Re: [Qemu-devel] [PATCHv3 2/4] pseries: Move CPU compatibility property to machine

[Greg Kurz <groug@kaod.org>]

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On Thu, 27 Apr 2017 17:28:41 +1000
David Gibson <david@gibson.dropbear.id.au> wrote:

> Server class POWER CPUs have a "compat" property, which is used to set the
> backwards compatibility mode for the processor.  However, this only makes
> sense for machine types which don't give the guest access to hypervisor
> privilege - otherwise the compatibility level is under the guest's control.
> 
> To reflect this, this removes the CPU 'compat' property and instead
> creates a 'max-cpu-compat' property on the pseries machine.  Strictly
> speaking this breaks compatibility, but AFAIK the 'compat' option was
> never (directly) used with -device or device_add.
> 
> The option was used with -cpu.  So, to maintain compatibility, this patch
> adds a hack to the cpu option parsing to strip out any compat options
> supplied with -cpu and set them on the machine property instead of the new
> removed cpu property.
> 
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> ---
>  hw/ppc/spapr.c              |  6 +++-
>  hw/ppc/spapr_cpu_core.c     | 41 ++++++++++++++++++++--
>  hw/ppc/spapr_hcall.c        |  2 +-
>  include/hw/ppc/spapr.h      | 12 ++++---
>  target/ppc/compat.c         | 65 +++++++++++++++++++++++++++++++++++
>  target/ppc/cpu.h            |  6 ++--
>  target/ppc/translate_init.c | 84 +++++++++++++--------------------------------
>  7 files changed, 145 insertions(+), 71 deletions(-)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 80d12d0..547fa27 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -2117,7 +2117,7 @@ static void ppc_spapr_init(MachineState *machine)
>          machine->cpu_model = kvm_enabled() ? "host" : smc->tcg_default_cpu;
>      }
>  
> -    ppc_cpu_parse_features(machine->cpu_model);
> +    spapr_cpu_parse_features(spapr);
>  
>      spapr_init_cpus(spapr);
>  
> @@ -2480,6 +2480,10 @@ static void spapr_machine_initfn(Object *obj)
>                                      " place of standard EPOW events when possible"
>                                      " (required for memory hot-unplug support)",
>                                      NULL);
> +
> +    object_property_add(obj, "max-cpu-compat", "str",
> +                        ppc_compat_prop_get, ppc_compat_prop_set,
> +                        NULL, &spapr->max_compat_pvr, &error_fatal);
>  }
>  
>  static void spapr_machine_finalizefn(Object *obj)
> diff --git a/hw/ppc/spapr_cpu_core.c b/hw/ppc/spapr_cpu_core.c
> index 4389ef4..ba610bc 100644
> --- a/hw/ppc/spapr_cpu_core.c
> +++ b/hw/ppc/spapr_cpu_core.c
> @@ -20,6 +20,43 @@
>  #include "sysemu/numa.h"
>  #include "qemu/error-report.h"
>  
> +void spapr_cpu_parse_features(sPAPRMachineState *spapr)
> +{
> +    /*
> +     * Backwards compatibility hack:
> +
> +     *   CPUs had a "compat=" property which didn't make sense for
> +     *   anything except pseries.  It was replaced by "max-cpu-compat"
> +     *   machine option.  This supports old command lines like
> +     *       -cpu POWER8,compat=power7
> +     *   By stripping the compat option and applying it to the machine
> +     *   before passing it on to the cpu level parser.
> +     */
> +    gchar **inpieces;
> +    int n, i;
> +    gchar *compat_str = NULL;
> +
> +    inpieces = g_strsplit(MACHINE(spapr)->cpu_model, ",", 0);
> +    n = g_strv_length(inpieces);
> +
> +    /* inpieces[0] is the actual model string */
> +    for (i = 0; i < n; i++) {
> +        if (g_str_has_prefix(inpieces[i], "compat=")) {
> +            compat_str = inpieces[i];
> +        }
> +    }
> +
> +    if (compat_str) {
> +        char *val = compat_str + strlen("compat=");
> +        object_property_set_str(OBJECT(spapr), val, "max-cpu-compat",
> +                                &error_fatal);
> +    }
> +
> +    ppc_cpu_parse_features(MACHINE(spapr)->cpu_model);
> +
> +    g_strfreev(inpieces);
> +}
> +
>  static void spapr_cpu_reset(void *opaque)
>  {
>      sPAPRMachineState *spapr = SPAPR_MACHINE(qdev_get_machine());
> @@ -70,10 +107,10 @@ static void spapr_cpu_init(sPAPRMachineState *spapr, PowerPCCPU *cpu,
>      /* Enable PAPR mode in TCG or KVM */
