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

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

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On Wed, Apr 24, 2019 at 10:20:42AM +0530, Aravinda Prasad wrote:
65;5601;1c> 
> 
> On Tuesday 23 April 2019 12:23 PM, David Gibson wrote:
> > On Mon, Apr 22, 2019 at 12:33:16PM +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 <aravinda@linux.vnet.ibm.com>
> > 
> > LGTM, apart from one detail noted below.
> > 
> >> ---
> >>  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),
> > 
> > So, technically this is a breaking change to the migration stream.  If
> > this is applied immediately after the earlier patch introducing the
> > subsection it would be ok in practice, but it would still be
> > preferable to make all the migration stream changes together.
> 
> Do you mean that all .fields entries to vmstate_spapr_machine_check
> should be in a single patch?

Yes, that's preferable.  If necessary you can move the migration
support out into its own patch which goes after the implementation of
the underlying state.

> 
> Because this patch introduced the variable mc_status, I added it to
> vmstate_spapr_machine_check.
> 
> Regards,
> Aravinda
> 
> > 
> >>          VMSTATE_END_OF_LIST()
> >>      },
> >>  };
> >> @@ -3085,6 +3087,7 @@ static void spapr_machine_init(MachineState *machine)
> >>          kvmppc_spapr_enable_inkernel_multitce();
> >>      }
> >>  
> >> +    spapr->mc_status = -1;
> >>      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"
> >> +         */
> >> +        if (spapr->mc_status == cpu->vcpu_id) {
> >> +            qemu_system_guest_panicked(NULL);
> >> +        }
> >> +        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"
> >> +
> >>
> > 
> 

-- 
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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