Re: [Qemu-devel] [PATCH 4/4] target-ppc: Handle NMI guest exit

[Aravinda Prasad <aravinda@linux.vnet.ibm.com>]

On Friday 13 November 2015 07:28 AM, David Gibson wrote:
> On Thu, Nov 12, 2015 at 11:53:45PM +0530, Aravinda Prasad wrote:
>>
>>
>> On Thursday 12 November 2015 01:39 PM, Thomas Huth wrote:
>>> On 11/11/15 18:16, 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
>>>> 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. If the guest OS
>>>> has registered the machine check handling routine by
>>>> calling "ibm,nmi-register", then the handler builds
>>>> the error log and invokes the registered handler else
>>>> invokes the handler at 0x200.
>>>>
>>>> [1] http://marc.info/?l=kvm-ppc&m=144726114408289
>>>>
>>>> Signed-off-by: Aravinda Prasad <aravinda@linux.vnet.ibm.com>
>>>> ---
>>>>  target-ppc/kvm.c     |   69 +++++++++++++++++++++++++++++++++++++++++++
>>>>  target-ppc/kvm_ppc.h |   81 ++++++++++++++++++++++++++++++++++++++++++++++++++
>>>>  2 files changed, 150 insertions(+)
>>>>
>>>> diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c
>>>> index 110436d..e2e5170 100644
>>>> --- a/target-ppc/kvm.c
>>>> +++ b/target-ppc/kvm.c
>>>> @@ -1665,6 +1665,11 @@ int kvm_arch_handle_exit(CPUState *cs, struct kvm_run *run)
>>>>          ret = 0;
>>>>          break;
>>>>  
>>>> +    case KVM_EXIT_NMI:
>>>> +        DPRINTF("handle NMI exception\n");
>>>> +        ret = kvm_handle_nmi(cpu);
>>>> +        break;
>>>> +
>>>>      default:
>>>>          fprintf(stderr, "KVM: unknown exit reason %d\n", run->exit_reason);
>>>>          ret = -1;
>>>> @@ -2484,3 +2489,67 @@ int kvm_arch_msi_data_to_gsi(uint32_t data)
>>>>  {
>>>>      return data & 0xffff;
>>>>  }
>>>> +
>>>> +int kvm_handle_nmi(PowerPCCPU *cpu)
>>>> +{
>>>> +    struct rtas_mc_log mc_log;
>>>> +    CPUPPCState *env = &cpu->env;
>>>> +    sPAPRMachineState *spapr = SPAPR_MACHINE(qdev_get_machine());
>>>> +    PowerPCCPUClass *pcc = POWERPC_CPU_GET_CLASS(cpu);
>>>> +
>>>> +    cpu_synchronize_state(CPU(ppc_env_get_cpu(env)));
>>>> +
>>>> +    /* Properly set bits in MSR before we invoke the handler */
>>>> +    env->msr = 0;
>>>> +
>>>> +    if (!(*pcc->interrupts_big_endian)(cpu)) {
>>>> +        env->msr |= (1ULL << MSR_LE);
>>>> +    }
>>>> +
>>>> +#ifdef TARGET_PPC64
>>>> +    env->msr |= (1ULL << MSR_SF);
>>>> +#endif
>>>> +
>>>> +    if (!spapr->guest_machine_check_addr) {
>>>> +        /*
>>>> +         * If OS has not registered with "ibm,nmi-register"
>>>> +         * jump to 0x200
>>>> +         */
>>>
>>> Shouldn't you also check MSR_ME here first and enter checkstop when
>>> machine checks are disabled?
>>
>> Yes, MSR_ME should be checked first.
>>
>>> Also I think you have to set up some more registers for machine check
>>> interrupts, like SRR0 and SRR1?
>>
>> SRRO and SRR1 of vcpu are properly set in KVM in kvmppc_interrupt_hv. I
>> am not sure if any other registers need to be set.
> 
> DAR and DSISR are the obvious ones you need to consider, although I
> suspect they're already set up correctly by the kernel, too.

Yes, they are also setup properly by KVM.

Regards,
Aravinda

> 

-- 
Regards,
Aravinda