Re: [Qemu-devel] [PATCH v5 1/4] spapr: Implement VPA dispatch counter and prod bit on tcg

["Cédric Le Goater" <clg@kaod.org>]

On 17/07/2019 07:39, Nicholas Piggin wrote:
> Implement cpu_exec_enter/exit on ppc which calls into new methods of
> the same name in PPCVirtualHypervisorClass. These are used by spapr
> to implement these splpar elements, used in subsequent changes.
> 
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>

This is nice. I am thinking of using these handlers to push/pull 
the XIVE OS CAM line and escalate to QEMU when a vCPU being notified 
is not dispatched.

Some minor comments below.

Reviewed-by: Cédric Le Goater <clg@kaod.org>


Thanks,

C.

> ---
> Changes since v4:
> - Store to VPA on the way out as well.
> - Increment the dispatch counter directly in the VPA, which means it will
>   migrate with guest memory the same as KVM.
> - Prod need not be migrated, add a comment.
> 
>  hw/ppc/spapr.c                  | 41 +++++++++++++++++++++++++++++++++
>  hw/ppc/spapr_cpu_core.c         |  4 +++-
>  hw/ppc/spapr_hcall.c            |  5 ----
>  include/hw/ppc/spapr.h          |  7 ++++++
>  include/hw/ppc/spapr_cpu_core.h |  1 +
>  target/ppc/cpu.h                |  2 ++
>  target/ppc/translate_init.inc.c | 25 ++++++++++++++++++++
>  7 files changed, 79 insertions(+), 6 deletions(-)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 821f0d4a49..13c423347e 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -4302,6 +4302,45 @@ PowerPCCPU *spapr_find_cpu(int vcpu_id)
>      return NULL;
>  }
>  
> +static void spapr_cpu_exec_enter(PPCVirtualHypervisor *vhyp, PowerPCCPU *cpu)
> +{
> +    SpaprCpuState *spapr_cpu = spapr_cpu_state(cpu);
> +
> +    /* These are only called by TCG, KVM maintains dispatch state */
> +
> +    spapr_cpu->prod = false;

I would have kept this prod bool for the next patch as we don't use it here.

> +    if (spapr_cpu->vpa_addr) {
> +        CPUState *cs = CPU(cpu);
> +        unsigned int dispatch;
> +
> +        dispatch = ldl_be_phys(cs->as,
> +                               spapr_cpu->vpa_addr + VPA_DISPATCH_COUNTER);
> +        dispatch++;
> +        if ((dispatch & 1) != 0) /* guest set the "wrong" value */
> +            dispatch++;


You might want to add :

  qemu_log_mask(LOG_GUEST_ERROR, ...);  

when the yield value is wrong.

