Re: [Qemu-devel] [Qemu-ppc] [PATCH v9 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 Mon, Jun 03, 2019 at 01:17:23PM +0200, Greg Kurz wrote:
> On Mon, 3 Jun 2019 12:12:43 +0200
> Greg Kurz <groug@kaod.org> wrote:
> 
> > On Wed, 29 May 2019 11:10:14 +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>
> > > Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
> > > ---  
> > 
> > The code looks okay but it still seems wrong to advertise the RTAS
> > calls to the guest that early in the series. The linux kernel in
> > the guest will assume FWNMI is functional, which isn't true until
> > patch 6 (yes, migration is part of the feature, it should be
> > supported upfront, not fixed afterwards).
> > 
> > It doesn't help much to introduce the RTAS calls early and to
> > modify them in the other patches. I'd rather see the rest of
> > the code first and a final patch that introduces the fully
> > functional RTAS calls and calls spapr_rtas_register().
> > 
> 
> Thinking again, you should introduce the "fwnmi-mce" spapr capability in
> its own patch first, default to "off" and and have the last patch in the
> series to switch the default to "on" for newer machine types only.
> 
> This patch should then only register the RTAS calls if "fwnmi-mcr" is set
> to "on".

Yes, I think this is a good approach.

> This should address the fact that we don't want to expose a partially
> implemented FWNMI feature to the guest, and we don't want to support
> FWNMI at all with older machine types for the sake of compatibility.
> 
> > >  hw/ppc/spapr.c         |    7 +++++
> > >  hw/ppc/spapr_rtas.c    |   65 ++++++++++++++++++++++++++++++++++++++++++++++++
> > >  include/hw/ppc/spapr.h |    9 ++++++-
> > >  3 files changed, 80 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > > index e2b33e5..fae28a9 100644
> > > --- a/hw/ppc/spapr.c
> > > +++ b/hw/ppc/spapr.c
> > > @@ -1808,6 +1808,11 @@ 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)
> > > @@ -3072,6 +3077,8 @@ 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 5bc1a93..e7509cf 100644
> > > --- a/hw/ppc/spapr_rtas.c
> > > +++ b/hw/ppc/spapr_rtas.c
> > > @@ -352,6 +352,38 @@ 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 = 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);
> > > +    } 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;
> > > @@ -470,6 +502,35 @@ void spapr_load_rtas(SpaprMachineState *spapr, void *fdt, hwaddr addr)
> > >      }
> > >  }
> > >  
> > > +hwaddr spapr_get_rtas_addr(void)
> > > +{
> > > +    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) {
> > > +        return 0;
> > > +    }
> > > +
> > > +    /*
> > > +     * We assume that the OS called RTAS instantiate-rtas, but some other
> > > +     * OS might call RTAS instantiate-rtas-64 instead. This fine as of now
> > > +     * as SLOF only supports 32-bit variant.
> > > +     */
> > > +    rtas_addr = fdt32_to_cpu(*(uint32_t *)rtas_addr_prop->data);
> > > +    return (hwaddr)rtas_addr;
> > > +}
> > > +
> > > +
> > >  static void core_rtas_register_types(void)
> > >  {
> > >      spapr_rtas_register(RTAS_DISPLAY_CHARACTER, "display-character",
> > > @@ -493,6 +554,10 @@ static void core_rtas_register_types(void)
> > >                          rtas_set_power_level);
> > >      spapr_rtas_register(RTAS_GET_POWER_LEVEL, "get-power-level",
> > >                          rtas_get_power_level);
> > > +    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);
> > >  }
> > >  
> > >  type_init(core_rtas_register_types)
> > > diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> > > index 4f5becf..9dc5e30 100644
> > > --- a/include/hw/ppc/spapr.h
> > > +++ b/include/hw/ppc/spapr.h
> > > @@ -188,6 +188,10 @@ struct SpaprMachineState {
> > >       * occurs during the unplug process. */
> > >      QTAILQ_HEAD(, SpaprDimmState) pending_dimm_unplugs;
> > >  
> > > +    /* State related to "ibm,nmi-register" and "ibm,nmi-interlock" calls */
> > > +    target_ulong guest_machine_check_addr;
> > > +    QemuCond mc_delivery_cond;
> > > +
> > >      /*< public >*/
> > >      char *kvm_type;
> > >      char *host_model;
> > > @@ -624,8 +628,10 @@ target_ulong spapr_hypercall(PowerPCCPU *cpu, target_ulong opcode,
> > >  #define RTAS_IBM_CREATE_PE_DMA_WINDOW           (RTAS_TOKEN_BASE + 0x27)
> > >  #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_NMI_REGISTER                   (RTAS_TOKEN_BASE + 0x2A)
> > > +#define RTAS_IBM_NMI_INTERLOCK                  (RTAS_TOKEN_BASE + 0x2B)
> > >  
> > > -#define RTAS_TOKEN_MAX                          (RTAS_TOKEN_BASE + 0x2A)
> > > +#define RTAS_TOKEN_MAX                          (RTAS_TOKEN_BASE + 0x2C)
> > >  
> > >  /* RTAS ibm,get-system-parameter token values */
> > >  #define RTAS_SYSPARM_SPLPAR_CHARACTERISTICS      20
> > > @@ -876,4 +882,5 @@ void spapr_check_pagesize(SpaprMachineState *spapr, hwaddr pagesize,
> > >  #define SPAPR_OV5_XIVE_BOTH     0x80 /* Only to advertise on the platform */
> > >  
> > >  void spapr_set_all_lpcrs(target_ulong value, target_ulong mask);
> > > +uint64_t spapr_get_rtas_addr(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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