sparc64: Make sure %pil interrupts are enabled during hypervisor yield.

In arch_cpu_idle() we must enable %pil based interrupts before
potentially invoking the hypervisor cpu yield call.

As per the Hypervisor API documentation for cpu_yield:

	Interrupts which are blocked by some mechanism other that
	pstate.ie (for example %pil) are not guaranteed to cause
	a return from this service.

It seems that only first generation Niagara chips are hit by this
bug.  My best guess is that later chips implement this in hardware
and wake up anyways from %pil events, whereas in first generation
chips the yield is implemented completely in hypervisor code and
requires %pil to be enabled in order to wake properly from this
call.

Fixes: 87fa05aeb3a5 ("sparc: Use generic idle loop")
Reported-by: Fabio M. Di Nitto <fabbione@fabbione.net>
Reported-by: Jan Engelhardt <jengelh@inai.de>
Tested-by: Jan Engelhardt <jengelh@inai.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/arch/sparc/kernel/process_64.c b/arch/sparc/kernel/process_64.c
index 32a280ec38c1d6edef71b5576ce474221726ec1e..d7b4967f8fa6209307854c367347f88d14103839 100644 (file)
--- a/arch/sparc/kernel/process_64.c
+++ b/arch/sparc/kernel/process_64.c
@@ -58,9 +58,12 @@ void arch_cpu_idle(void)
 {
        if (tlb_type != hypervisor) {
                touch_nmi_watchdog();
+               local_irq_enable();
        } else {
                unsigned long pstate;
 
+               local_irq_enable();
+
                 /* The sun4v sleeping code requires that we have PSTATE.IE cleared over
                  * the cpu sleep hypervisor call.
                  */
@@ -82,7 +85,6 @@ void arch_cpu_idle(void)
                        : "=&r" (pstate)
                        : "i" (PSTATE_IE));
        }
-       local_irq_enable();
 }
 
 #ifdef CONFIG_HOTPLUG_CPU