free against the rearm here.
+	 */
+	if (rearm)
+		mod_timer(&cl->timer, jiffies + 1);
+}
+
+static void vector_cleanup_callback(struct timer_list *tmr)
+{
+	struct vector_cleanup *cl = container_of(tmr, typeof(*cl), timer);
+
+	/* Prevent vectors vanishing under us */
+	raw_spin_lock_irq(&vector_lock);
+	__vector_cleanup(cl, true);
+	raw_spin_unlock_irq(&vector_lock);
 }
 
 static void __vector_schedule_cleanup(struct apic_chip_data *apicd)
 {
-	unsigned int cpu;
+	unsigned int cpu = apicd->prev_cpu;
 
 	raw_spin_lock(&vector_lock);
 	apicd->move_in_progress = 0;
-	cpu = apicd->prev_cpu;
 	if (cpu_online(cpu)) {
-		hlist_add_head(&apicd->clist, per_cpu_ptr(&cleanup_list, cpu));
-		apic->send_IPI(cpu, IRQ_MOVE_CLEANUP_VECTOR);
+		struct vector_cleanup *cl = per_cpu_ptr(&vector_cleanup, cpu);
+
+		hlist_add_head(&apicd->clist, &cl->head);
+
+		/*
+		 * The lockless timer_pending() check is safe here. If it
+		 * returns true, then the callback will observe this new
+		 * apic data in the hlist as everything is serialized by
+		 * vector lock.
+		 *
+		 * If it returns false then the timer is either not armed
+		 * or the other CPU executes the callback, which again
+		 * would be blocked on vector lock. Rearming it in the
+		 * latter case makes it fire for nothing.
+		 *
+		 * This is also safe against the callback rearming the timer
+		 * because that's serialized via vector lock too.
+		 */
+		if (!timer_pending(&cl->timer)) {
+			cl->timer.expires = jiffies + 1;
+			add_timer_on(&cl->timer, cpu);
+		}
 	} else {
 		apicd->prev_vector = 0;
 	}
diff --git a/arch/x86/kernel/idt.c b/arch/x86/kernel/idt.c
index a58c6bc..f395826 100644
--- a/arch/x86/kernel/idt.c
+++ b/arch/x86/kernel/idt.c
@@ -131,7 +131,6 @@ static const __initconst struct idt_data apic_idts[] = {
 	INTG(RESCHEDULE_VECTOR,			asm_sysvec_reschedule_ipi),
 	INTG(CALL_FUNCTION_VECTOR,		asm_sysvec_call_function),
 	INTG(CALL_FUNCTION_SINGLE_VECTOR,	asm_sysvec_call_function_single),
-	INTG(IRQ_MOVE_CLEANUP_VECTOR,		asm_sysvec_irq_move_cleanup),
 	INTG(REBOOT_VECTOR,			asm_sysvec_reboot),
 #endif
 

[tip: x86/apic] x86/vector: Rename send_cleanup_vector() to vector_schedule_cleanup()

[tip-bot2 for Thomas Gleixner]

The following commit has been merged into the x86/apic branch of tip:

Commit-ID:     a539cc86a1cb688df24d9cff17d946a8c0b94b38
Gitweb:        https://git.kernel.org/tip/a539cc86a1cb688df24d9cff17d946a8c0b94b38
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Wed, 21 Jun 2023 10:12:46 -07:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Sun, 06 Aug 2023 14:15:09 +02:00

x86/vector: Rename send_cleanup_vector() to vector_schedule_cleanup()

Rename send_cleanup_vector() to vector_schedule_cleanup() to prepare for
replacing the vector cleanup IPI with a timer callback.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Xin Li <xin3.li@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Steve Wahl <steve.wahl@hpe.com>
Link: https://lore.kernel.org/r/20230621171248.6805-2-xin3.li@intel.com

---
 arch/x86/include/asm/hw_irq.h       | 4 ++--
 arch/x86/kernel/apic/vector.c       | 8 ++++----
 arch/x86/platform/uv/uv_irq.c       | 2 +-
 drivers/iommu/amd/iommu.c           | 2 +-
 drivers/iommu/hyperv-iommu.c        | 4 ++--
 drivers/iommu/intel/irq_remapping.c | 2 +-
 6 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/arch/x86/include/asm/hw_irq.h b/arch/x86/include/asm/hw_irq.h
index d465ece..5518298 100644
--- a/arch/x86/include/asm/hw_irq.h
+++ b/arch/x86/include/asm/hw_irq.h
@@ -97,10 +97,10 @@ extern struct irq_cfg *irqd_cfg(struct irq_data *irq_data);
 extern void lock_vector_lock(void);
 extern void unlock_vector_lock(void);
 #ifdef CONFIG_SMP
-extern void send_cleanup_vector(struct irq_cfg *);
+extern void vector_schedule_cleanup(struct irq_cfg *);
 extern void irq_complete_move(struct irq_cfg *cfg);
 #else
-static inline void send_cleanup_vector(struct irq_cfg *c) { }
+static inline void vector_schedule_cleanup(struct irq_cfg *c) { }
 static inline void irq_complete_move(struct irq_cfg *c) { }
 #endif
 
