Re: [Qemu-devel] [PATCH 3/4] spapr: Handle "ibm, nmi-register" and "ibm, nmi-interlock" RTAS calls

[Thomas Huth <thuth@redhat.com>]

On 11/11/15 18:15, Aravinda Prasad wrote:
> This patch adds support in QEMU to handle "ibm,nmi-register"
> and "ibm,nmi-interlock" RTAS calls.
> 
> The machine check notification address is saved when the
> OS issues "ibm,nmi-register" RTAS call.
> 
> This patch also handles the case when multiple processors
> experience machine check at or about the same time by
> handling "ibm,nmi-interlock" call. In such cases, as per
> PAPR, subsequent processors serialize waiting for the first
> processor to issue the "ibm,nmi-interlock" call. The second
> processor waits till the first processor, which also
> received a machine check error, is done reading the error
> log. The first processor issues "ibm,nmi-interlock" call
> when the error log is consumed. This patch implements the
> releasing part of the error-log while subsequent patch
> (which builds error log) handles the locking part.
> 
> Signed-off-by: Aravinda Prasad <aravinda@linux.vnet.ibm.com>
> ---
>  hw/ppc/spapr_rtas.c    |   29 +++++++++++++++++++++++++++++
>  include/hw/ppc/spapr.h |    8 +++++++-
>  2 files changed, 36 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/ppc/spapr_rtas.c b/hw/ppc/spapr_rtas.c
> index 9869bc9..fd4d2af 100644
> --- a/hw/ppc/spapr_rtas.c
> +++ b/hw/ppc/spapr_rtas.c
> @@ -597,6 +597,31 @@ out:
>      rtas_st(rets, 0, rc);
>  }
>  
> +static void rtas_ibm_nmi_register(PowerPCCPU *cpu,
> +                                  sPAPRMachineState *spapr,
> +                                  uint32_t token, uint32_t nargs,
> +                                  target_ulong args,
> +                                  uint32_t nret, target_ulong rets)
> +{
> +    qemu_mutex_init(&spapr->mc_in_progress);
> +    spapr->guest_machine_check_addr = rtas_ld(args, 1);
> +    rtas_st(rets, 0, RTAS_OUT_SUCCESS);
> +}
> +
> +static void rtas_ibm_nmi_interlock(PowerPCCPU *cpu,
> +                                   sPAPRMachineState *spapr,
> +                                   uint32_t token, uint32_t nargs,
> +                                   target_ulong args,
> +                                   uint32_t nret, target_ulong rets)
> +{
> +    /*
> +     * VCPU issuing "ibm,nmi-interlock" is done with NMI handling,
> +     * hence unlock mc_in_progress.
> +     */
> +    qemu_mutex_unlock(&spapr->mc_in_progress);
> +    rtas_st(rets, 0, RTAS_OUT_SUCCESS);
> +}

Maybe the interlock function should return an error if the nmi_register
function has not been called before? OTOH, RTAS is not supposed to do
excessive parameter checking, so this is maybe not worth the effort.

 Thomas