x86/S3: add cache flush on secondary CPUs before going to sleep

Secondary CPUs, between doing their final memory writes (particularly
updating cpu_initialized) and getting a subsequent INIT, may not write
back all modified data. The INIT itself then causes those modifications
to be lost, so in the cpu_initialized case the CPU would find itself
already initialized, (intentionally) entering an infinite loop instead
of actually coming online.

Signed-off-by: Ben Guthro <ben@xxxxxxxxxx>

Make acpi_dead_idle() call default_dead_idle() rather than duplicating
the logic there.

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

--- a/xen/arch/x86/acpi/cpu_idle.c
+++ b/xen/arch/x86/acpi/cpu_idle.c
@@ -659,8 +659,7 @@ void acpi_dead_idle(void)
     }
 
 default_halt:
-    for ( ; ; )
-        halt();
+    default_dead_idle();
 }
 
 int cpuidle_init_cpu(unsigned int cpu)
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -45,6 +45,7 @@
 #include <asm/desc.h>
 #include <asm/i387.h>
 #include <asm/xstate.h>
+#include <asm/cpuidle.h>
 #include <asm/mpspec.h>
 #include <asm/ldt.h>
 #include <asm/fixmap.h>
@@ -64,7 +65,6 @@ DEFINE_PER_CPU(struct vcpu *, curr_vcpu)
 DEFINE_PER_CPU(unsigned long, cr4);
 
 static void default_idle(void);
-static void default_dead_idle(void);
 void (*pm_idle) (void) __read_mostly = default_idle;
 void (*dead_idle) (void) __read_mostly = default_dead_idle;
 
@@ -82,8 +82,9 @@ static void default_idle(void)
         local_irq_enable();
 }
 
-static void default_dead_idle(void)
+void default_dead_idle(void)
 {
+    wbinvd();
     for ( ; ; )
         halt();
 }
--- a/xen/include/asm-x86/cpuidle.h
+++ b/xen/include/asm-x86/cpuidle.h
@@ -18,6 +18,7 @@ extern uint64_t (*cpuidle_get_tick)(void
 
 int mwait_idle_init(struct notifier_block *);
 int cpuidle_init_cpu(unsigned int cpu);
+void default_dead_idle(void);
 void acpi_dead_idle(void);
 void trace_exit_reason(u32 *irq_traced);
 void update_idle_stats(struct acpi_processor_power *,