HDEC is defined to not wake from PM state. There is a check in the HDEC
timer to avoid setting the interrupt if we are in a PM state, but no
check on PM entry to lower HDEC if it already fired. This can cause a
HDECR wake up and  QEMU abort with unsupported exception in Power Save
mode.

Fixes: 4b236b621bf ("ppc: Initial HDEC support")
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 target/ppc/excp_helper.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/target/ppc/excp_helper.c b/target/ppc/excp_helper.c
index 003805b202..9aa8e46566 100644
--- a/target/ppc/excp_helper.c
+++ b/target/ppc/excp_helper.c
@@ -2685,6 +2685,12 @@ void helper_pminsn(CPUPPCState *env, uint32_t insn)
     env->resume_as_sreset = (insn != PPC_PM_STOP) ||
         (env->spr[SPR_PSSCR] & PSSCR_EC);
 
+    /* HDECR is not to wake from PM state, it may have already fired */
+    if (env->resume_as_sreset) {
+        PowerPCCPU *cpu = env_archcpu(env);
+        ppc_set_irq(cpu, PPC_INTERRUPT_HDECR, 0);
+    }
+
     ppc_maybe_interrupt(env);
 }
 #endif /* defined(TARGET_PPC64) */
-- 
2.40.1

On 7/26/23 20:22, Nicholas Piggin wrote:
> HDEC is defined to not wake from PM state. There is a check in the HDEC
> timer to avoid setting the interrupt if we are in a PM state, but no
> check on PM entry to lower HDEC if it already fired. This can cause a
> HDECR wake up and  QEMU abort with unsupported exception in Power Save
> mode.
> 
> Fixes: 4b236b621bf ("ppc: Initial HDEC support")
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>


Reviewed-by: Cédric Le Goater <clg@kaod.org>

Thanks,

C.


> ---
>   target/ppc/excp_helper.c | 6 ++++++
>   1 file changed, 6 insertions(+)
> 
> diff --git a/target/ppc/excp_helper.c b/target/ppc/excp_helper.c
> index 003805b202..9aa8e46566 100644
> --- a/target/ppc/excp_helper.c
> +++ b/target/ppc/excp_helper.c
> @@ -2685,6 +2685,12 @@ void helper_pminsn(CPUPPCState *env, uint32_t insn)
>       env->resume_as_sreset = (insn != PPC_PM_STOP) ||
>           (env->spr[SPR_PSSCR] & PSSCR_EC);
>   
> +    /* HDECR is not to wake from PM state, it may have already fired */
> +    if (env->resume_as_sreset) {
> +        PowerPCCPU *cpu = env_archcpu(env);
> +        ppc_set_irq(cpu, PPC_INTERRUPT_HDECR, 0);
> +    }
> +
>       ppc_maybe_interrupt(env);
>   }
>   #endif /* defined(TARGET_PPC64) */