arch/x86: Make irq_offload SMP-safe on x86_64

The irq_offload mechanism was using the same entry of the IDT vector for
all CPUs on SMP systems. This caused race conditions when two CPUs were
doing irq_offload() calls.

This patch addresses that by adding one indirection layer: the
irq_offload() now sets a per CPU entry with the routine and parameter to
be run. Then a software interrupt is generated, and a default handler
will do the appropriate dispatching.

Finally, test "kernel/smp_abort" is enabled for x86 as it should work
now.

Fixes #72172.

Signed-off-by: Ederson de Souza <ederson.desouza@intel.com>

arch/x86/core/intel64/irq_offload.c

@@ -9,6 +9,7 @@
  */
 
 #include <zephyr/kernel.h>
+#include <zephyr/init.h>
 #include <zephyr/irq_offload.h>
 #include <kernel_arch_data.h>
 
@@ -17,12 +18,37 @@
 extern void (*x86_irq_funcs[NR_IRQ_VECTORS])(const void *arg);
 extern const void *x86_irq_args[NR_IRQ_VECTORS];
 
+static void (*irq_offload_funcs[CONFIG_MP_NUM_CPUS])(const void *arg);
+static const void *irq_offload_args[CONFIG_MP_NUM_CPUS];
+
+static void dispatcher(const void *arg)
+{
+	uint8_t cpu_id = _current_cpu->id;
+
+	if (irq_offload_funcs[cpu_id] != NULL) {
+		irq_offload_funcs[cpu_id](irq_offload_args[cpu_id]);
+	}
+}
 
 void arch_irq_offload(irq_offload_routine_t routine, const void *parameter)
 {
-	x86_irq_funcs[CONFIG_IRQ_OFFLOAD_VECTOR - IV_IRQS] = routine;
-	x86_irq_args[CONFIG_IRQ_OFFLOAD_VECTOR - IV_IRQS] = parameter;
+	int key = arch_irq_lock();
+	uint8_t cpu_id = _current_cpu->id;
+
+	irq_offload_funcs[cpu_id] = routine;
+	irq_offload_args[cpu_id] = parameter;
+
 	__asm__ volatile("int %0" : : "i" (CONFIG_IRQ_OFFLOAD_VECTOR)
 			  : "memory");
-	x86_irq_funcs[CONFIG_IRQ_OFFLOAD_VECTOR - IV_IRQS] = NULL;
+
+	arch_irq_unlock(key);
+}
+
+int irq_offload_init(void)
+{
+	x86_irq_funcs[CONFIG_IRQ_OFFLOAD_VECTOR - IV_IRQS] = dispatcher;
+
+	return 0;
 }
+
+SYS_INIT(irq_offload_init, PRE_KERNEL_1, CONFIG_KERNEL_INIT_PRIORITY_DEFAULT);

tests/kernel/smp_abort/testcase.yaml

@@ -1,6 +1,5 @@
 tests:
   kernel.smp_abort:
-    arch_exclude: x86  # Buggy irq_offload(), see #71172
     tags:
       - kernel
       - smp