Re: [PATCH v2 8/8] ppc/spapr: Ignore common "ibm,nmi-interlock" Linux bug

[David Gibson <david@gibson.dropbear.id.au>]

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On Tue, Mar 17, 2020 at 12:26:13AM +1000, Nicholas Piggin wrote:
> Linux kernels call "ibm,nmi-interlock" in their system reset handlers
> contrary to PAPR. Returning an error because the CPU does not hold the
> interlock here causes Linux to print warning messages. PowerVM returns
> success in this case, so do the same for now.
> 
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>

Applied, thanks.

> ---
>  hw/ppc/spapr_rtas.c | 14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/ppc/spapr_rtas.c b/hw/ppc/spapr_rtas.c
> index 521e6b0b72..9fb8c8632a 100644
> --- a/hw/ppc/spapr_rtas.c
> +++ b/hw/ppc/spapr_rtas.c
> @@ -461,8 +461,18 @@ static void rtas_ibm_nmi_interlock(PowerPCCPU *cpu,
>      }
>  
>      if (spapr->fwnmi_machine_check_interlock != cpu->vcpu_id) {
> -        /* The vCPU that hit the NMI should invoke "ibm,nmi-interlock" */
> -        rtas_st(rets, 0, RTAS_OUT_PARAM_ERROR);
> +        /*
> +	 * The vCPU that hit the NMI should invoke "ibm,nmi-interlock"
> +         * This should be PARAM_ERROR, but Linux calls "ibm,nmi-interlock"
> +	 * for system reset interrupts, despite them not being interlocked.
> +	 * PowerVM silently ignores this and returns success here. Returning
> +	 * failure causes Linux to print the error "FWNMI: nmi-interlock
> +	 * failed: -3", although no other apparent ill effects, this is a
> +	 * regression for the user when enabling FWNMI. So for now, match
> +	 * PowerVM. When most Linux clients are fixed, this could be
> +	 * changed.
> +	 */
> +        rtas_st(rets, 0, RTAS_OUT_SUCCESS);
>          return;
>      }
>  

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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