[Qemu-devel] [PATCH 02/10] target/ppc: Don't clobber MSR:EE on PM instructions

["Cédric Le Goater" <clg@kaod.org>]

From: Benjamin Herrenschmidt <benh@kernel.crashing.org>

When issuing a power management instruction, we set MSR:EE
to force ppc_hw_interrupt() into calling powerpc_excp()
to deal with the fact that on P7 and P8, the system reset
caused by the wakeup needs to be generated regardless of
the MSR:EE value (using LPCR only).

This however means that the OS will see a bogus SRR1:EE
value which is a problem. It also prevents properly
implementing P9 STOP "light".

So fix this by instead putting some logic in ppc_hw_interrupt()
to decide whether to deliver or not by taking into account the
fact that we are waking up from sleep.

The LPCR isn't checked as this is done in the has_work() test.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
---
 target/ppc/excp_helper.c | 27 +++++++++++++++------------
 1 file changed, 15 insertions(+), 12 deletions(-)

diff --git a/target/ppc/excp_helper.c b/target/ppc/excp_helper.c
index 8407e0ade938..7c7c8d1b9dc6 100644
--- a/target/ppc/excp_helper.c
+++ b/target/ppc/excp_helper.c
@@ -748,6 +748,7 @@ void ppc_cpu_do_interrupt(CPUState *cs)
 static void ppc_hw_interrupt(CPUPPCState *env)
 {
     PowerPCCPU *cpu = ppc_env_get_cpu(env);
+    bool async_deliver;
 
     /* External reset */
     if (env->pending_interrupts & (1 << PPC_INTERRUPT_RESET)) {
@@ -769,11 +770,20 @@ static void ppc_hw_interrupt(CPUPPCState *env)
         return;
     }
 #endif
+
+    /*
+     * For interrupts that gate on MSR:EE, we need to do something a
+     * bit more subtle, as we need to let them through even when EE is
+     * clear when coming out of some power management states (in order
+     * for them to become a 0x100).
+     */
+    async_deliver = (msr_ee != 0) || env->in_pm_state;
+
     /* Hypervisor decrementer exception */
     if (env->pending_interrupts & (1 << PPC_INTERRUPT_HDECR)) {
         /* LPCR will be clear when not supported so this will work */
         bool hdice = !!(env->spr[SPR_LPCR] & LPCR_HDICE);
-        if ((msr_ee != 0 || msr_hv == 0) && hdice) {
+        if ((async_deliver || msr_hv == 0) && hdice) {
             /* HDEC clears on delivery */
             env->pending_interrupts &= ~(1 << PPC_INTERRUPT_HDECR);
             powerpc_excp(cpu, env->excp_model, POWERPC_EXCP_HDECR);
@@ -783,7 +793,7 @@ static void ppc_hw_interrupt(CPUPPCState *env)
     /* Extermal interrupt can ignore MSR:EE under some circumstances */
     if (env->pending_interrupts & (1 << PPC_INTERRUPT_EXT)) {
         bool lpes0 = !!(env->spr[SPR_LPCR] & LPCR_LPES0);
-        if (msr_ee != 0 || (env->has_hv_mode && msr_hv == 0 && !lpes0)) {
+        if (async_deliver || (env->has_hv_mode && msr_hv == 0 && !lpes0)) {
             powerpc_excp(cpu, env->excp_model, POWERPC_EXCP_EXTERNAL);
             return;
         }
@@ -795,7 +805,7 @@ static void ppc_hw_interrupt(CPUPPCState *env)
             return;
         }
     }
-    if (msr_ee != 0) {
+    if (async_deliver != 0) {
         /* Watchdog timer on embedded PowerPC */
         if (env->pending_interrupts & (1 << PPC_INTERRUPT_WDT)) {
             env->pending_interrupts &= ~(1 << PPC_INTERRUPT_WDT);
@@ -943,21 +953,14 @@ void helper_pminsn(CPUPPCState *env, powerpc_pm_insn_t insn)
 
     cs = CPU(ppc_env_get_cpu(env));
     cs->halted = 1;
-    env->in_pm_state = true;
 
     /* The architecture specifies that HDEC interrupts are
      * discarded in PM states
      */
     env->pending_interrupts &= ~(1 << PPC_INTERRUPT_HDECR);
 
-    /* Technically, nap doesn't set EE, but if we don't set it
-     * then ppc_hw_interrupt() won't deliver. We could add some
-     * other tests there based on LPCR but it's simpler to just
-     * whack EE in. It will be cleared by the 0x100 at wakeup
-     * anyway. It will still be observable by the guest in SRR1
-     * but this doesn't seem to be a problem.
-     */
-    env->msr |= (1ull << MSR_EE);
+    /* Condition for waking up at 0x100 */
+    env->in_pm_state = true;
 }
 #endif /* defined(TARGET_PPC64) */
 
-- 
2.20.1