Re: [PATCH v16 2/7] ppc: spapr: Introduce FWNMI capability

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

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On Thu, Oct 10, 2019 at 12:29:45PM +0530, Ganesh Goudar wrote:
> From: Aravinda Prasad <arawinda.p@gmail.com>
> 
> Introduce 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 introduces fwnmi-mce capability to
> deal 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.

I think the commit message needs some updating.  This doesn't really
introduce the KVM cap.  It introduces the spapr capability, and
validates it against the kernel's exising capability.

> 
> [eliminate cap_ppc_fwnmi]
> Signed-off-by: Ganesh Goudar <ganeshgr@linux.ibm.com>
> Signed-off-by: Aravinda Prasad <arawinda.p@gmail.com>
> ---
>  hw/ppc/spapr.c         |  1 +
>  hw/ppc/spapr_caps.c    | 29 +++++++++++++++++++++++++++++
>  include/hw/ppc/spapr.h |  4 +++-
>  target/ppc/kvm.c       |  8 ++++++++
>  target/ppc/kvm_ppc.h   |  6 ++++++
>  5 files changed, 47 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 514a17ae74..7e6a15c9b4 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -4441,6 +4441,7 @@ 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_dual;
>      smc->dr_phb_enabled = true;

To have migration work correctly, you also need to add
&vmstate_spapr_cap_fwnmi_mce  to the list in vmstate_spapr.  (Yes,
that makes three places you have to put things to get migration
right, which is really easy to mess up - I've done it more than once
myself - unfortunately, I haven't come up with a better way yet).

> diff --git a/hw/ppc/spapr_caps.c b/hw/ppc/spapr_caps.c
> index 481dfd2a27..778bf32181 100644
> --- a/hw/ppc/spapr_caps.c
> +++ b/hw/ppc/spapr_caps.c
> @@ -496,6 +496,25 @@ static void cap_ccf_assist_apply(SpaprMachineState *spapr, uint8_t val,
>      }
>  }
>  
> +static void cap_fwnmi_mce_apply(SpaprMachineState *spapr, uint8_t val,
> +                                Error **errp)
> +{
> +    if (!val) {
> +        return; /* Disabled by default */
> +    }
> +
> +    if (tcg_enabled()) {
> +        /*
> +         * TCG support may not be correct in some conditions (e.g., in case
> +         * of software injected faults like duplicate SLBs).
> +         */
> +        warn_report("Firmware Assisted Non-Maskable Interrupts not supported in TCG");
> +    } else if (kvm_enabled() && kvmppc_set_fwnmi()) {

When checking integer error code return values (like
kvmppc_set_fwnmi()) please include an explicit != 0, to make it
clearer that's what's happening, rather than a function returning a bool.

> +        error_setg(errp,
> +"Firmware Assisted Non-Maskable Interrupts not supported by KVM, try cap-fwnmi-mce=off");
> +    }
> +}
> +
>  SpaprCapabilityInfo capability_table[SPAPR_CAP_NUM] = {
>      [SPAPR_CAP_HTM] = {
>          .name = "htm",
> @@ -595,6 +614,15 @@ 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,
> @@ -734,6 +762,7 @@ SPAPR_CAP_MIG_STATE(hpt_maxpagesize, SPAPR_CAP_HPT_MAXPAGESIZE);
>  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/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> index cbd1a4c9f3..dcd2e7d0cc 100644
> --- a/include/hw/ppc/spapr.h
> +++ b/include/hw/ppc/spapr.h
> @@ -79,8 +79,10 @@ 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 820724cc7d..d56f11a883 100644
> --- a/target/ppc/kvm.c
> +++ b/target/ppc/kvm.c
> @@ -2060,6 +2060,14 @@ void kvmppc_set_mpic_proxy(PowerPCCPU *cpu, int mpic_proxy)
>      }
>  }
>  
> +int kvmppc_set_fwnmi(void)
> +{
> +    PowerPCCPU *cpu = POWERPC_CPU(first_cpu);
> +    CPUState *cs = CPU(cpu);
> +
> +    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 98bd7d5da6..5727a5025f 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_set_fwnmi(void);
>  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_set_fwnmi(void)
> +{
> +    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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