>      cpu_ppc_set_papr(cpu, PPC_VIRTUAL_HYPERVISOR(spapr));
>  
> -    if (cpu->max_compat) {
> +    if (spapr->max_compat_pvr) {
>          Error *local_err = NULL;
>  
> -        ppc_set_compat(cpu, cpu->max_compat, &local_err);
> +        ppc_set_compat(cpu, spapr->max_compat_pvr, &local_err);
>          if (local_err) {
>              error_propagate(errp, local_err);
>              return;
> diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c
> index 9f18f75..d4dc12b 100644
> --- a/hw/ppc/spapr_hcall.c
> +++ b/hw/ppc/spapr_hcall.c
> @@ -1059,7 +1059,7 @@ static target_ulong h_client_architecture_support(PowerPCCPU *cpu,
>      target_ulong list = ppc64_phys_to_real(args[0]);
>      target_ulong ov_table;
>      bool explicit_match = false; /* Matched the CPU's real PVR */
> -    uint32_t max_compat = cpu->max_compat;
> +    uint32_t max_compat = spapr->max_compat_pvr;
>      uint32_t best_compat = 0;
>      int i;
>      sPAPROptionVector *ov1_guest, *ov5_guest, *ov5_cas_old, *ov5_updates;
> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> index 5802f88..40d5f89 100644
> --- a/include/hw/ppc/spapr.h
> +++ b/include/hw/ppc/spapr.h
> @@ -86,16 +86,19 @@ struct sPAPRMachineState {
>      uint64_t rtc_offset; /* Now used only during incoming migration */
>      struct PPCTimebase tb;
>      bool has_graphics;
> -    sPAPROptionVector *ov5;         /* QEMU-supported option vectors */
> -    sPAPROptionVector *ov5_cas;     /* negotiated (via CAS) option vectors */
> -    bool cas_reboot;
> -    bool cas_legacy_guest_workaround;
>  
>      Notifier epow_notifier;
>      QTAILQ_HEAD(, sPAPREventLogEntry) pending_events;
>      bool use_hotplug_event_source;
>      sPAPREventSource *event_sources;
>  
> +    /* ibm,client-architecture-support option negotiation */
> +    bool cas_reboot;
> +    bool cas_legacy_guest_workaround;
> +    sPAPROptionVector *ov5;         /* QEMU-supported option vectors */
> +    sPAPROptionVector *ov5_cas;     /* negotiated (via CAS) option vectors */
> +    uint32_t max_compat_pvr;
> +
>      /* Migration state */
>      int htab_save_index;
>      bool htab_first_pass;
> @@ -633,6 +636,7 @@ void spapr_hotplug_req_add_by_count_indexed(sPAPRDRConnectorType drc_type,
>                                              uint32_t count, uint32_t index);
>  void spapr_hotplug_req_remove_by_count_indexed(sPAPRDRConnectorType drc_type,
>                                                 uint32_t count, uint32_t index);
> +void spapr_cpu_parse_features(sPAPRMachineState *spapr);
>  void *spapr_populate_hotplug_cpu_dt(CPUState *cs, int *fdt_offset,
>                                      sPAPRMachineState *spapr);
>  
> diff --git a/target/ppc/compat.c b/target/ppc/compat.c
> index e8ec1e1..476dead 100644
> --- a/target/ppc/compat.c
> +++ b/target/ppc/compat.c
> @@ -24,9 +24,11 @@
>  #include "sysemu/cpus.h"
>  #include "qemu/error-report.h"
>  #include "qapi/error.h"
> +#include "qapi/visitor.h"
>  #include "cpu-models.h"
>  
>  typedef struct {
> +    const char *name;
>      uint32_t pvr;
>      uint64_t pcr;
>      uint64_t pcr_level;
> @@ -38,6 +40,7 @@ static const CompatInfo compat_table[] = {
>       * Ordered from oldest to newest - the code relies on this
>       */
>      { /* POWER6, ISA2.05 */
> +        .name = "power6",
>          .pvr = CPU_POWERPC_LOGICAL_2_05,
>          .pcr = PCR_COMPAT_3_00 | PCR_COMPAT_2_07 | PCR_COMPAT_2_06 |
>                 PCR_COMPAT_2_05 | PCR_TM_DIS | PCR_VSX_DIS,
> @@ -45,18 +48,21 @@ static const CompatInfo compat_table[] = {
>          .max_threads = 2,
>      },
>      { /* POWER7, ISA2.06 */
> +        .name = "power7",
>          .pvr = CPU_POWERPC_LOGICAL_2_06,
>          .pcr = PCR_COMPAT_3_00 | PCR_COMPAT_2_07 | PCR_COMPAT_2_06 | PCR_TM_DIS,
>          .pcr_level = PCR_COMPAT_2_06,
>          .max_threads = 4,
>      },
>      {
> +        .name = "power7+",
>          .pvr = CPU_POWERPC_LOGICAL_2_06_PLUS,
>          .pcr = PCR_COMPAT_3_00 | PCR_COMPAT_2_07 | PCR_COMPAT_2_06 | PCR_TM_DIS,
>          .pcr_level = PCR_COMPAT_2_06,
>          .max_threads = 4,
>      },
>      { /* POWER8, ISA2.07 */
> +        .name = "power8",
>          .pvr = CPU_POWERPC_LOGICAL_2_07,
>          .pcr = PCR_COMPAT_3_00 | PCR_COMPAT_2_07,
>          .pcr_level = PCR_COMPAT_2_07,

