Re: [Qemu-ppc] [PATCH v7 3/6] target/ppc: Handle NMI guest exit

[David Gibson]

On Fri, Mar 22, 2019 at 12:03:58PM +0530, Aravinda Prasad wrote:
> Memory error such as bit flips that cannot be corrected
> by hardware are passed on to the kernel for handling.
> If the memory address in error belongs to guest then
> the guest kernel is responsible for taking suitable action.
> Patch [1] enhances KVM to exit guest with exit reason
> set to KVM_EXIT_NMI in such cases. This patch handles
> KVM_EXIT_NMI exit.
> 
> [1] https://www.spinics.net/lists/kvm-ppc/msg12637.html
>     (e20bbd3d and related commits)
> 
> Signed-off-by: Aravinda Prasad <address@hidden>
> ---
>  hw/ppc/spapr_events.c  |   22 ++++++++++++++++++++++
>  include/hw/ppc/spapr.h |    1 +
>  target/ppc/kvm.c       |   16 ++++++++++++++++
>  target/ppc/kvm_ppc.h   |    2 ++
>  4 files changed, 41 insertions(+)
> 
> diff --git a/hw/ppc/spapr_events.c b/hw/ppc/spapr_events.c
> index ae0f093..e7a24ad 100644
> --- a/hw/ppc/spapr_events.c
> +++ b/hw/ppc/spapr_events.c
> @@ -620,6 +620,28 @@ void 
> spapr_hotplug_req_remove_by_count_indexed(SpaprDrcType drc_type,
>                              RTAS_LOG_V6_HP_ACTION_REMOVE, drc_type, &drc_id);
>  }
>  
> +void spapr_mce_req_event(PowerPCCPU *cpu, bool recovered)
> +{
> +    SpaprMachineState *spapr = SPAPR_MACHINE(qdev_get_machine());
> +
> +    while (spapr->mc_status != -1) {
> +        /*
> +         * Check whether the same CPU got machine check error
> +         * while still handling the mc error (i.e., before
> +         * that CPU called "ibm,nmi-interlock"
> +         */
> +        if (spapr->mc_status == cpu->vcpu_id) {
> +            qemu_system_guest_panicked(NULL);
> +        }
> +        qemu_cond_wait_iothread(&spapr->mc_delivery_cond);
> +        /* If the system is reset meanwhile, then just return */
> +        if (spapr->mc_reset) {

I don't really see what this accomplishes.  IIUC mc_reset is true from
reset time until nmi-register is called.  Which means you could just
check for guest_mnachine_check_addre being unset - in which case don't
you need to fallback to the old machine check behaviour anyway?

> +            return;
> +        }
> +    }
> +    spapr->mc_status = cpu->vcpu_id;
> +}
> +
>  static void check_exception(PowerPCCPU *cpu, SpaprMachineState *spapr,
>                              uint32_t token, uint32_t nargs,
>                              target_ulong args,
> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> index ee5589d..b0d8c18 100644
> --- a/include/hw/ppc/spapr.h
> +++ b/include/hw/ppc/spapr.h
> @@ -792,6 +792,7 @@ void spapr_reallocate_hpt(SpaprMachineState *spapr, int 
> shift,
>                            Error **errp);
>  void spapr_clear_pending_events(SpaprMachineState *spapr);
>  int spapr_max_server_number(SpaprMachineState *spapr);
> +void spapr_mce_req_event(PowerPCCPU *cpu, bool recovered);
>  
>  /* DRC callbacks. */
>  void spapr_core_release(DeviceState *dev);
> diff --git a/target/ppc/kvm.c b/target/ppc/kvm.c
> index 2427c8e..a593448 100644
> --- a/target/ppc/kvm.c
> +++ b/target/ppc/kvm.c
> @@ -1738,6 +1738,11 @@ int kvm_arch_handle_exit(CPUState *cs, struct kvm_run 
> *run)
>          ret = 0;
>          break;
>  
> +    case KVM_EXIT_NMI:
> +        DPRINTF("handle NMI exception\n");

tracepoints are generally preferred to new DPRINTFs.

> +        ret = kvm_handle_nmi(cpu, run);
> +        break;
> +
>      default:
>          fprintf(stderr, "KVM: unknown exit reason %d\n", run->exit_reason);
>          ret = -1;
> @@ -2803,6 +2808,17 @@ int kvm_arch_msi_data_to_gsi(uint32_t data)
>      return data & 0xffff;
>  }
>  
> +int kvm_handle_nmi(PowerPCCPU *cpu, struct kvm_run *run)
> +{
> +    bool recovered = run->flags & KVM_RUN_PPC_NMI_DISP_FULLY_RECOV;
> +
> +    cpu_synchronize_state(CPU(cpu));
> +
> +    spapr_mce_req_event(cpu, recovered);
> +
> +    return 0;
> +}
> +
>  int kvmppc_enable_hwrng(void)
>  {
>      if (!kvm_enabled() || !kvm_check_extension(kvm_state, 
> KVM_CAP_PPC_HWRNG)) {
> diff --git a/target/ppc/kvm_ppc.h b/target/ppc/kvm_ppc.h
> index 2c2ea30..df5e85f 100644
> --- a/target/ppc/kvm_ppc.h
> +++ b/target/ppc/kvm_ppc.h
> @@ -80,6 +80,8 @@ bool kvmppc_hpt_needs_host_contiguous_pages(void);
>  void kvm_check_mmu(PowerPCCPU *cpu, Error **errp);
>  void kvmppc_set_reg_ppc_online(PowerPCCPU *cpu, unsigned int online);
>  
> +int kvm_handle_nmi(PowerPCCPU *cpu, struct kvm_run *run);
> +
>  #else
>  
>  static inline uint32_t kvmppc_get_tbfreq(void)
> 

-- 
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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