Re: [Qemu-devel] [Qemu-ppc] [PATCH v8 3/6] target/ppc: Handle NMI guest exit

[Greg Kurz <groug@kaod.org>]

On Mon, 22 Apr 2019 12:33:16 +0530
Aravinda Prasad <aravinda@linux.vnet.ibm.com> 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 <aravinda@linux.vnet.ibm.com>
> ---
>  hw/ppc/spapr.c          |    3 +++
>  hw/ppc/spapr_events.c   |   22 ++++++++++++++++++++++
>  hw/ppc/spapr_rtas.c     |    5 +++++
>  include/hw/ppc/spapr.h  |    6 ++++++
>  target/ppc/kvm.c        |   16 ++++++++++++++++
>  target/ppc/kvm_ppc.h    |    2 ++
>  target/ppc/trace-events |    2 ++
>  7 files changed, 56 insertions(+)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 6642cb5..2779efe 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -1806,6 +1806,7 @@ static void spapr_machine_reset(void)
>  
>      spapr->cas_reboot = false;
>  
> +    spapr->mc_status = -1;
>      spapr->guest_machine_check_addr = -1;
>  
>      /* Signal all vCPUs waiting on this condition */
> @@ -2106,6 +2107,7 @@ static const VMStateDescription vmstate_spapr_machine_check = {
>      .minimum_version_id = 1,
>      .fields = (VMStateField[]) {
>          VMSTATE_UINT64(guest_machine_check_addr, SpaprMachineState),
> +        VMSTATE_INT32(mc_status, SpaprMachineState),
>          VMSTATE_END_OF_LIST()
>      },
>  };
> @@ -3085,6 +3087,7 @@ static void spapr_machine_init(MachineState *machine)
>          kvmppc_spapr_enable_inkernel_multitce();
>      }
>  
> +    spapr->mc_status = -1;

Since this is done at reset, do we need it here ?

>      qemu_cond_init(&spapr->mc_delivery_cond);
>  }
>  
> diff --git a/hw/ppc/spapr_events.c b/hw/ppc/spapr_events.c
> index ae0f093..9922a23 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"

Missing )

> +         */
> +        if (spapr->mc_status == cpu->vcpu_id) {
> +            qemu_system_guest_panicked(NULL);

If we don't also return, is there a chance we end up stuck in
qemu_cond_wait_iothread() below ?

> +        }
> +        qemu_cond_wait_iothread(&spapr->mc_delivery_cond);
> +        /* Meanwhile if the system is reset, then just return */
> +        if (spapr->guest_machine_check_addr == -1) {
> +            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/hw/ppc/spapr_rtas.c b/hw/ppc/spapr_rtas.c
> index c2f3991..d3499f9 100644
> --- a/hw/ppc/spapr_rtas.c
> +++ b/hw/ppc/spapr_rtas.c
> @@ -375,6 +375,11 @@ static void rtas_ibm_nmi_interlock(PowerPCCPU *cpu,
>          /* NMI register not called */
>          rtas_st(rets, 0, RTAS_OUT_PARAM_ERROR);
>      } else {
> +        /*
> +         * vCPU issuing "ibm,nmi-interlock" is done with NMI handling,
> +         * hence unset mc_status.
> +         */
> +        spapr->mc_status = -1;
>          qemu_cond_signal(&spapr->mc_delivery_cond);
>          rtas_st(rets, 0, RTAS_OUT_SUCCESS);
>      }
> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> index ec6f33e..f7204d0 100644
> --- a/include/hw/ppc/spapr.h
> +++ b/include/hw/ppc/spapr.h
> @@ -189,6 +189,11 @@ struct SpaprMachineState {
>  
>      /* State related to "ibm,nmi-register" and "ibm,nmi-interlock" calls */
>      target_ulong guest_machine_check_addr;
> +    /*
> +     * mc_status is set to -1 if mc is not in progress, else is set to the CPU
> +     * handling the mc.
> +     */
> +    int mc_status;
>      QemuCond mc_delivery_cond;
>  
>      /*< public >*/
> @@ -792,6 +797,7 @@ void spapr_clear_pending_events(SpaprMachineState *spapr);
>  int spapr_max_server_number(SpaprMachineState *spapr);
>  void spapr_store_hpte(PowerPCCPU *cpu, hwaddr ptex,
>                        uint64_t pte0, uint64_t pte1);
> +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 9e86db0..5eedce8 100644
> --- a/target/ppc/kvm.c
> +++ b/target/ppc/kvm.c
> @@ -1759,6 +1759,11 @@ int kvm_arch_handle_exit(CPUState *cs, struct kvm_run *run)
>          ret = 0;
>          break;
>  
> +    case KVM_EXIT_NMI:
> +        trace_kvm_handle_nmi_exception();
> +        ret = kvm_handle_nmi(cpu, run);
> +        break;
> +
>      default:
>          fprintf(stderr, "KVM: unknown exit reason %d\n", run->exit_reason);
>          ret = -1;
> @@ -2837,6 +2842,17 @@ 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 2238513..6edc42f 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)
> diff --git a/target/ppc/trace-events b/target/ppc/trace-events
> index 7b3cfe1..d5691d2 100644
> --- a/target/ppc/trace-events
> +++ b/target/ppc/trace-events
> @@ -28,3 +28,5 @@ kvm_handle_papr_hcall(void) "handle PAPR hypercall"
>  kvm_handle_epr(void) "handle epr"
>  kvm_handle_watchdog_expiry(void) "handle watchdog expiry"
>  kvm_handle_debug_exception(void) "handle debug exception"
> +kvm_handle_nmi_exception(void) "handle NMI exception"
> +

new blank line at EOF.

> 
>