Re: [PATCH v4 02/17] target/ppc: Move 601 hflags adjustment to hreg_compute_hflags

["Cédric Le Goater" <clg@kaod.org>]

On 3/15/21 7:46 PM, Richard Henderson wrote:
> Keep all hflags computation in one place, as this will be
> especially important later.
> 
> Introduce a new POWERPC_FLAG_HID0_LE bit to indicate when
> LE should be taken from HID0.  This appears to be set if
> and only if POWERPC_FLAG_RTC_CLK is set, but we're not
> short of bits and having both names will avoid confusion.
> 
> Note that this was the only user of hflags_nmsr, so we can
> perform a straight assignment rather than mask and set.
> 
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

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

Thanks,

C.
> ---
>  target/ppc/cpu.h                |  2 ++
>  target/ppc/helper_regs.c        | 13 +++++++++++--
>  target/ppc/misc_helper.c        |  8 +++-----
>  target/ppc/translate_init.c.inc |  4 ++--
>  4 files changed, 18 insertions(+), 9 deletions(-)
> 
> diff --git a/target/ppc/cpu.h b/target/ppc/cpu.h
> index e73416da68..061d2eed1b 100644
> --- a/target/ppc/cpu.h
> +++ b/target/ppc/cpu.h
> @@ -581,6 +581,8 @@ enum {
>      POWERPC_FLAG_TM       = 0x00100000,
>      /* Has SCV (ISA 3.00)                                                    */
>      POWERPC_FLAG_SCV      = 0x00200000,
> +    /* Has HID0 for LE bit (601)                                             */
> +    POWERPC_FLAG_HID0_LE  = 0x00400000,
>  };
>  
>  /*****************************************************************************/
> diff --git a/target/ppc/helper_regs.c b/target/ppc/helper_regs.c
> index 5e18232b84..95b9aca61f 100644
> --- a/target/ppc/helper_regs.c
> +++ b/target/ppc/helper_regs.c
> @@ -96,8 +96,17 @@ void hreg_compute_hflags(CPUPPCState *env)
>      hflags_mask |= (1ULL << MSR_CM) | (1ULL << MSR_SF) | MSR_HVB;
>      hreg_compute_mem_idx(env);
>      env->hflags = env->msr & hflags_mask;
> -    /* Merge with hflags coming from other registers */
> -    env->hflags |= env->hflags_nmsr;
> +
> +    if (env->flags & POWERPC_FLAG_HID0_LE) {
> +        /*
> +         * Note that MSR_LE is not set in env->msr_mask for this cpu,
> +         * and so will never be set in msr or hflags at this point.
> +         */
> +        uint32_t le = extract32(env->spr[SPR_HID0], 3, 1);
> +        env->hflags |= le << MSR_LE;
> +        /* Retain for backward compatibility with migration. */
> +        env->hflags_nmsr = le << MSR_LE;
> +    }
>  }
>  
>  void cpu_interrupt_exittb(CPUState *cs)
> diff --git a/target/ppc/misc_helper.c b/target/ppc/misc_helper.c
> index 5d6e0de396..63e3147eb4 100644
> --- a/target/ppc/misc_helper.c
> +++ b/target/ppc/misc_helper.c
> @@ -194,16 +194,14 @@ void helper_store_hid0_601(CPUPPCState *env, target_ulong val)
>      target_ulong hid0;
>  
>      hid0 = env->spr[SPR_HID0];
> +    env->spr[SPR_HID0] = (uint32_t)val;
> +
>      if ((val ^ hid0) & 0x00000008) {
>          /* Change current endianness */
> -        env->hflags &= ~(1 << MSR_LE);
> -        env->hflags_nmsr &= ~(1 << MSR_LE);
> -        env->hflags_nmsr |= (1 << MSR_LE) & (((val >> 3) & 1) << MSR_LE);
> -        env->hflags |= env->hflags_nmsr;
> +        hreg_compute_hflags(env);
>          qemu_log("%s: set endianness to %c => " TARGET_FMT_lx "\n", __func__,
>                   val & 0x8 ? 'l' : 'b', env->hflags);
>      }
> -    env->spr[SPR_HID0] = (uint32_t)val;
>  }
>  
>  void helper_store_403_pbr(CPUPPCState *env, uint32_t num, target_ulong value)
> diff --git a/target/ppc/translate_init.c.inc b/target/ppc/translate_init.c.inc
> index c03a7c4f52..049d76cfd1 100644
> --- a/target/ppc/translate_init.c.inc
> +++ b/target/ppc/translate_init.c.inc
> @@ -5441,7 +5441,7 @@ POWERPC_FAMILY(601)(ObjectClass *oc, void *data)
>      pcc->excp_model = POWERPC_EXCP_601;
>      pcc->bus_model = PPC_FLAGS_INPUT_6xx;
>      pcc->bfd_mach = bfd_mach_ppc_601;
> -    pcc->flags = POWERPC_FLAG_SE | POWERPC_FLAG_RTC_CLK;
> +    pcc->flags = POWERPC_FLAG_SE | POWERPC_FLAG_RTC_CLK | POWERPC_FLAG_HID0_LE;
>  }
>  
>  #define POWERPC_MSRR_601v    (0x0000000000001040ULL)
> @@ -5485,7 +5485,7 @@ POWERPC_FAMILY(601v)(ObjectClass *oc, void *data)
>  #endif
>      pcc->bus_model = PPC_FLAGS_INPUT_6xx;
>      pcc->bfd_mach = bfd_mach_ppc_601;
> -    pcc->flags = POWERPC_FLAG_SE | POWERPC_FLAG_RTC_CLK;
> +    pcc->flags = POWERPC_FLAG_SE | POWERPC_FLAG_RTC_CLK | POWERPC_FLAG_HID0_LE;
>  }
>  
>  static void init_proc_602(CPUPPCState *env)
>