Merge tag 'irq-core-2024-11-18' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull interrupt subsystem updates from Thomas Gleixner:
 "Tree wide:

   - Make nr_irqs static to the core code and provide accessor functions
     to remove existing and prevent future aliasing problems with local
     variables or function arguments of the same name.

  Core code:

   - Prevent freeing an interrupt in the devres code which is not
     managed by devres in the first place.

   - Use seq_put_decimal_ull_width() for decimal values output in
     /proc/interrupts which increases performance significantly as it
     avoids parsing the format strings over and over.

   - Optimize raising the timer and hrtimer soft interrupts by using the
     'set bit only' variants instead of the combined version which
     checks whether ksoftirqd should be woken up. The latter is a
     pointless exercise as both soft interrupts are raised in the
     context of the timer interrupt and therefore never wake up
     ksoftirqd.

   - Delegate timer/hrtimer soft interrupt processing to a dedicated
     thread on RT.

     Timer and hrtimer soft interrupts are always processed in ksoftirqd
     on RT enabled kernels. This can lead to high latencies when other
     soft interrupts are delegated to ksoftirqd as well.

     The separate thread allows to run them seperately under a RT
     scheduling policy to reduce the latency overhead.

  Drivers:

   - New drivers or extensions of existing drivers to support Renesas
     RZ/V2H(P), Aspeed AST27XX, T-HEAD C900 and ATMEL sam9x7 interrupt
     chips

   - Support for multi-cluster GICs on MIPS.

     MIPS CPUs can come with multiple CPU clusters, where each CPU
     cluster has its own GIC (Generic Interrupt Controller). This
     requires to access the GIC of a remote cluster through a redirect
     register block.

     This is encapsulated into a set of helper functions to keep the
     complexity out of the actual code paths which handle the GIC
     details.

   - Support for encrypted guests in the ARM GICV3 ITS driver

     The ITS page needs to be shared with the hypervisor and therefore
     must be decrypted.

   - Small cleanups and fixes all over the place"

* tag 'irq-core-2024-11-18' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (50 commits)
  irqchip/riscv-aplic: Prevent crash when MSI domain is missing
  genirq/proc: Use seq_put_decimal_ull_width() for decimal values
  softirq: Use a dedicated thread for timer wakeups on PREEMPT_RT.
  timers: Use __raise_softirq_irqoff() to raise the softirq.
  hrtimer: Use __raise_softirq_irqoff() to raise the softirq
  riscv: defconfig: Enable T-HEAD C900 ACLINT SSWI drivers
  irqchip: Add T-HEAD C900 ACLINT SSWI driver
  dt-bindings: interrupt-controller: Add T-HEAD C900 ACLINT SSWI device
  irqchip/stm32mp-exti: Use of_property_present() for non-boolean properties
  irqchip/mips-gic: Fix selection of GENERIC_IRQ_EFFECTIVE_AFF_MASK
  irqchip/mips-gic: Prevent indirect access to clusters without CPU cores
  irqchip/mips-gic: Multi-cluster support
  irqchip/mips-gic: Setup defaults in each cluster
  irqchip/mips-gic: Support multi-cluster in for_each_online_cpu_gic()
  irqchip/mips-gic: Replace open coded online CPU iterations
  genirq/irqdesc: Use str_enabled_disabled() helper in wakeup_show()
  genirq/devres: Don't free interrupt which is not managed by devres
  irqchip/gic-v3-its: Fix over allocation in itt_alloc_pool()
  irqchip/aspeed-intc: Add AST27XX INTC support
  dt-bindings: interrupt-controller: Add support for ASPEED AST27XX INTC
  ...

3 files changed, 69 insertions, 15 deletions

diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index f1d151c03164..a04b73c40173 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -147,6 +147,7 @@ enum cpuhp_state {
 	CPUHP_AP_IRQ_EIOINTC_STARTING,
 	CPUHP_AP_IRQ_AVECINTC_STARTING,
 	CPUHP_AP_IRQ_SIFIVE_PLIC_STARTING,
+	CPUHP_AP_IRQ_THEAD_ACLINT_SSWI_STARTING,
 	CPUHP_AP_IRQ_RISCV_IMSIC_STARTING,
 	CPUHP_AP_IRQ_RISCV_SBI_IPI_STARTING,
 	CPUHP_AP_ARM_MVEBU_COHERENCY,
diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index 457151f9f263..8cd9327e4e78 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -616,6 +616,53 @@ extern void __raise_softirq_irqoff(unsigned int nr);
 extern void raise_softirq_irqoff(unsigned int nr);
 extern void raise_softirq(unsigned int nr);
 
