On Mon, Apr 22, 2019 at 12:33:35PM +0530, Aravinda Prasad wrote:
> Enable the KVM capability KVM_CAP_PPC_FWNMI so that
> the KVM causes guest exit with NMI as exit reason
> when it encounters a machine check exception on the
> address belonging to a guest. Without this capability
> enabled, KVM redirects machine check exceptions to
> guest's 0x200 vector.
> 
> This patch also deals with the case when a guest with
> the KVM_CAP_PPC_FWNMI capability enabled is attempted
> to migrate to a host that does not support this
> capability.
> 
> Signed-off-by: Aravinda Prasad <aravinda@linux.vnet.ibm.com>
> ---
>  hw/ppc/spapr.c         |    1 +
>  hw/ppc/spapr_caps.c    |   26 ++++++++++++++++++++++++++
>  hw/ppc/spapr_rtas.c    |   14 ++++++++++++++
>  include/hw/ppc/spapr.h |    4 +++-
>  target/ppc/kvm.c       |   14 ++++++++++++++
>  target/ppc/kvm_ppc.h   |    6 ++++++
>  6 files changed, 64 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index ffd1715..44e09bb 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -4372,6 +4372,7 @@ static void spapr_machine_class_init(ObjectClass *oc, void *data)
>      smc->default_caps.caps[SPAPR_CAP_NESTED_KVM_HV] = SPAPR_CAP_OFF;
>      smc->default_caps.caps[SPAPR_CAP_LARGE_DECREMENTER] = SPAPR_CAP_ON;
>      smc->default_caps.caps[SPAPR_CAP_CCF_ASSIST] = SPAPR_CAP_OFF;
> +    smc->default_caps.caps[SPAPR_CAP_FWNMI_MCE] = SPAPR_CAP_OFF;
>      spapr_caps_add_properties(smc, &error_abort);
>      smc->irq = &spapr_irq_xics;
>      smc->dr_phb_enabled = true;
> diff --git a/hw/ppc/spapr_caps.c b/hw/ppc/spapr_caps.c
> index edc5ed0..5b3af04 100644
> --- a/hw/ppc/spapr_caps.c
> +++ b/hw/ppc/spapr_caps.c
> @@ -473,6 +473,22 @@ static void cap_ccf_assist_apply(SpaprMachineState *spapr, uint8_t val,
>      }
>  }
>  
> +static void cap_fwnmi_mce_apply(SpaprMachineState *spapr, uint8_t val,
> +                                Error **errp)
> +{
> +    PowerPCCPU *cpu = POWERPC_CPU(first_cpu);
> +
> +    if (!val) {
> +        return; /* Disabled by default */
> +    }
> +
> +    if (kvm_enabled()) {
> +        if (kvmppc_fwnmi_enable(cpu)) {
> +            error_setg(errp, "Requested fwnmi capability not support by KVM");
> +        }
> +    }
> +}
> +
>  SpaprCapabilityInfo capability_table[SPAPR_CAP_NUM] = {
>      [SPAPR_CAP_HTM] = {
>          .name = "htm",
> @@ -571,6 +587,15 @@ SpaprCapabilityInfo capability_table[SPAPR_CAP_NUM] = {
>          .type = "bool",
>          .apply = cap_ccf_assist_apply,
>      },
> +    [SPAPR_CAP_FWNMI_MCE] = {
> +        .name = "fwnmi-mce",
> +        .description = "Handle fwnmi machine check exceptions",
> +        .index = SPAPR_CAP_FWNMI_MCE,
> +        .get = spapr_cap_get_bool,
> +        .set = spapr_cap_set_bool,
> +        .type = "bool",
> +        .apply = cap_fwnmi_mce_apply,
> +    },
>  };
>  
>  static SpaprCapabilities default_caps_with_cpu(SpaprMachineState *spapr,
> @@ -706,6 +731,7 @@ SPAPR_CAP_MIG_STATE(ibs, SPAPR_CAP_IBS);
>  SPAPR_CAP_MIG_STATE(nested_kvm_hv, SPAPR_CAP_NESTED_KVM_HV);
>  SPAPR_CAP_MIG_STATE(large_decr, SPAPR_CAP_LARGE_DECREMENTER);
>  SPAPR_CAP_MIG_STATE(ccf_assist, SPAPR_CAP_CCF_ASSIST);
> +SPAPR_CAP_MIG_STATE(fwnmi, SPAPR_CAP_FWNMI_MCE);
>  
>  void spapr_caps_init(SpaprMachineState *spapr)
>  {
> diff --git a/hw/ppc/spapr_rtas.c b/hw/ppc/spapr_rtas.c
> index d3499f9..997cf19 100644
> --- a/hw/ppc/spapr_rtas.c
> +++ b/hw/ppc/spapr_rtas.c
> @@ -49,6 +49,7 @@
>  #include "hw/ppc/fdt.h"
>  #include "target/ppc/mmu-hash64.h"
>  #include "target/ppc/mmu-book3s-v3.h"
> +#include "kvm_ppc.h"
>  
>  static void rtas_display_character(PowerPCCPU *cpu, SpaprMachineState *spapr,
>                                     uint32_t token, uint32_t nargs,
> @@ -354,6 +355,7 @@ static void rtas_ibm_nmi_register(PowerPCCPU *cpu,
>                                    target_ulong args,
>                                    uint32_t nret, target_ulong rets)
>  {
> +    int ret;
>      uint64_t rtas_addr = spapr_get_rtas_addr();
>  
>      if (!rtas_addr) {
> @@ -361,6 +363,18 @@ static void rtas_ibm_nmi_register(PowerPCCPU *cpu,
>          return;
>      }
>  
> +    ret = kvmppc_fwnmi_enable(cpu);

You shouldn't need this here as well as in cap_fwnmi_mce_apply().

