Re: [Qemu-devel] [PATCH 4/9] target-ppc: Implement "compat" CPU option

[Alexey Kardashevskiy <aik@ozlabs.ru>]

On 05/21/2014 06:00 PM, Alexander Graf wrote:
> 
> On 21.05.14 09:59, Alexey Kardashevskiy wrote:
>> On 05/21/2014 05:29 PM, Alexander Graf wrote:
>>> On 21.05.14 08:57, Alexey Kardashevskiy wrote:
>>>> On 05/17/2014 06:47 AM, Alexander Graf wrote:
>>>>> On 16.05.14 17:17, Alexey Kardashevskiy wrote:
>>>>>> On 05/17/2014 12:05 AM, Alexander Graf wrote:
>>>>>>> On 15.05.14 13:28, Alexey Kardashevskiy wrote:
>>>>>>>> This adds basic support for the "compat" CPU option. By specifying
>>>>>>>> the compat property, the user can manually switch guest CPU mode from
>>>>>>>> "raw" to "architected".
>>>>>>>>
>>>>>>>> Since the actual compatibility mode is not implemented yet, this does
>>>>>>>> not change the existing behavior.
>>>>>>>>
>>>>>>>> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
>>>>>>>> ---
>>>>>>>>      hw/ppc/spapr.c              | 15 ++++++++++++++-
>>>>>>>>      target-ppc/cpu-models.h     |  6 ++++++
>>>>>>>>      target-ppc/cpu-qom.h        |  2 ++
>>>>>>>>      target-ppc/cpu.h            |  3 +++
>>>>>>>>      target-ppc/translate_init.c | 35
>>>>>>>> +++++++++++++++++++++++++++++++++++
>>>>>>>>      5 files changed, 60 insertions(+), 1 deletion(-)
>>>>>>>>
>>>>>>>> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
>>>>>>>> index 0f8bd95..61d0675 100644
>>>>>>>> --- a/hw/ppc/spapr.c
>>>>>>>> +++ b/hw/ppc/spapr.c
>>>>>>>> @@ -212,7 +212,8 @@ static int spapr_fixup_cpu_dt(void *fdt,
>>>>>>>> sPAPREnvironment *spapr)
>>>>>>>>            CPU_FOREACH(cpu) {
>>>>>>>>              DeviceClass *dc = DEVICE_GET_CLASS(cpu);
>>>>>>>> -        int index = ppc_get_vcpu_dt_id(POWERPC_CPU(cpu));
>>>>>>>> +        PowerPCCPU *pcpu = POWERPC_CPU(cpu);
>>>>>>>> +        int index = ppc_get_vcpu_dt_id(pcpu);
>>>>>>>>              uint32_t associativity[] = {cpu_to_be32(0x5),
>>>>>>>>                                          cpu_to_be32(0x0),
>>>>>>>>                                          cpu_to_be32(0x0),
>>>>>>>> @@ -249,6 +250,14 @@ static int spapr_fixup_cpu_dt(void *fdt,
>>>>>>>> sPAPREnvironment *spapr)
>>>>>>>>                  return ret;
>>>>>>>>              }
>>>>>>>>      +        if (pcpu->cpu_version) {
>>>>>>>> +            ret = fdt_setprop(fdt, offset, "cpu-version",
>>>>>>>> +                              &pcpu->cpu_version,
>>>>>>>> sizeof(pcpu->cpu_version));
>>>>>>>> +            if (ret < 0) {
>>>>>>>> +                return ret;
>>>>>>>> +            }
>>>>>>>> +        }
>>>>>>>> +
>>>>>>>>              /* Build interrupt servers and gservers properties */
>>>>>>>>              for (i = 0; i < smp_threads; i++) {
>>>>>>>>                  servers_prop[i] = cpu_to_be32(index + i);
>>>>>>>> @@ -1278,6 +1287,10 @@ static void ppc_spapr_init(QEMUMachineInitArgs
>>>>>>>> *args)
>>>>>>>>                  kvmppc_set_papr(cpu);
>>>>>>>>              }
>>>>>>>>      +        if (cpu->max_compat) {