And now we also have POWER9 in the list, so:

         .max_threads = 8,
     },
     { /* POWER9, ISA3.00 */
+        .name = "power9",
         .pvr = CPU_POWERPC_LOGICAL_3_00,
         .pcr = PCR_COMPAT_3_00,
         .pcr_level = PCR_COMPAT_3_00,

> @@ -189,3 +195,62 @@ int ppc_compat_max_threads(PowerPCCPU *cpu)
>  
>      return n_threads;
>  }
> +
> +void ppc_compat_prop_get(Object *obj, Visitor *v, const char *name,
> +                         void *opaque, Error **errp)
> +{
> +    uint32_t compat_pvr = *((uint32_t *)opaque);
> +    const char *value;
> +
> +    if (!compat_pvr) {
> +        value = "";
> +    } else {
> +        const CompatInfo *compat = compat_by_pvr(compat_pvr);
> +
> +        g_assert(compat);
> +
> +        value = compat->name;
> +    }
> +
> +    visit_type_str(v, name, (char **)&value, errp);
> +}
> +
> +void ppc_compat_prop_set(Object *obj, Visitor *v, const char *name,
> +                         void *opaque, Error **errp)
> +{
> +    Error *error = NULL;
> +    char *value;
> +    uint32_t compat_pvr;
> +
> +    visit_type_str(v, name, &value, &error);
> +    if (error) {
> +        error_propagate(errp, error);
> +        return;
> +    }
> +
> +    if (strcmp(value, "") == 0) {
> +        compat_pvr = 0;

The current implementation in powerpc_get_compat() considers "" to be an
invalid compatibility mode. Is there a reason to behave differently with
max-cpu-compat ?

