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

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

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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


    if(!fwnmi_enabed)
         return H_FUNCTION;

or maybe H_NOT_AVAILABLE.

> 
> > 
> > > +        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 */
> 

-- 
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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