Re: [PATCH v2 7/8] ppc/spapr: Implement FWNMI System Reset delivery

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

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On Tue, Mar 17, 2020 at 12:26:12AM +1000, Nicholas Piggin wrote:
> PAPR requires that if "ibm,nmi-register" succeeds, then the hypervisor
> delivers all system reset and machine check exceptions to the registered
> addresses.
> 
> System Resets are delivered with registers set to the architected state,
> and with no interlock.
> 
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>

Applied to ppc-for-5.0.

> ---
>  hw/ppc/spapr.c | 46 ++++++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 44 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 25221d843c..78e649f47d 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -967,7 +967,29 @@ static void spapr_dt_rtas(SpaprMachineState *spapr, void *fdt)
>      _FDT(fdt_setprop(fdt, rtas, "ibm,max-associativity-domains",
>                       maxdomains, sizeof(maxdomains)));
>  
> -    _FDT(fdt_setprop_cell(fdt, rtas, "rtas-size", RTAS_SIZE));
> +    /*
> +     * FWNMI reserves RTAS_ERROR_LOG_MAX for the machine check error log,
> +     * and 16 bytes per CPU for system reset error log plus an extra 8 bytes.
> +     *
> +     * The system reset requirements are driven by existing Linux and PowerVM
> +     * implementation which (contrary to PAPR) saves r3 in the error log
> +     * structure like machine check, so Linux expects to find the saved r3
> +     * value at the address in r3 upon FWNMI-enabled sreset interrupt (and
> +     * does not look at the error value).
> +     *
> +     * System reset interrupts are not subject to interlock like machine
> +     * check, so this memory area could be corrupted if the sreset is
> +     * interrupted by a machine check (or vice versa) if it was shared. To
> +     * prevent this, system reset uses per-CPU areas for the sreset save
> +     * area. A system reset that interrupts a system reset handler could
> +     * still overwrite this area, but Linux doesn't try to recover in that
> +     * case anyway.
> +     *
> +     * The extra 8 bytes is required because Linux's FWNMI error log check
> +     * is off-by-one.
> +     */
> +    _FDT(fdt_setprop_cell(fdt, rtas, "rtas-size", RTAS_ERROR_LOG_MAX +
> +			  ms->smp.max_cpus * sizeof(uint64_t)*2 + sizeof(uint64_t)));
>      _FDT(fdt_setprop_cell(fdt, rtas, "rtas-error-log-max",
>                            RTAS_ERROR_LOG_MAX));
>      _FDT(fdt_setprop_cell(fdt, rtas, "rtas-event-scan-rate",
> @@ -3399,8 +3421,28 @@ static void spapr_machine_finalizefn(Object *obj)
>  
>  void spapr_do_system_reset_on_cpu(CPUState *cs, run_on_cpu_data arg)
>  {
> +    SpaprMachineState *spapr = SPAPR_MACHINE(qdev_get_machine());
> +
>      cpu_synchronize_state(cs);
> -    ppc_cpu_do_system_reset(cs, -1);
> +    /* If FWNMI is inactive, addr will be -1, which will deliver to 0x100 */
> +    if (spapr->fwnmi_system_reset_addr != -1) {
> +        uint64_t rtas_addr, addr;
> +        PowerPCCPU *cpu = POWERPC_CPU(cs);
> +        CPUPPCState *env = &cpu->env;
> +
> +        /* get rtas addr from fdt */
> +        rtas_addr = spapr_get_rtas_addr();
> +        if (!rtas_addr) {
> +            qemu_system_guest_panicked(NULL);
> +            return;
> +        }
> +
> +        addr = rtas_addr + RTAS_ERROR_LOG_MAX + cs->cpu_index * sizeof(uint64_t)*2;
> +        stq_be_phys(&address_space_memory, addr, env->gpr[3]);
> +        stq_be_phys(&address_space_memory, addr + sizeof(uint64_t), 0);
> +        env->gpr[3] = addr;
> +    }
> +    ppc_cpu_do_system_reset(cs, spapr->fwnmi_system_reset_addr);
>  }
>  
>  static void spapr_nmi(NMIState *n, int cpu_index, Error **errp)

-- 
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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