> +    } else {
> +        int i;
> +        const CompatInfo *compat = NULL;
> +
> +        for (i = 0; i < ARRAY_SIZE(compat_table); i++) {
> +            if (strcmp(value, compat_table[i].name) == 0) {
> +                compat = &compat_table[i];
> +                break;
> +
> +            }
> +        }
> +
> +        if (!compat) {
> +            error_setg(errp, "Invalid compatibility mode \"%s\"", value);
> +            goto out;
> +        }
> +        compat_pvr = compat->pvr;
> +    }
> +
> +    *((uint32_t *)opaque) = compat_pvr;
> +
> +out:
> +    g_free(value);
> +}
> diff --git a/target/ppc/cpu.h b/target/ppc/cpu.h
> index e0ff041..e953e75 100644
> --- a/target/ppc/cpu.h
> +++ b/target/ppc/cpu.h
> @@ -1185,7 +1185,6 @@ typedef struct PPCVirtualHypervisorClass PPCVirtualHypervisorClass;
>   * PowerPCCPU:
>   * @env: #CPUPPCState
>   * @cpu_dt_id: CPU index used in the device tree. KVM uses this index too
> - * @max_compat: Maximal supported logical PVR from the command line
>   * @compat_pvr: Current logical PVR, zero if in "raw" mode
>   *
>   * A PowerPC CPU.
> @@ -1197,7 +1196,6 @@ struct PowerPCCPU {
>  
>      CPUPPCState env;
>      int cpu_dt_id;
> -    uint32_t max_compat;
>      uint32_t compat_pvr;
>      PPCVirtualHypervisor *vhyp;
>      Object *intc;
> @@ -1369,6 +1367,10 @@ void ppc_set_compat(PowerPCCPU *cpu, uint32_t compat_pvr, Error **errp);
>  void ppc_set_compat_all(uint32_t compat_pvr, Error **errp);
>  #endif
>  int ppc_compat_max_threads(PowerPCCPU *cpu);
> +void ppc_compat_prop_get(Object *obj, Visitor *v,
> +                         const char *name, void *opaque, Error **err);
> +void ppc_compat_prop_set(Object *obj, Visitor *v,
> +                         const char *name, void *opaque, Error **err);
>  #endif /* defined(TARGET_PPC64) */
>  
>  #include "exec/cpu-all.h"
> diff --git a/target/ppc/translate_init.c b/target/ppc/translate_init.c
> index e82e3e6..a92c825 100644
> --- a/target/ppc/translate_init.c
> +++ b/target/ppc/translate_init.c
> @@ -8413,73 +8413,35 @@ POWERPC_FAMILY(POWER5P)(ObjectClass *oc, void *data)
>      pcc->l1_icache_size = 0x10000;
>  }
>  
> -static void powerpc_get_compat(Object *obj, Visitor *v, const char *name,
> -                               void *opaque, Error **errp)
> -{
> -    char *value = (char *)"";
> -    Property *prop = opaque;
> -    uint32_t *max_compat = qdev_get_prop_ptr(DEVICE(obj), prop);
> -
> -    switch (*max_compat) {
> -    case CPU_POWERPC_LOGICAL_2_05:
> -        value = (char *)"power6";
> -        break;
> -    case CPU_POWERPC_LOGICAL_2_06:
> -        value = (char *)"power7";
> -        break;
> -    case CPU_POWERPC_LOGICAL_2_07:
> -        value = (char *)"power8";
> -        break;
> -    case 0:
> -        break;
> -    default:
> -        error_report("Internal error: compat is set to %x", *max_compat);
> -        abort();
> -        break;
> -    }
> -
> -    visit_type_str(v, name, &value, errp);
> -}
> -
> -static void powerpc_set_compat(Object *obj, Visitor *v, const char *name,
> -                               void *opaque, Error **errp)
> +/*
> + * The CPU used to have a "compat" property which set the
> + * compatibility mode PVR.  However, this was conceptually broken - it
> + * only makes sense on the pseries machine type (otherwise the guest
> + * owns the PCR and can control the compatibility mode itself).  It's
> + * been replaced with the 'max-cpu-compat' property on the pseries
> + * machine type.  For backwards compatibility, pseries specially
> + * parses the -cpu parameter and converts old compat= parameters into
> + * the appropriate machine parameters.  This stub implementation of
> + * the parameter catches any uses on explicitly created CPUs.
> + */
> +static void getset_compat_deprecated(Object *obj, Visitor *v, const char *name,
> +                                     void *opaque, Error **errp)
>  {
> -    Error *error = NULL;
> -    char *value = NULL;
> -    Property *prop = opaque;
> -    uint32_t *max_compat = qdev_get_prop_ptr(DEVICE(obj), prop);
> -
> -    visit_type_str(v, name, &value, &error);
> -    if (error) {
> -        error_propagate(errp, error);
> -        return;
> -    }
> -
> -    if (strcmp(value, "power6") == 0) {
> -        *max_compat = CPU_POWERPC_LOGICAL_2_05;
> -    } else if (strcmp(value, "power7") == 0) {
> -        *max_compat = CPU_POWERPC_LOGICAL_2_06;
> -    } else if (strcmp(value, "power8") == 0) {
> -        *max_compat = CPU_POWERPC_LOGICAL_2_07;
> -    } else {
> -        error_setg(errp, "Invalid compatibility mode \"%s\"", value);
> -    }
> -
> -    g_free(value);
> +    error_report("CPU 'compat' property is deprecated and has no effect; use max-cpu-compat machine property instead");
> +    visit_type_null(v, name, errp);
>  }
>  

As suggested in another mail, maybe NULL should be passed instead of errp if
we really want to implement the "has no effect". Otherwise, it has the effect
of terminating QEMU when passing a compat prop that isn't "".

> -static PropertyInfo powerpc_compat_propinfo = {
> +static PropertyInfo ppc_compat_deprecated_propinfo = {
>      .name = "str",
> -    .description = "compatibility mode, power6/power7/power8",
> -    .get = powerpc_get_compat,
> -    .set = powerpc_set_compat,
> +    .description = "compatibility mode (deprecated)",
> +    .get = getset_compat_deprecated,
> +    .set = getset_compat_deprecated,
>  };
> -
> -#define DEFINE_PROP_POWERPC_COMPAT(_n, _s, _f) \
> -    DEFINE_PROP(_n, _s, _f, powerpc_compat_propinfo, uint32_t)
> -
>  static Property powerpc_servercpu_properties[] = {
> -    DEFINE_PROP_POWERPC_COMPAT("compat", PowerPCCPU, max_compat),
> +    {
> +        .name = "compat",
> +        .info = &ppc_compat_deprecated_propinfo,
> +    },
>      DEFINE_PROP_END_OF_LIST(),
>  };
>  


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