Re: [Qemu-ppc] [PATCH v9 1/6] ppc: spapr: Handle "ibm, nmi-register" and "ibm, nmi-interlock" RTAS calls

[Greg Kurz]

On Tue, 4 Jun 2019 11:38:31 +0530
Aravinda Prasad <address@hidden> wrote:

> On Monday 03 June 2019 04:47 PM, Greg Kurz wrote:
> > On Mon, 3 Jun 2019 12:12:43 +0200
> > Greg Kurz <address@hidden> wrote:
> >   
> >> On Wed, 29 May 2019 11:10:14 +0530
> >> Aravinda Prasad <address@hidden> 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 <address@hidden>
> >>> Reviewed-by: David Gibson <address@hidden>
> >>> ---    
> >>
> >> 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".
> > 
> > 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.  
> 
> When you say "expose a partially implemented FWNMI feature to the
> guest", do you mean while debugging/bisect we may end up with exposing
> the partially implemented FWNMI feature? Otherwise it is expected that

Yes, we don't want to break someone else's bisect.

> QEMU runs with all the 6 patches.
> 
> If that is the case, I will have the rtas nmi register functionality as
> the last patch in the series. This way we don't have to have spapr cap
> turned off first and later turned on. However, as mentioned earlier
> (when David raised the same concern), use of guest_machine_check_addr
> may look odd at other patches as it is set only during rtas nmi register.
> 

Why odd ?

> Or else, as a workaround, I can return RTAS_OUT_NOT_SUPPORTED for rtas
> nmi register till the entire functionality is implemented and only in
> the last patch in the series I will return RTAS_OUT_SUCCESS. This will
> ensure that we have a logical connection between the patches and the
> partially implemented fwnmi is not exposed to the guest kernel.
> 

Not exactly true. FWNMI would be exposed to the guest in the device tree
and the guest kernel would _just_ fail to set the fwnmi_active global:

        if (0 == rtas_call(ibm_nmi_register, 2, 1, NULL, system_reset_addr,
                                machine_check_addr))
                fwnmi_active = 1;

> Regards,
> Aravinda
> 
> 
> 
> 
> >   
> >>>  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;This means it isn't related to XIVE it to set
> >>>      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 */
> >>>     
> >>
> >>  
> >   
>