arch/x86: (Intel64) add scheduler IPI support

Add z_arch_sched_ipi() and such to enable scheduler IPIs when SMP.

Signed-off-by: Charles E. Youse <charles.youse@intel.com>

arch/x86/Kconfig

@@ -45,8 +45,9 @@ config X86_LONGMODE
 	prompt "Run in long (64-bit) mode"
 	default n
 	select 64BIT
-	select USE_SWITCH_SUPPORTED
 	select USE_SWITCH
+	select USE_SWITCH_SUPPORTED
+	select SCHED_IPI_SUPPORTED
 
 config MAX_IRQ_LINES
 	int "Number of IRQ lines"

arch/x86/core/Kconfig.intel64

@@ -32,6 +32,12 @@ config EXCEPTION_STACK_SIZE
 	  support limited call-tree depth and must fit into the low core,
 	  so they are typically smaller than the ISR stacks.
 
+config SCHED_IPI_VECTOR
+	int "IDT vector to use for scheduler IPI"
+	default 33
+	range 33 255
+	depends on SMP
+
 # We should really only have to provide one of the following two values,
 # but a bug in the Zephyr SDK for x86 precludes the use of division in
 # the assembler. For now, we require that these values be specified manually,

arch/x86/core/intel64/irq.c

@@ -4,6 +4,7 @@
  */
 
 #include <kernel.h>
+#include <ksched.h>
 #include <arch/cpu.h>
 #include <kernel_arch_data.h>
 #include <drivers/interrupt_controller/sysapic.h>
@@ -103,3 +104,18 @@ void z_arch_irq_offload(irq_offload_routine_t routine, void *parameter)
 }
 
 #endif /* CONFIG_IRQ_OFFLOAD */
+
+#if defined(CONFIG_SMP)
+
+void z_x86_ipi_setup(void)
+{
+	/*
+	 * z_sched_ipi() doesn't have the same signature as a typical ISR, so
+	 * we fudge it with a cast. the argument is ignored, no harm done.
+	 */
+
+	x86_irq_funcs[CONFIG_SCHED_IPI_VECTOR - IV_IRQS] =
+		(void *) z_sched_ipi;
+}
+
+#endif

arch/x86/core/prep_c.c

@@ -42,5 +42,9 @@ FUNC_NORETURN void z_x86_prep_c(int unused, struct multiboot_info *info)
 			    true);
 #endif
 
+#if defined(CONFIG_SMP)
+	z_x86_ipi_setup();
+#endif
+
 	z_cstart();
 }

arch/x86/include/intel64/kernel_arch_func.h

@@ -10,6 +10,14 @@
 
 extern void z_arch_switch(void *switch_to, void **switched_from);
 
+/**
+ * @brief Initialize scheduler IPI vector.
+ *
+ * Called in early BSP boot to set up scheduler IPI handling.
+ */
+
+extern void z_x86_ipi_setup(void);
+
 static inline void z_arch_kernel_init(void)
 {
 	/* nothing */;
@@ -26,6 +34,23 @@ static inline struct _cpu *z_arch_curr_cpu(void)
 	return cpu;
 }
 
+#if defined(CONFIG_SMP) && defined(CONFIG_SCHED_IPI_SUPPORTED)
+
+#include <drivers/interrupt_controller/loapic.h>
+
+/*
+ * it is not clear exactly how/where/why to abstract this, as it
+ * assumes the use of a local APIC (but there's no other mechanism).
+ */
+
+static inline void z_arch_sched_ipi(void)
+{
+	z_loapic_ipi(0, LOAPIC_ICR_IPI_OTHERS, CONFIG_SCHED_IPI_VECTOR);
+}
+
+#endif
+
+
 #endif /* _ASMLANGUAGE */
 
 #endif /* ZEPHYR_ARCH_X86_INCLUDE_INTEL64_KERNEL_ARCH_FUNC_H_ */