>>>>>>>> +            ppc_set_compat(cpu, cpu->max_compat);
>>>>>>>> +        }
>>>>>>>> +
>>>>>>>>              xics_cpu_setup(spapr->icp, cpu);
>>>>>>>>                qemu_register_reset(spapr_cpu_reset, cpu);
>>>>>>>> diff --git a/target-ppc/cpu-models.h b/target-ppc/cpu-models.h
>>>>>>>> index 33d2c51..45c0028 100644
>>>>>>>> --- a/target-ppc/cpu-models.h
>>>>>>>> +++ b/target-ppc/cpu-models.h
>>>>>>>> @@ -753,4 +753,10 @@ enum {
>>>>>>>>          POWERPC_SVR_8641D              = 0x80900121,
>>>>>>>>      };
>>>>>>>>      +/* Processor Compatibility mask (PCR) */
>>>>>>>> +enum {
>>>>>>>> +    POWERPC_ISA_COMPAT_2_05 = 0x02,
>>>>>>>> +    POWERPC_ISA_COMPAT_2_06 = 0x04,
>>>>>>>> +};
>>>>>>>> +
>>>>>>>>      #endif
>>>>>>>> diff --git a/target-ppc/cpu-qom.h b/target-ppc/cpu-qom.h
>>>>>>>> index 2a8515b..dfd1419 100644
>>>>>>>> --- a/target-ppc/cpu-qom.h
>>>>>>>> +++ b/target-ppc/cpu-qom.h
>>>>>>>> @@ -83,6 +83,7 @@ typedef struct PowerPCCPUClass {
>>>>>>>>       * @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
>>>>>>>> + * @cpu_version: Current logical PVR, zero if in "raw" mode
>>>>>>>>       *
>>>>>>>>       * A PowerPC CPU.
>>>>>>>>       */
>>>>>>>> @@ -94,6 +95,7 @@ struct PowerPCCPU {
>>>>>>>>          CPUPPCState env;
>>>>>>>>          int cpu_dt_id;
>>>>>>>>          uint32_t max_compat;
>>>>>>>> +    uint32_t cpu_version;
>>>>>>>>      };
>>>>>>>>        static inline PowerPCCPU *ppc_env_get_cpu(CPUPPCState *env)
>>>>>>>> diff --git a/target-ppc/cpu.h b/target-ppc/cpu.h
>>>>>>>> index d498340..f61675a 100644
>>>>>>>> --- a/target-ppc/cpu.h
>>>>>>>> +++ b/target-ppc/cpu.h
>>>>>>>> @@ -1123,6 +1123,8 @@ void ppc_store_msr (CPUPPCState *env,
>>>>>>>> target_ulong
>>>>>>>> value);
>>>>>>>>        void ppc_cpu_list (FILE *f, fprintf_function cpu_fprintf);
>>>>>>>>      +void ppc_set_compat(PowerPCCPU *cpu, uint32_t cpu_version);
>>>>>>>> +
>>>>>>>>      /* Time-base and decrementer management */
>>>>>>>>      #ifndef NO_CPU_IO_DEFS
>>>>>>>>      uint64_t cpu_ppc_load_tbl (CPUPPCState *env);
>>>>>>>> @@ -1338,6 +1340,7 @@ static inline int cpu_mmu_index (CPUPPCState
>>>>>>>> *env)
>>>>>>>>      #define SPR_LPCR              (0x13E)
>>>>>>>>      #define SPR_BOOKE_DVC2        (0x13F)
>>>>>>>>      #define SPR_BOOKE_TSR         (0x150)
>>>>>>>> +#define SPR_PCR               (0x152)
>>>>>>>>      #define SPR_BOOKE_TCR         (0x154)
>>>>>>>>      #define SPR_BOOKE_TLB0PS      (0x158)
>>>>>>>>      #define SPR_BOOKE_TLB1PS      (0x159)
>>>>>>>> diff --git a/target-ppc/translate_init.c b/target-ppc/translate_init.c
>>>>>>>> index 6f61b34..c4bd5de 100644
>>>>>>>> --- a/target-ppc/translate_init.c
>>>>>>>> +++ b/target-ppc/translate_init.c
>>>>>>>> @@ -7803,6 +7803,15 @@ static void init_proc_POWER7 (CPUPPCState *env)
>>>>>>>>          /* Can't find information on what this should be on
>>>>>>>> reset.  This
>>>>>>>>           * value is the one used by 74xx processors. */
