Merge tag 'x86-irq-2026-02-09' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 irq updates from Thomas Gleixner:
 "Trivial cleanups for the posted MSI interrupt handling"

* tag 'x86-irq-2026-02-09' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/irq_remapping: Sanitize posted_msi_supported()
  x86/irq: Cleanup posted MSI code

Author: torvalds

arch/x86/include/asm/irq_remapping.h

@@ -67,9 +67,10 @@ static inline struct irq_domain *arch_get_ir_parent_domain(void)
 
 extern bool enable_posted_msi;
 
-static inline bool posted_msi_supported(void)
+static inline bool posted_msi_enabled(void)
 {
-	return enable_posted_msi && irq_remapping_cap(IRQ_POSTING_CAP);
+	return IS_ENABLED(CONFIG_X86_POSTED_MSI) &&
+		enable_posted_msi && irq_remapping_cap(IRQ_POSTING_CAP);
 }
 
 #else  /* CONFIG_IRQ_REMAP */

arch/x86/kernel/irq.c

@@ -420,11 +420,9 @@ static DEFINE_PER_CPU_CACHE_HOT(bool, posted_msi_handler_active);
 
 void intel_posted_msi_init(void)
 {
-	u32 destination;
-	u32 apic_id;
+	u32 destination, apic_id;
 
 	this_cpu_write(posted_msi_pi_desc.nv, POSTED_MSI_NOTIFICATION_VECTOR);
-
 	/*
 	 * APIC destination ID is stored in bit 8:15 while in XAPIC mode.
 	 * VT-d spec. CH 9.11
@@ -468,8 +466,8 @@ static __always_inline bool handle_pending_pir(unsigned long *pir, struct pt_reg
 }
 
 /*
- * Performance data shows that 3 is good enough to harvest 90+% of the benefit
- * on high IRQ rate workload.
+ * Performance data shows that 3 is good enough to harvest 90+% of the
+ * benefit on high interrupt rate workloads.
  */
 #define MAX_POSTED_MSI_COALESCING_LOOP 3
 
@@ -479,37 +477,34 @@ static __always_inline bool handle_pending_pir(unsigned long *pir, struct pt_reg
  */
 DEFINE_IDTENTRY_SYSVEC(sysvec_posted_msi_notification)
 {
+	struct pi_desc *pid = this_cpu_ptr(&posted_msi_pi_desc);
 	struct pt_regs *old_regs = set_irq_regs(regs);
-	struct pi_desc *pid;
-	int i = 0;
-
-	pid = this_cpu_ptr(&posted_msi_pi_desc);
 
 	/* Mark the handler active for intel_ack_posted_msi_irq() */
 	__this_cpu_write(posted_msi_handler_active, true);
 	inc_irq_stat(posted_msi_notification_count);
 	irq_enter();
 
 	/*
-	 * Max coalescing count includes the extra round of handle_pending_pir
-	 * after clearing the outstanding notification bit. Hence, at most
-	 * MAX_POSTED_MSI_COALESCING_LOOP - 1 loops are executed here.
+	 * Loop only MAX_POSTED_MSI_COALESCING_LOOP - 1 times here to take
+	 * the final handle_pending_pir() invocation after clearing the
+	 * outstanding notification bit into account.
 	 */
-	while (++i < MAX_POSTED_MSI_COALESCING_LOOP) {
+	for (int i = 1; i < MAX_POSTED_MSI_COALESCING_LOOP; i++) {
 		if (!handle_pending_pir(pid->pir, regs))
 			break;
 	}
 
 	/*
-	 * Clear outstanding notification bit to allow new IRQ notifications,
-	 * do this last to maximize the window of interrupt coalescing.
+	 * Clear the outstanding notification bit to rearm the notification
+	 * mechanism.
 	 */
 	pi_clear_on(pid);
 
 	/*
-	 * There could be a race of PI notification and the clearing of ON bit,
-	 * process PIR bits one last time such that handling the new interrupts
-	 * are not delayed until the next IRQ.
+	 * Clearing the ON bit can race with a notification. Process the
+	 * PIR bits one last time so that handling the new interrupts is
+	 * not delayed until the next notification happens.
 	 */
 	handle_pending_pir(pid->pir, regs);
 

drivers/iommu/intel/irq_remapping.c

@@ -1368,7 +1368,7 @@ static void intel_irq_remapping_prepare_irte(struct intel_ir_data *data,
 		break;
 	case X86_IRQ_ALLOC_TYPE_PCI_MSI:
 	case X86_IRQ_ALLOC_TYPE_PCI_MSIX:
-		if (posted_msi_supported()) {
+		if (posted_msi_enabled()) {
 			prepare_irte_posted(irte);
 			data->irq_2_iommu.posted_msi = 1;
 		}
@@ -1460,7 +1460,7 @@ static int intel_irq_remapping_alloc(struct irq_domain *domain,
 
 		irq_data->hwirq = (index << 16) + i;
 		irq_data->chip_data = ird;
-		if (posted_msi_supported() &&
+		if (posted_msi_enabled() &&
 		    ((info->type == X86_IRQ_ALLOC_TYPE_PCI_MSI) ||
 		     (info->type == X86_IRQ_ALLOC_TYPE_PCI_MSIX)))
 			irq_data->chip = &intel_ir_chip_post_msi;