Re: [PATCH 1/4] target/ppc: Fix non-maskable interrupt while halted

[Miles Glenn]

Reviewed-by: Glenn Miles <milesg@linux.ibm.com>

On Mon, 2024-11-25 at 23:20 +1000, Nicholas Piggin wrote:
> The ppc (pnv and spapr) NMI injection code does not go through the
> asynchronous interrupt path and set a bit in env->pending_interrupts
> and raise an interrupt request that the cpu_exec() loop can see.
> Instead it injects the exception directly into registers.
> 
> This can lead to cpu_exec() missing that the thread has work to do,
> if a NMI is injected while it was idle.
> 
> Fix this by clearing halted when injecting the interrupt. Probably
> NMI injection should be reworked to use the interrupt request
> interface,
> but this seems to work as a minimal fix.
> 
> Fixes: 3431648272d3 ("spapr: Add support for new NMI interface")
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
> ---
>  target/ppc/excp_helper.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/target/ppc/excp_helper.c b/target/ppc/excp_helper.c
> index 70daa5076a..9f811af0a4 100644
> --- a/target/ppc/excp_helper.c
> +++ b/target/ppc/excp_helper.c
> @@ -2495,10 +2495,16 @@ static void ppc_deliver_interrupt(CPUPPCState
> *env, int interrupt)
>      }
>  }
>  
> +/*
> + * system reset is not delivered via normal irq method, so have to
> set
> + * halted = 0 to resume CPU running if it was halted. Possibly we
> should
> + * move it over to using PPC_INTERRUPT_RESET rather than
> async_run_on_cpu.
> + */
>  void ppc_cpu_do_system_reset(CPUState *cs)
>  {
>      PowerPCCPU *cpu = POWERPC_CPU(cs);
>  
> +    cs->halted = 0;
>      powerpc_excp(cpu, POWERPC_EXCP_RESET);
>  }
>  
> @@ -2520,6 +2526,7 @@ void ppc_cpu_do_fwnmi_machine_check(CPUState
> *cs, target_ulong vector)
>  
>      /* Anything for nested required here? MSR[HV] bit? */
>  
> +    cs->halted = 0;
>      powerpc_set_excp_state(cpu, vector, msr);
>  }
>