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

[Aravinda Prasad <aravinda@linux.vnet.ibm.com>]

On Thursday 06 June 2019 07:05 AM, David Gibson wrote:
> 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.

ok

> 
>> 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 */
>>>>   
>>>
>>>
>>
> 

-- 
Regards,
Aravinda