> +        stl_be_phys(cs->as,
> +                    spapr_cpu->vpa_addr + VPA_DISPATCH_COUNTER, dispatch);
> +    }
> +}
> +
> +static void spapr_cpu_exec_exit(PPCVirtualHypervisor *vhyp, PowerPCCPU *cpu)
> +{
> +    SpaprCpuState *spapr_cpu = spapr_cpu_state(cpu);
> +
> +    if (spapr_cpu->vpa_addr) {
> +        CPUState *cs = CPU(cpu);
> +        unsigned int dispatch;
> +
> +        dispatch = ldl_be_phys(cs->as,
> +                               spapr_cpu->vpa_addr + VPA_DISPATCH_COUNTER);
> +        dispatch++;
> +        if ((dispatch & 1) != 1) /* guest set the "wrong" value */
> +            dispatch++;
> +        stl_be_phys(cs->as,
> +                    spapr_cpu->vpa_addr + VPA_DISPATCH_COUNTER, dispatch);
> +    }
> +}
> +
>  static void spapr_machine_class_init(ObjectClass *oc, void *data)
>  {
>      MachineClass *mc = MACHINE_CLASS(oc);
> @@ -4358,6 +4397,8 @@ static void spapr_machine_class_init(ObjectClass *oc, void *data)
>      vhc->hpte_set_r = spapr_hpte_set_r;
>      vhc->get_pate = spapr_get_pate;
>      vhc->encode_hpt_for_kvm_pr = spapr_encode_hpt_for_kvm_pr;
> +    vhc->cpu_exec_enter = spapr_cpu_exec_enter;
> +    vhc->cpu_exec_exit = spapr_cpu_exec_exit;
>      xic->ics_get = spapr_ics_get;
>      xic->ics_resend = spapr_ics_resend;
>      xic->icp_get = spapr_icp_get;
> diff --git a/hw/ppc/spapr_cpu_core.c b/hw/ppc/spapr_cpu_core.c
> index 5621fb9a3d..54abf5308c 100644
> --- a/hw/ppc/spapr_cpu_core.c
> +++ b/hw/ppc/spapr_cpu_core.c
> @@ -261,6 +261,7 @@ error:
>  static PowerPCCPU *spapr_create_vcpu(SpaprCpuCore *sc, int i, Error **errp)
>  {
>      SpaprCpuCoreClass *scc = SPAPR_CPU_CORE_GET_CLASS(sc);
> +    SpaprCpuState *spapr_cpu;
>      CPUCore *cc = CPU_CORE(sc);
>      Object *obj;
>      char *id;
> @@ -287,7 +288,8 @@ static PowerPCCPU *spapr_create_vcpu(SpaprCpuCore *sc, int i, Error **errp)
>          goto err;
>      }
>  
> -    cpu->machine_data = g_new0(SpaprCpuState, 1);
> +    spapr_cpu = g_new0(SpaprCpuState, 1);
> +    cpu->machine_data = spapr_cpu;
>  
>      object_unref(obj);
>      return cpu;
> diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c
> index 6808d4cda8..e615881ac4 100644
> --- a/hw/ppc/spapr_hcall.c
> +++ b/hw/ppc/spapr_hcall.c
> @@ -874,11 +874,6 @@ unmap_out:
>  #define FLAGS_DEREGISTER_DTL       0x0000c00000000000ULL
>  #define FLAGS_DEREGISTER_SLBSHADOW 0x0000e00000000000ULL
>  
> -#define VPA_MIN_SIZE           640
> -#define VPA_SIZE_OFFSET        0x4
> -#define VPA_SHARED_PROC_OFFSET 0x9
> -#define VPA_SHARED_PROC_VAL    0x2
> -
>  static target_ulong register_vpa(PowerPCCPU *cpu, target_ulong vpa)
>  {
>      CPUState *cs = CPU(cpu);
> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> index 60553d32c4..5d36eec9d0 100644
> --- a/include/hw/ppc/spapr.h
> +++ b/include/hw/ppc/spapr.h
> @@ -525,6 +525,13 @@ void spapr_register_hypercall(target_ulong opcode, spapr_hcall_fn fn);
>  target_ulong spapr_hypercall(PowerPCCPU *cpu, target_ulong opcode,
>                               target_ulong *args);
>  
> +/* Virtual Processor Area structure constants */
> +#define VPA_MIN_SIZE           640
> +#define VPA_SIZE_OFFSET        0x4
> +#define VPA_SHARED_PROC_OFFSET 0x9
> +#define VPA_SHARED_PROC_VAL    0x2
> +#define VPA_DISPATCH_COUNTER   0x100
> +
>  /* ibm,set-eeh-option */
>  #define RTAS_EEH_DISABLE                 0
>  #define RTAS_EEH_ENABLE                  1
> diff --git a/include/hw/ppc/spapr_cpu_core.h b/include/hw/ppc/spapr_cpu_core.h
> index f9645a7290..a40cd08ea0 100644
> --- a/include/hw/ppc/spapr_cpu_core.h
> +++ b/include/hw/ppc/spapr_cpu_core.h
> @@ -46,6 +46,7 @@ typedef struct SpaprCpuState {
>      uint64_t vpa_addr;
>      uint64_t slb_shadow_addr, slb_shadow_size;
>      uint64_t dtl_addr, dtl_size;
> +    bool prod; /* not migrated, only used to improve dispatch latencies */
>      struct ICPState *icp;
>      struct XiveTCTX *tctx;
>  } SpaprCpuState;
> diff --git a/target/ppc/cpu.h b/target/ppc/cpu.h
> index c9beba2a5c..78d6504acb 100644
> --- a/target/ppc/cpu.h
> +++ b/target/ppc/cpu.h
> @@ -1224,6 +1224,8 @@ struct PPCVirtualHypervisorClass {
>      void (*hpte_set_r)(PPCVirtualHypervisor *vhyp, hwaddr ptex, uint64_t pte1);
>      void (*get_pate)(PPCVirtualHypervisor *vhyp, ppc_v3_pate_t *entry);
>      target_ulong (*encode_hpt_for_kvm_pr)(PPCVirtualHypervisor *vhyp);
> +    void (*cpu_exec_enter)(PPCVirtualHypervisor *vhyp, PowerPCCPU *cpu);
> +    void (*cpu_exec_exit)(PPCVirtualHypervisor *vhyp, PowerPCCPU *cpu);
>  };
>  
>  #define TYPE_PPC_VIRTUAL_HYPERVISOR "ppc-virtual-hypervisor"
> diff --git a/target/ppc/translate_init.inc.c b/target/ppc/translate_init.inc.c
> index 86fc8f2e31..58d4a93b23 100644
> --- a/target/ppc/translate_init.inc.c
> +++ b/target/ppc/translate_init.inc.c
> @@ -10473,6 +10473,28 @@ static bool ppc_cpu_is_big_endian(CPUState *cs)
>  }
>  #endif
>  
> +static void ppc_cpu_exec_enter(CPUState *cs)
> +{
> +    PowerPCCPU *cpu = POWERPC_CPU(cs);
> +
> +    if (cpu->vhyp) {
> +        PPCVirtualHypervisorClass *vhc =
> +            PPC_VIRTUAL_HYPERVISOR_GET_CLASS(cpu->vhyp);
> +        vhc->cpu_exec_enter(cpu->vhyp, cpu);
> +    }
> +}
> +
> +static void ppc_cpu_exec_exit(CPUState *cs)
> +{
> +    PowerPCCPU *cpu = POWERPC_CPU(cs);
> +
> +    if (cpu->vhyp) {
> +        PPCVirtualHypervisorClass *vhc =
> +            PPC_VIRTUAL_HYPERVISOR_GET_CLASS(cpu->vhyp);
> +        vhc->cpu_exec_exit(cpu->vhyp, cpu);
> +    }
> +}
> +
>  static void ppc_cpu_instance_init(Object *obj)
>  {
>      PowerPCCPU *cpu = POWERPC_CPU(obj);
> @@ -10624,6 +10646,9 @@ static void ppc_cpu_class_init(ObjectClass *oc, void *data)
>      cc->tcg_initialize = ppc_translate_init;
>      cc->tlb_fill = ppc_cpu_tlb_fill;
>  #endif
> +    cc->cpu_exec_enter = ppc_cpu_exec_enter;
> +    cc->cpu_exec_exit = ppc_cpu_exec_exit;
> +
>      cc->disas_set_info = ppc_disas_set_info;
>  
>      dc->fw_name = "PowerPC,UNKNOWN";
>