Re: [Qemu-devel] [Qemu-ppc] [PATCH v8 1/6] ppc: spapr: Handle "ibm, nmi-register" and "ibm, nmi-interlock" RTAS calls

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

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On Fri, May 10, 2019 at 11:06:04AM +0200, Greg Kurz wrote:
> On Mon, 22 Apr 2019 12:32:58 +0530
> Aravinda Prasad <aravinda@linux.vnet.ibm.com> wrote:
> 
> > 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. This patch implements the
> > releasing part of the error-log while subsequent patch
> > (which builds error log) handles the locking part.
> > 
> > Signed-off-by: Aravinda Prasad <aravinda@linux.vnet.ibm.com>
> > ---
> >  hw/ppc/spapr.c         |   18 ++++++++++++++
> >  hw/ppc/spapr_rtas.c    |   61 ++++++++++++++++++++++++++++++++++++++++++++++++
> >  include/hw/ppc/spapr.h |    9 ++++++-
> >  3 files changed, 87 insertions(+), 1 deletion(-)
> > 
> > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > index c56939a..6642cb5 100644
> > --- a/hw/ppc/spapr.c
> > +++ b/hw/ppc/spapr.c
> > @@ -1805,6 +1805,11 @@ static void spapr_machine_reset(void)
> >      first_ppc_cpu->env.gpr[5] = 0;
> >  
> >      spapr->cas_reboot = false;
> > +
> > +    spapr->guest_machine_check_addr = -1;
> > +
> > +    /* Signal all vCPUs waiting on this condition */
> > +    qemu_cond_broadcast(&spapr->mc_delivery_cond);
> >  }
> >  
> >  static void spapr_create_nvram(SpaprMachineState *spapr)
> > @@ -2095,6 +2100,16 @@ static const VMStateDescription vmstate_spapr_dtb = {
> >      },
> >  };
> >  
> > +static const VMStateDescription vmstate_spapr_machine_check = {
> > +    .name = "spapr_machine_check",
> > +    .version_id = 1,
> > +    .minimum_version_id = 1,
> > +    .fields = (VMStateField[]) {
> > +        VMSTATE_UINT64(guest_machine_check_addr, SpaprMachineState),
> > +        VMSTATE_END_OF_LIST()
> > +    },
> 
> This VMState descriptor is missing a .needed field because we only want
> to migrate the subsection if the guest has called NMI register, ie.
> spapr->guest_machine_check_addr != (target_ulong) -1.
> 
> > +};
> > +
> >  static const VMStateDescription vmstate_spapr = {
> >      .name = "spapr",
> >      .version_id = 3,
> > @@ -2127,6 +2142,7 @@ static const VMStateDescription vmstate_spapr = {
> >          &vmstate_spapr_dtb,
> >          &vmstate_spapr_cap_large_decr,
> >          &vmstate_spapr_cap_ccf_assist,
> > +        &vmstate_spapr_machine_check,
> >          NULL
> >      }
> >  };
> > @@ -3068,6 +3084,8 @@ static void spapr_machine_init(MachineState *machine)
> >  
> >          kvmppc_spapr_enable_inkernel_multitce();
> >      }
> > +
> > +    qemu_cond_init(&spapr->mc_delivery_cond);
> >  }
> >  
> >  static int spapr_kvm_type(MachineState *machine, const char *vm_type)
> > diff --git a/hw/ppc/spapr_rtas.c b/hw/ppc/spapr_rtas.c
> > index ee24212..c2f3991 100644
> > --- a/hw/ppc/spapr_rtas.c
> > +++ b/hw/ppc/spapr_rtas.c
> > @@ -348,6 +348,39 @@ 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)
> > +{
> > +    uint64_t 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) {
> 
> Hmm... the default value is -1. It looks like the check should rather be:
> 
>     if (spapr->guest_machine_check_addr == (target_ulong) -1) {
> 
> 
> > +        /* NMI register not called */
> > +        rtas_st(rets, 0, RTAS_OUT_PARAM_ERROR);
> > +    } else {
> > +        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;
> > @@ -466,6 +499,30 @@ void spapr_load_rtas(SpaprMachineState *spapr, void *fdt, hwaddr addr)
> >      }
> >  }
> >  
> > +uint64_t spapr_get_rtas_addr(void)
> 
> Shouldn't this be hwaddr instead of uint64_t ?
> 
> > +{
> > +    SpaprMachineState *spapr = SPAPR_MACHINE(qdev_get_machine());
> > +    int rtas_node;
> > +    const struct fdt_property *rtas_addr_prop;
> > +    void *fdt = spapr->fdt_blob;
> > +    uint32_t rtas_addr;
> > +
> > +    /* fetch rtas addr from fdt */
> > +    rtas_node = fdt_path_offset(fdt, "/rtas");
> > +    if (rtas_node == 0) {
> > +        return 0;
> > +    }
> > +
> > +    rtas_addr_prop = fdt_get_property(fdt, rtas_node, "linux,rtas-base", NULL);
> > +    if (!rtas_addr_prop) {
> 
> Just for curiosity: this is ok for linux, but what about other OSes (eg. AIX) ?
> 
> > +        return 0;
> > +    }
> > +
> > +    rtas_addr = fdt32_to_cpu(*(uint32_t *)rtas_addr_prop->data);
> 
> Also this assumes the OS called RTAS instantiate-rtas, but some other
> OS might have called RTAS instantiate-rtas-64 instead. I guess it is
> ok for now because SLOF only provides the 32-bit variant, but a
> comment would certainly help IMHO.

I have a feeling kvm-unit-tests may not call instantiate-rtas at all.

-- 
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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