+/*
+ * With forced-threaded interrupts enabled a raised softirq is deferred to
+ * ksoftirqd unless it can be handled within the threaded interrupt. This
+ * affects timer_list timers and hrtimers which are explicitly marked with
+ * HRTIMER_MODE_SOFT.
+ * With PREEMPT_RT enabled more hrtimers are moved to softirq for processing
+ * which includes all timers which are not explicitly marked HRTIMER_MODE_HARD.
+ * Userspace controlled timers (like the clock_nanosleep() interface) is divided
+ * into two categories: Tasks with elevated scheduling policy including
+ * SCHED_{FIFO|RR|DL} and the remaining scheduling policy. The tasks with the
+ * elevated scheduling policy are woken up directly from the HARDIRQ while all
+ * other wake ups are delayed to softirq and so to ksoftirqd.
+ *
+ * The ksoftirqd runs at SCHED_OTHER policy at which it should remain since it
+ * handles the softirq in an overloaded situation (not handled everything
+ * within its last run).
+ * If the timers are handled at SCHED_OTHER priority then they competes with all
+ * other SCHED_OTHER tasks for CPU resources are possibly delayed.
+ * Moving timers softirqs to a low priority SCHED_FIFO thread instead ensures
+ * that timer are performed before scheduling any SCHED_OTHER thread.
+ */
+DECLARE_PER_CPU(struct task_struct *, ktimerd);
+DECLARE_PER_CPU(unsigned long, pending_timer_softirq);
+void raise_ktimers_thread(unsigned int nr);
+
+static inline unsigned int local_timers_pending_force_th(void)
+{
+	return __this_cpu_read(pending_timer_softirq);
+}
+
+static inline void raise_timer_softirq(unsigned int nr)
+{
+	lockdep_assert_in_irq();
+	if (force_irqthreads())
+		raise_ktimers_thread(nr);
+	else
+		__raise_softirq_irqoff(nr);
+}
+
+static inline unsigned int local_timers_pending(void)
+{
+	if (force_irqthreads())
+		return local_timers_pending_force_th();
+	else
+		return local_softirq_pending();
+}
+
 DECLARE_PER_CPU(struct task_struct *, ksoftirqd);
 
 static inline struct task_struct *this_cpu_ksoftirqd(void)
diff --git a/include/linux/irqnr.h b/include/linux/irqnr.h
index 3496baa0b07f..e97206c721a0 100644
--- a/include/linux/irqnr.h
+++ b/include/linux/irqnr.h
@@ -5,30 +5,36 @@
 #include <uapi/linux/irqnr.h>
 
 
-extern int nr_irqs;
+unsigned int irq_get_nr_irqs(void) __pure;
+unsigned int irq_set_nr_irqs(unsigned int nr);
 extern struct irq_desc *irq_to_desc(unsigned int irq);
 unsigned int irq_get_next_irq(unsigned int offset);
 
-# define for_each_irq_desc(irq, desc)					\
-	for (irq = 0, desc = irq_to_desc(irq); irq < nr_irqs;		\
-	     irq++, desc = irq_to_desc(irq))				\
-		if (!desc)						\
-			;						\
-		else
-
+#define for_each_irq_desc(irq, desc)                                      \
+	for (unsigned int __nr_irqs__ = irq_get_nr_irqs(); __nr_irqs__;   \
+	     __nr_irqs__ = 0)                                             \
+		for (irq = 0, desc = irq_to_desc(irq); irq < __nr_irqs__; \
+		     irq++, desc = irq_to_desc(irq))                      \
+			if (!desc)                                        \
+				;                                         \
+			else
 
 # define for_each_irq_desc_reverse(irq, desc)				\
-	for (irq = nr_irqs - 1, desc = irq_to_desc(irq); irq >= 0;	\
-	     irq--, desc = irq_to_desc(irq))				\
+	for (irq = irq_get_nr_irqs() - 1, desc = irq_to_desc(irq);	\
+	     irq >= 0; irq--, desc = irq_to_desc(irq))			\
 		if (!desc)						\
 			;						\
 		else
 
-# define for_each_active_irq(irq)			\
-	for (irq = irq_get_next_irq(0); irq < nr_irqs;	\
-	     irq = irq_get_next_irq(irq + 1))
+#define for_each_active_irq(irq)                                        \
+	for (unsigned int __nr_irqs__ = irq_get_nr_irqs(); __nr_irqs__; \
+	     __nr_irqs__ = 0)                                           \
+		for (irq = irq_get_next_irq(0); irq < __nr_irqs__;      \
+		     irq = irq_get_next_irq(irq + 1))
 
-#define for_each_irq_nr(irq)                   \
-       for (irq = 0; irq < nr_irqs; irq++)
+#define for_each_irq_nr(irq)                                            \
+	for (unsigned int __nr_irqs__ = irq_get_nr_irqs(); __nr_irqs__; \
+	     __nr_irqs__ = 0)                                           \
+		for (irq = 0; irq < __nr_irqs__; irq++)
 
 #endif