console: adjust IRQ initialization

In order for a Xen internal PCI device driver to enable MSI on the
device, we need another hook which the driver can use to create the IRQ
(doing this in the init_preirq hook is too early, since IRQ code hasn't
got initialized at that time yet, and doing it in init_postirq is too
late because at least on x86 smp_intr_init() needs to know the IRQ
number).

On x86 this additionally requires a slight ordering change to IRQ
initialization, to facilitate calling the new hook between basic
initialization and the call path leading to smp_intr_init().

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/x86/i8259.c
+++ b/xen/arch/x86/i8259.c
@@ -342,8 +342,6 @@ void __init init_IRQ(void)
 
     init_8259A(0);
 
-    BUG_ON(init_irq_data() < 0);
-
     for (irq = 0; platform_legacy_irq(irq); irq++) {
         struct irq_desc *desc = irq_to_desc(irq);
         
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -576,6 +576,7 @@ void __init noreturn __start_xen(unsigne
     unsigned long nr_pages, raw_max_page, modules_headroom, *module_map;
     int i, j, e820_warn = 0, bytes = 0;
     bool_t acpi_boot_table_init_done = 0;
+    int ret;
     struct domain *dom0;
     struct ns16550_defaults ns16550 = {
         .data_bits = 8,
@@ -1281,6 +1282,12 @@ void __init noreturn __start_xen(unsigne
 
     x2apic_bsp_setup();
 
+    ret = init_irq_data();
+    if ( ret < 0 )
+        panic("Error %d setting up IRQ data\n", ret);
+
+    console_init_irq();
+
     init_IRQ();
 
     module_map = xmalloc_array(unsigned long, BITS_TO_LONGS(mbi->mods_count));
@@ -1366,7 +1373,7 @@ void __init noreturn __start_xen(unsigne
 
         if ( (num_online_cpus() < max_cpus) && !cpu_online(i) )
         {
-            int ret = cpu_up(i);
+            ret = cpu_up(i);
             if ( ret != 0 )
                 printk("Failed to bring up CPU %u (error %d)\n", i, ret);
         }
--- a/xen/drivers/char/console.c
+++ b/xen/drivers/char/console.c
@@ -771,6 +771,11 @@ void __init console_init_ring(void)
     printk("Allocated console ring of %u KiB.\n", opt_conring_size >> 10);
 }
 
+void __init console_init_irq(void)
+{
+    serial_init_irq();
+}
+
 void __init console_init_postirq(void)
 {
     serial_init_postirq();
--- a/xen/drivers/char/serial.c
+++ b/xen/drivers/char/serial.c
@@ -504,6 +504,15 @@ void __init serial_init_preirq(void)
             com[i].driver->init_preirq(&com[i]);
 }
 
+void __init serial_init_irq(void)
+{
+    unsigned int i;
+
+    for ( i = 0; i < ARRAY_SIZE(com); i++ )
+        if ( com[i].driver && com[i].driver->init_irq )
+            com[i].driver->init_irq(&com[i]);
+}
+
 void __init serial_init_postirq(void)
 {
     int i;
--- a/xen/include/xen/console.h
+++ b/xen/include/xen/console.h
@@ -15,6 +15,7 @@ int console_loglvl_op(struct xen_sysctl_
 
 void console_init_preirq(void);
 void console_init_ring(void);
+void console_init_irq(void);
 void console_init_postirq(void);
 void console_endboot(void);
 int console_has(const char *device);
--- a/xen/include/xen/serial.h
+++ b/xen/include/xen/serial.h
@@ -64,6 +64,7 @@ struct serial_port {
 struct uart_driver {
     /* Driver initialisation (pre- and post-IRQ subsystem setup). */
     void (*init_preirq)(struct serial_port *);
+    void (*init_irq)(struct serial_port *);
     void (*init_postirq)(struct serial_port *);
     /* Hook to clean up after Xen bootstrap (before domain 0 runs). */
     void (*endboot)(struct serial_port *);
@@ -99,8 +100,9 @@ struct uart_driver {
 #define SERHND_LO       (1<<3) /* Ditto, except that the MSB is cleared.  */
 #define SERHND_COOKED   (1<<4) /* Newline/carriage-return translation?    */
 
-/* Two-stage initialisation (before/after IRQ-subsystem initialisation). */
+/* Three-stage initialisation (before/during/after IRQ-subsystem setup). */
 void serial_init_preirq(void);
+void serial_init_irq(void);
 void serial_init_postirq(void);
 
 /* Clean-up hook before domain 0 runs. */