diff --git a/arch/x86/kernel/apic/vector.c b/arch/x86/kernel/apic/vector.c
index c1efebd..aa370bd 100644
--- a/arch/x86/kernel/apic/vector.c
+++ b/arch/x86/kernel/apic/vector.c
@@ -967,7 +967,7 @@ DEFINE_IDTENTRY_SYSVEC(sysvec_irq_move_cleanup)
 	raw_spin_unlock(&vector_lock);
 }
 
-static void __send_cleanup_vector(struct apic_chip_data *apicd)
+static void __vector_schedule_cleanup(struct apic_chip_data *apicd)
 {
 	unsigned int cpu;
 
@@ -983,13 +983,13 @@ static void __send_cleanup_vector(struct apic_chip_data *apicd)
 	raw_spin_unlock(&vector_lock);
 }
 
-void send_cleanup_vector(struct irq_cfg *cfg)
+void vector_schedule_cleanup(struct irq_cfg *cfg)
 {
 	struct apic_chip_data *apicd;
 
 	apicd = container_of(cfg, struct apic_chip_data, hw_irq_cfg);
 	if (apicd->move_in_progress)
-		__send_cleanup_vector(apicd);
+		__vector_schedule_cleanup(apicd);
 }
 
 void irq_complete_move(struct irq_cfg *cfg)
@@ -1007,7 +1007,7 @@ void irq_complete_move(struct irq_cfg *cfg)
 	 * on the same CPU.
 	 */
 	if (apicd->cpu == smp_processor_id())
-		__send_cleanup_vector(apicd);
+		__vector_schedule_cleanup(apicd);
 }
 
 /*
diff --git a/arch/x86/platform/uv/uv_irq.c b/arch/x86/platform/uv/uv_irq.c
index ee21d6a..4221259 100644
--- a/arch/x86/platform/uv/uv_irq.c
+++ b/arch/x86/platform/uv/uv_irq.c
@@ -58,7 +58,7 @@ uv_set_irq_affinity(struct irq_data *data, const struct cpumask *mask,
 	ret = parent->chip->irq_set_affinity(parent, mask, force);
 	if (ret >= 0) {
 		uv_program_mmr(cfg, data->chip_data);
-		send_cleanup_vector(cfg);
+		vector_schedule_cleanup(cfg);
 	}
 
 	return ret;
diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
index c3b58a8..7d7d379 100644
--- a/drivers/iommu/amd/iommu.c
+++ b/drivers/iommu/amd/iommu.c
@@ -3681,7 +3681,7 @@ static int amd_ir_set_affinity(struct irq_data *data,
 	 * at the new destination. So, time to cleanup the previous
 	 * vector allocation.
 	 */
-	send_cleanup_vector(cfg);
+	vector_schedule_cleanup(cfg);
 
 	return IRQ_SET_MASK_OK_DONE;
 }
diff --git a/drivers/iommu/hyperv-iommu.c b/drivers/iommu/hyperv-iommu.c
index 8302db7..8a5c17b 100644
--- a/drivers/iommu/hyperv-iommu.c
+++ b/drivers/iommu/hyperv-iommu.c
@@ -51,7 +51,7 @@ static int hyperv_ir_set_affinity(struct irq_data *data,
 	if (ret < 0 || ret == IRQ_SET_MASK_OK_DONE)
 		return ret;
 
-	send_cleanup_vector(cfg);
+	vector_schedule_cleanup(cfg);
 
 	return 0;
 }
@@ -257,7 +257,7 @@ static int hyperv_root_ir_set_affinity(struct irq_data *data,
 	if (ret < 0 || ret == IRQ_SET_MASK_OK_DONE)
 		return ret;
 
-	send_cleanup_vector(cfg);
+	vector_schedule_cleanup(cfg);
 
 	return 0;
 }
diff --git a/drivers/iommu/intel/irq_remapping.c b/drivers/iommu/intel/irq_remapping.c
index 08f5632..29b9e55 100644
--- a/drivers/iommu/intel/irq_remapping.c
+++ b/drivers/iommu/intel/irq_remapping.c
@@ -1176,7 +1176,7 @@ intel_ir_set_affinity(struct irq_data *data, const struct cpumask *mask,
 	 * at the new destination. So, time to cleanup the previous
 	 * vector allocation.
 	 */
-	send_cleanup_vector(cfg);
+	vector_schedule_cleanup(cfg);
 
 	return IRQ_SET_MASK_OK_DONE;
 }