>>>>>>>>          vscr_init(env, 0x00010000);
>>>>>>>> +
>>>>>>>> +    /*
>>>>>>>> +     * Register PCR to report POWERPC_EXCP_PRIV_REG instead of
>>>>>>>> +     * POWERPC_EXCP_INVAL_SPR.
>>>>>>>> +     */
>>>>>>>> +    spr_register(env, SPR_PCR, "PCR",
>>>>>>>> +                 SPR_NOACCESS, SPR_NOACCESS,
>>>>>>>> +                 SPR_NOACCESS, SPR_NOACCESS,
>>>>>>>> +                 0x00000000);
>>>>>>>>      }
>>>>>>>>        POWERPC_FAMILY(POWER7)(ObjectClass *oc, void *data)
>>>>>>>> @@ -8880,6 +8889,32 @@ static void ppc_cpu_unrealizefn(DeviceState
>>>>>>>> *dev,
>>>>>>>> Error **errp)
>>>>>>>>          }
>>>>>>>>      }
>>>>>>>>      +void ppc_set_compat(PowerPCCPU *cpu, uint32_t cpu_version)
>>>>>>>> +{
>>>>>>>> +    CPUPPCState *env = &cpu->env;
>>>>>>>> +
>>>>>>>> +    cpu->cpu_version = cpu_version;
>>>>>>>> +
>>>>>>>> +    /*
>>>>>>>> +     * Calculate PCR value from virtual PVR.
>>>>>>>> +     * TODO: support actual compatibility in TCG.
>>>>>>>> +     */
>>>>>>>> +    switch (cpu_version) {
>>>>>>>> +    case CPU_POWERPC_LOGICAL_2_05:
>>>>>>>> +        env->spr[SPR_PCR] = POWERPC_ISA_COMPAT_2_05;
>>>>>>>> +        break;
>>>>>>>> +    case CPU_POWERPC_LOGICAL_2_06:
>>>>>>>> +        env->spr[SPR_PCR] = POWERPC_ISA_COMPAT_2_06;
>>>>>>>> +        break;
>>>>>>>> +    case CPU_POWERPC_LOGICAL_2_06_PLUS:
>>>>>>>> +        env->spr[SPR_PCR] = POWERPC_ISA_COMPAT_2_06;
>>>>>>>> +        break;
>>>>>>> Don't we have to disable all those fancy p8 features too?
>>>>>>>
>>>>>>> #define   PCR_VEC_DIS   (1ul << (63-0)) /* Vec. disable (bit NA since
>>>>>>> POWER8) */
>>>>>>> #define   PCR_VSX_DIS   (1ul << (63-1)) /* VSX disable (bit NA since
>>>>>>> POWER8) */
>>>>>>> #define   PCR_TM_DIS    (1ul << (63-2)) /* Trans. memory disable
>>>>>>> (POWER8) */
>>>>>> Yep, makes sense to set "TM" for POWER < 8 and VSX+VEC for POWER < 7.
>>>>>>
>>>>>>> In fact, we probably want those bits always set when compat < power8.
>>>>>> Why? VSX is present on power7. VEC is defined in 2.06 too.
>>>>> True. So how does pre-p8 treat those p8 and above bits?
>>>> PowerISA 2.07 says if 2.06 mode is selected, the TM bit does not matter
>>>> anymore - TM will be disabled because 2.06 does not define it at all. The
>>>> same is true for VSX and 2.05 mode. So just setting a mode must be ok.
>>> And for POWER8-on-POWER9 (or whatever it will be called) we can just set
>>> PCR to the respective feature disable bits. I think that should work.
>> I lost you here. I suspect it will also have "2.07" compatibility mode and
>> we will use that instead of disabling feature one by one.
> 
> Considering that the architects added by-feature bits, I would assume they
> won't introduce a 2.07 bit but rather make every new feature disableable
> one by one. 

2.05 defines PCR_VEC_DIS already and since then 2 specs were released so it
is unlikely to happen :)


> But maybe I'm wrong - the point is that either way will work
> and is future proof ;).



-- 
Alexey