Re: [Qemu-devel] [Qemu-ppc] [PATCH v8 5/6] ppc: spapr: Enable FWNMI capability

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

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On Fri, May 10, 2019 at 12:45:29PM +0530, Aravinda Prasad wrote:
> 
> 
> On Friday 10 May 2019 12:16 PM, David Gibson wrote:
> > 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.
> 
> cap_fwnmi is not enabled by default, because if it is enabled by default
> them KVM will start routing machine check exceptions via guest exit
> instead of routing it to guest's 0x200.
> 
> During early boot since guest has not yet issued nmi-register, KVM is
> expected to route exceptions to 0x200. Therefore we enable cap_fwnmi
> only when a guest issues nmi-register.

Except that's not true - you enable it in cap_fwnmi_mce_apply() which
will be executed whenever the machine capability is enabled.

> Or we should take the approach of enabling this capability by default
> and then from QEMU route the error to 0x200 if guest has not issued
> nmi-register.
> 
> > 
> >> +    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

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