Instead, you should unconditionally fail the nmi-register if the
capability is not enabled.

> +    if (ret == 1) {
> +        rtas_st(rets, 0, RTAS_OUT_NOT_SUPPORTED);
> +        return;
> +    }
> +
> +    if (ret < 0) {
> +        rtas_st(rets, 0, RTAS_OUT_HW_ERROR);
> +        return;
> +    }
> +
>      spapr->guest_machine_check_addr = rtas_ld(args, 1);
>      rtas_st(rets, 0, RTAS_OUT_SUCCESS);
>  }
> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> index 03f34bf..9d16ad1 100644
> --- a/include/hw/ppc/spapr.h
> +++ b/include/hw/ppc/spapr.h
> @@ -78,8 +78,10 @@ typedef enum {
>  #define SPAPR_CAP_LARGE_DECREMENTER     0x08
>  /* Count Cache Flush Assist HW Instruction */
>  #define SPAPR_CAP_CCF_ASSIST            0x09
> +/* FWNMI machine check handling */
> +#define SPAPR_CAP_FWNMI_MCE             0x0A
>  /* Num Caps */
> -#define SPAPR_CAP_NUM                   (SPAPR_CAP_CCF_ASSIST + 1)
> +#define SPAPR_CAP_NUM                   (SPAPR_CAP_FWNMI_MCE + 1)
>  
>  /*
>   * Capability Values
> diff --git a/target/ppc/kvm.c b/target/ppc/kvm.c
> index 5eedce8..9c7b71d 100644
> --- a/target/ppc/kvm.c
> +++ b/target/ppc/kvm.c
> @@ -83,6 +83,7 @@ static int cap_ppc_safe_indirect_branch;
>  static int cap_ppc_count_cache_flush_assist;
>  static int cap_ppc_nested_kvm_hv;
>  static int cap_large_decr;
> +static int cap_ppc_fwnmi;
>  
>  static uint32_t debug_inst_opcode;
>  
> @@ -150,6 +151,7 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
>      kvmppc_get_cpu_characteristics(s);
>      cap_ppc_nested_kvm_hv = kvm_vm_check_extension(s, KVM_CAP_PPC_NESTED_HV);
>      cap_large_decr = kvmppc_get_dec_bits();
> +    cap_ppc_fwnmi = kvm_check_extension(s, KVM_CAP_PPC_FWNMI);
>      /*
>       * Note: setting it to false because there is not such capability
>       * in KVM at this moment.
> @@ -2117,6 +2119,18 @@ void kvmppc_set_mpic_proxy(PowerPCCPU *cpu, int mpic_proxy)
>      }
>  }
>  
> +int kvmppc_fwnmi_enable(PowerPCCPU *cpu)
> +{
> +    CPUState *cs = CPU(cpu);
> +
> +    if (!cap_ppc_fwnmi) {
> +        return 1;
> +    }
> +
> +    return kvm_vcpu_enable_cap(cs, KVM_CAP_PPC_FWNMI, 0);
> +}
> +
> +
>  int kvmppc_smt_threads(void)
>  {
>      return cap_ppc_smt ? cap_ppc_smt : 1;
> diff --git a/target/ppc/kvm_ppc.h b/target/ppc/kvm_ppc.h
> index 6edc42f..28919d3 100644
> --- a/target/ppc/kvm_ppc.h
> +++ b/target/ppc/kvm_ppc.h
> @@ -27,6 +27,7 @@ void kvmppc_enable_h_page_init(void);
>  void kvmppc_set_papr(PowerPCCPU *cpu);
>  int kvmppc_set_compat(PowerPCCPU *cpu, uint32_t compat_pvr);
>  void kvmppc_set_mpic_proxy(PowerPCCPU *cpu, int mpic_proxy);
> +int kvmppc_fwnmi_enable(PowerPCCPU *cpu);
>  int kvmppc_smt_threads(void);
>  void kvmppc_hint_smt_possible(Error **errp);
>  int kvmppc_set_smt_threads(int smt);
> @@ -159,6 +160,11 @@ static inline void kvmppc_set_mpic_proxy(PowerPCCPU *cpu, int mpic_proxy)
>  {
>  }
>  
> +static inline int kvmppc_fwnmi_enable(PowerPCCPU *cpu)
> +{
> +    return 1;
> +}
> +
>  static inline int kvmppc_smt_threads(void)
>  {
>      return 1;
> 

-- 
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