Re: [Qemu-devel] [PATCH v7 5/6] ppc: spapr: Enable FWNMI capability

[Aravinda Prasad]

On Monday 25 March 2019 12:02 PM, David Gibson wrote:
> On Fri, Mar 22, 2019 at 12:04:16PM +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.
>>
>> Signed-off-by: Aravinda Prasad <address@hidden>
>> ---
>>  hw/ppc/spapr_rtas.c  |   15 +++++++++++++++
>>  target/ppc/kvm.c     |   14 ++++++++++++++
>>  target/ppc/kvm_ppc.h |    6 ++++++
>>  3 files changed, 35 insertions(+)
>>
>> diff --git a/hw/ppc/spapr_rtas.c b/hw/ppc/spapr_rtas.c
>> index fb594a4..939f428 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 +355,20 @@ static void rtas_ibm_nmi_register(PowerPCCPU *cpu,
>>                                    target_ulong args,
>>                                    uint32_t nret, target_ulong rets)
>>  {
>> +    int ret;
>> +
>> +    ret = kvmppc_fwnmi_enable(cpu);
>> +
>> +    if (ret == 1) {
>> +        rtas_st(rets, 0, RTAS_OUT_NOT_SUPPORTED);
> 
> Urgh, we're here making a guest visible different to the environment
> depending on a host (KVM) capability.  What happens if you start a
> guest and it registers fwnmi support, then migrate it to a host that
> lacks the necessary KVM support?

I just checked how such scenarios are handled for other KVM
capabilities. Should I need to add an Spapr cap for this?

Regards,
Aravinda

> 
>> +        return;
>> +    }
>> +
>> +    if (ret < 0) {
>> +        rtas_st(rets, 0, RTAS_OUT_HW_ERROR);
>> +        return;
>> +    }
>> +
>>      spapr->mc_reset = 0;
>>      spapr->guest_machine_check_addr = rtas_ld(args, 1);
>>      rtas_st(rets, 0, RTAS_OUT_SUCCESS);
>> diff --git a/target/ppc/kvm.c b/target/ppc/kvm.c
>> index a593448..161b45e 100644
>> --- a/target/ppc/kvm.c
>> +++ b/target/ppc/kvm.c
>> @@ -93,6 +93,7 @@ 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;
>>  
>> @@ -155,6 +156,7 @@ 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.
>> @@ -2091,6 +2093,18 @@ 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 df5e85f..cf7b24f 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);
>> @@ -158,6 +159,11 @@ static inline void kvmppc_set_mpic_proxy(PowerPCCPU 
>> *cpu, int mpic_proxy)
>>  {
>>  }
>>  
>> +int kvmppc_fwnmi_enable(PowerPCCPU *cpu)
>> +{
>> +    return 1;
>> +}
>> +
>>  static inline int kvmppc_smt_threads(void)
>>  {
>>      return 1;
>>
> 

-- 
Regards,
Aravinda