Re: [PATCH v18 5/7] ppc: spapr: Handle "ibm,nmi-register" and "ibm,nmi-interlock" RTAS calls

[Ganesh <ganeshgr@linux.ibm.com>]

On 1/8/20 6:34 AM, David Gibson wrote:
> On Tue, Jan 07, 2020 at 11:57:08AM +0530, Ganesh wrote:
>> On 1/3/20 7:49 AM, David Gibson wrote:
>>> On Thu, Jan 02, 2020 at 01:21:09PM +0530, Ganesh Goudar wrote:
>>>> From: Aravinda Prasad <arawinda.p@gmail.com>
>>>>
>>>> This patch adds support in QEMU to handle "ibm,nmi-register"
>>>> and "ibm,nmi-interlock" RTAS calls.
>>>>
>>>> The machine check notification address is saved when the
>>>> OS issues "ibm,nmi-register" RTAS call.
>>>>
>>>> This patch also handles the case when multiple processors
>>>> experience machine check at or about the same time by
>>>> handling "ibm,nmi-interlock" call. In such cases, as per
>>>> PAPR, subsequent processors serialize waiting for the first
>>>> processor to issue the "ibm,nmi-interlock" call. The second
>>>> processor that also received a machine check error waits
>>>> till the first processor is done reading the error log.
>>>> The first processor issues "ibm,nmi-interlock" call
>>>> when the error log is consumed.
>>>>
>>>> [Move fwnmi registration to .apply hook]
>>>> Signed-off-by: Ganesh Goudar <ganeshgr@linux.ibm.com>
>>>> Signed-off-by: Aravinda Prasad <arawinda.p@gmail.com>
>>>> ---
>>>>    hw/ppc/spapr_caps.c    |  6 +++++
>>>>    hw/ppc/spapr_rtas.c    | 58 ++++++++++++++++++++++++++++++++++++++++++
>>>>    include/hw/ppc/spapr.h |  7 ++++-
>>>>    3 files changed, 70 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/hw/ppc/spapr_caps.c b/hw/ppc/spapr_caps.c
>>>> index 3001098601..e922419cfb 100644
>>>> --- a/hw/ppc/spapr_caps.c
>>>> +++ b/hw/ppc/spapr_caps.c
>>>> @@ -502,6 +502,12 @@ static void cap_fwnmi_mce_apply(SpaprMachineState *spapr, uint8_t val,
>>>>        if (!val) {
>>>>            return; /* Disabled by default */
>>>>        }
>>>> +
>>>> +    if (!spapr->fwnmi_calls_registered && !kvmppc_set_fwnmi()) {
>>> So, we definitely need the kvmppc_set_fwnmi() call here.  But in the
>>> case where we *do* have KVM, but the call fails, we should fail the
>>> .apply hook, rather than ignoring it silently.
>>>
>>> As we've discussed although TCG behaviour with fwnmi isn't 100%
>>> correct, it's close enough to pass for most purposes - so it's
>>> reasonable to continue if the cap is selected.  But if the cap is
>>> selected and we're running with KVM we *must* enable the capability in
>>> KVM or we're not providing the environment the user requested.
>>>
>>>> +        /* Register ibm,nmi-register and ibm,nmi-interlock RTAS calls */
>>>> +        spapr_fwnmi_register();
>>> We discussed registering the hypercalls here, but I thought after that
>>> I suggested just always registering them, and having them bail out
>>> when called if the cap is not set.  I see that you've implemented that
>>> bailout for register, though not for interlock.  I think that's
>>> simpler than registering them here.
>> something like this?, with bailout in interlock as well.
>>
>> {
>>      if (!val) {
>>          return; /* Disabled by default */
>>      }
>>
>>      if (kvm_enabled()) {
>>          if (kvmppc_set_fwnmi() < 0) {
>>              error_report("Could not enable fwnmi capability");
>>              exit(1)
>>      }
>>
>>      if (!spapr->fwnmi_calls_registered) {
>>          /* Register ibm,nmi-register and ibm,nmi-interlock RTAS calls */
>>          spapr_fwnmi_register();
>>          spapr->fwnmi_calls_registered = true;
>>      }
>> }
> Uh.. no.. not really.  I was suggesting registering the calls
> unconditionally, but in each of the call implementations you have
Yes I got your point, here I am just trying to avoid registering the
calls more than once, otherwise we may hit an assert.
>
>
>      if(!fwnmi_enabed)
>           return H_FUNCTION;
>
> or maybe H_NOT_AVAILABLE.
Sure, ill add this check in interlock call also.
