Re: [Qemu-devel] [PATCH v10 6/6] ppc: spapr: Handle "ibm, nmi-register" and "ibm, nmi-interlock" RTAS calls

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

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On Wed, Jun 12, 2019 at 02:51:38PM +0530, Aravinda Prasad wrote:
> This patch adds support in QEMU to handle "ibm,nmi-register"
> and "ibm,nmi-interlock" RTAS calls and sets the default
> value of SPAPR_CAP_FWNMI_MCE to SPAPR_CAP_ON for machine
> type 4.0.
> 
> 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.
> 
> Signed-off-by: Aravinda Prasad <aravinda@linux.vnet.ibm.com>
> ---
>  hw/ppc/spapr.c         |    6 ++++-
>  hw/ppc/spapr_rtas.c    |   63 ++++++++++++++++++++++++++++++++++++++++++++++++
>  include/hw/ppc/spapr.h |    5 +++-
>  3 files changed, 72 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 3d6d139..213d493 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -2946,6 +2946,9 @@ static void spapr_machine_init(MachineState *machine)
>          /* Create the error string for live migration blocker */
>          error_setg(&spapr->fwnmi_migration_blocker,
>                  "Live migration not supported during machine check handling");
> +
> +        /* Register ibm,nmi-register and ibm,nmi-interlock RTAS calls */
> +        spapr_fwnmi_register();
>      }
>  
>      spapr->rtas_blob = g_malloc(spapr->rtas_size);
> @@ -4408,7 +4411,7 @@ static void spapr_machine_class_init(ObjectClass *oc, void *data)
>      smc->default_caps.caps[SPAPR_CAP_NESTED_KVM_HV] = SPAPR_CAP_OFF;
>      smc->default_caps.caps[SPAPR_CAP_LARGE_DECREMENTER] = SPAPR_CAP_ON;
>      smc->default_caps.caps[SPAPR_CAP_CCF_ASSIST] = SPAPR_CAP_OFF;
> -    smc->default_caps.caps[SPAPR_CAP_FWNMI_MCE] = SPAPR_CAP_OFF;
> +    smc->default_caps.caps[SPAPR_CAP_FWNMI_MCE] = SPAPR_CAP_ON;

Turning this on by default really isn't ok if it stops you running TCG
guests at all.

>      spapr_caps_add_properties(smc, &error_abort);
>      smc->irq = &spapr_irq_dual;
>      smc->dr_phb_enabled = true;
> @@ -4512,6 +4515,7 @@ static void spapr_machine_3_1_class_options(MachineClass *mc)
>      smc->default_caps.caps[SPAPR_CAP_SBBC] = SPAPR_CAP_BROKEN;
>      smc->default_caps.caps[SPAPR_CAP_IBS] = SPAPR_CAP_BROKEN;
>      smc->default_caps.caps[SPAPR_CAP_LARGE_DECREMENTER] = SPAPR_CAP_OFF;
> +    smc->default_caps.caps[SPAPR_CAP_FWNMI_MCE] = SPAPR_CAP_OFF;

We're now well past 4.0, and in fact we're about to go into soft
freeze for 4.1, so we're going to miss that too.  So 4.1 and earlier
will need to retain the old default.

>  }
>  
>  DEFINE_SPAPR_MACHINE(3_1, "3.1", false);
> diff --git a/hw/ppc/spapr_rtas.c b/hw/ppc/spapr_rtas.c
> index a015a80..e010cb2 100644
> --- a/hw/ppc/spapr_rtas.c
> +++ b/hw/ppc/spapr_rtas.c
> @@ -49,6 +49,7 @@
>  #include "hw/ppc/fdt.h"
>  #include "target/ppc/mmu-hash64.h"
>  #include "target/ppc/mmu-book3s-v3.h"
> +#include "migration/blocker.h"
>  
>  static void rtas_display_character(PowerPCCPU *cpu, SpaprMachineState *spapr,
>                                     uint32_t token, uint32_t nargs,
> @@ -352,6 +353,60 @@ 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)
> +{
> +    int ret;
> +    hwaddr rtas_addr = spapr_get_rtas_addr();
> +
> +    if (!rtas_addr) {
> +        rtas_st(rets, 0, RTAS_OUT_NOT_SUPPORTED);
> +        return;
> +    }
> +
> +    if (spapr_get_cap(spapr, SPAPR_CAP_FWNMI_MCE) == SPAPR_CAP_OFF) {
> +        rtas_st(rets, 0, RTAS_OUT_NOT_SUPPORTED);
> +        return;
> +    }
> +
> +    ret = kvmppc_fwnmi_enable(cpu);
> +    if (ret == 1) {
> +        rtas_st(rets, 0, RTAS_OUT_NOT_SUPPORTED);

I don't understand this case separate from the others.  We've already
set the cap, so fwnmi support should be checked and available.

> +        return;
> +    } else if (ret < 0) {
> +        error_report("Couldn't enable KVM FWNMI capability");
> +        rtas_st(rets, 0, RTAS_OUT_HW_ERROR);
> +        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 {
> +        /*
> +         * 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);
> +        migrate_del_blocker(spapr->fwnmi_migration_blocker);

Hrm.  We add the blocker at the mce request point.  First, that's in
another patch, which isn't great.  Second, does that mean we could add
multiple times if we get an MCE on multiple CPUs?  Will that work and
correctly match adds and removes properly?

> +        rtas_st(rets, 0, RTAS_OUT_SUCCESS);
> +    }
> +}
> +
>  static struct rtas_call {
>      const char *name;
>      spapr_rtas_fn fn;
> @@ -496,6 +551,14 @@ 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 0dedf0a..7ae53e2 100644
> --- a/include/hw/ppc/spapr.h
> +++ b/include/hw/ppc/spapr.h
> @@ -637,8 +637,10 @@ 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
> @@ -894,4 +896,5 @@ 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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