>
>>>> +        spapr->fwnmi_calls_registered = true;
>>>> +    }
>>>>    }
>>>>    SpaprCapabilityInfo capability_table[SPAPR_CAP_NUM] = {
>>>> diff --git a/hw/ppc/spapr_rtas.c b/hw/ppc/spapr_rtas.c
>>>> index 2c066a372d..54b142f35b 100644
>>>> --- a/hw/ppc/spapr_rtas.c
>>>> +++ b/hw/ppc/spapr_rtas.c
>>>> @@ -400,6 +400,56 @@ static void rtas_get_power_level(PowerPCCPU *cpu, SpaprMachineState *spapr,
>>>>        rtas_st(rets, 1, 100);
>>>>    }
>>>> +static void rtas_ibm_nmi_register(PowerPCCPU *cpu,
>>>> +                                  SpaprMachineState *spapr,
>>>> +                                  uint32_t token, uint32_t nargs,
>>>> +                                  target_ulong args,
>>>> +                                  uint32_t nret, target_ulong rets)
>>>> +{
>>>> +    hwaddr rtas_addr;
>>>> +
>>>> +    if (spapr_get_cap(spapr, SPAPR_CAP_FWNMI_MCE) == SPAPR_CAP_OFF) {
>>>> +        rtas_st(rets, 0, RTAS_OUT_NOT_SUPPORTED);
>>>> +        return;
>>>> +    }
>>>> +
>>>> +    rtas_addr = spapr_get_rtas_addr();
>>>> +    if (!rtas_addr) {
>>>> +        rtas_st(rets, 0, RTAS_OUT_NOT_SUPPORTED);
>>>> +        return;
>>>> +    }
>>>> +
>>>> +    spapr->guest_machine_check_addr = rtas_ld(args, 1);
>>>> +    rtas_st(rets, 0, RTAS_OUT_SUCCESS);
>>>> +}
>>>> +
>>>> +static void rtas_ibm_nmi_interlock(PowerPCCPU *cpu,
>>>> +                                   SpaprMachineState *spapr,
>>>> +                                   uint32_t token, uint32_t nargs,
>>>> +                                   target_ulong args,
>>>> +                                   uint32_t nret, target_ulong rets)
>>>> +{
>>>> +    if (spapr->guest_machine_check_addr == -1) {
>>>> +        /* NMI register not called */
>>>> +        rtas_st(rets, 0, RTAS_OUT_PARAM_ERROR);
>>>> +        return;
>>>> +    }
>>>> +
>>>> +    if (spapr->mc_status != cpu->vcpu_id) {
>>>> +        /* The vCPU that hit the NMI should invoke "ibm,nmi-interlock" */
>>>> +        rtas_st(rets, 0, RTAS_OUT_PARAM_ERROR);
>>>> +        return;
>>>> +    }
>>>> +
>>>> +    /*
>>>> +     * vCPU issuing "ibm,nmi-interlock" is done with NMI handling,
>>>> +     * hence unset mc_status.
>>>> +     */
>>>> +    spapr->mc_status = -1;
>>>> +    qemu_cond_signal(&spapr->mc_delivery_cond);
>>>> +    rtas_st(rets, 0, RTAS_OUT_SUCCESS);
>>>> +}
>>>> +
>>>>    static struct rtas_call {
>>>>        const char *name;
>>>>        spapr_rtas_fn fn;
>>>> @@ -503,6 +553,14 @@ hwaddr spapr_get_rtas_addr(void)
>>>>        return (hwaddr)fdt32_to_cpu(*rtas_data);
>>>>    }
>>>> +void spapr_fwnmi_register(void)
>>>> +{
>>>> +    spapr_rtas_register(RTAS_IBM_NMI_REGISTER, "ibm,nmi-register",
>>>> +                        rtas_ibm_nmi_register);
>>>> +    spapr_rtas_register(RTAS_IBM_NMI_INTERLOCK, "ibm,nmi-interlock",
>>>> +                        rtas_ibm_nmi_interlock);
>>>> +}
>>>> +
>>>>    static void core_rtas_register_types(void)
>>>>    {
>>>>        spapr_rtas_register(RTAS_DISPLAY_CHARACTER, "display-character",
>>>> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
>>>> index 652a5514e8..a90e677cc3 100644
>>>> --- a/include/hw/ppc/spapr.h
>>>> +++ b/include/hw/ppc/spapr.h
>>>> @@ -218,6 +218,8 @@ struct SpaprMachineState {
>>>>        unsigned gpu_numa_id;
>>>>        SpaprTpmProxy *tpm_proxy;
>>>> +
>>>> +    bool fwnmi_calls_registered;
>>>>    };
>>>>    #define H_SUCCESS         0
>>>> @@ -656,8 +658,10 @@ target_ulong spapr_hypercall(PowerPCCPU *cpu, target_ulong opcode,
>>>>    #define RTAS_IBM_REMOVE_PE_DMA_WINDOW           (RTAS_TOKEN_BASE + 0x28)
>>>>    #define RTAS_IBM_RESET_PE_DMA_WINDOW            (RTAS_TOKEN_BASE + 0x29)
>>>>    #define RTAS_IBM_SUSPEND_ME                     (RTAS_TOKEN_BASE + 0x2A)
>>>> +#define RTAS_IBM_NMI_REGISTER                   (RTAS_TOKEN_BASE + 0x2B)
>>>> +#define RTAS_IBM_NMI_INTERLOCK                  (RTAS_TOKEN_BASE + 0x2C)
>>>> -#define RTAS_TOKEN_MAX                          (RTAS_TOKEN_BASE + 0x2B)
>>>> +#define RTAS_TOKEN_MAX                          (RTAS_TOKEN_BASE + 0x2D)
>>>>    /* RTAS ibm,get-system-parameter token values */
>>>>    #define RTAS_SYSPARM_SPLPAR_CHARACTERISTICS      20
>>>> @@ -908,4 +912,5 @@ void spapr_check_pagesize(SpaprMachineState *spapr, hwaddr pagesize,
>>>>    void spapr_set_all_lpcrs(target_ulong value, target_ulong mask);
>>>>    hwaddr spapr_get_rtas_addr(void);
>>>> +void spapr_fwnmi_register(void);
>>>>    #endif /* HW_SPAPR_H */