Re: [Qemu-devel] [PATCH 8/8] PPC: Add e5500 CPU target

[Scott Wood <scottwood@freescale.com>]

On 06/20/2012 03:11 PM, Alexander Graf wrote:
> +    /* XXX better abstract into Emb.xxx features */
> +    if (version == fsl_e5500) {
> +        spr_register(env, SPR_BOOKE_EPCR, "EPCR",
> +                     SPR_NOACCESS, SPR_NOACCESS,
> +                     &spr_read_generic, &spr_write_generic,
> +                     0x00000000);
> +        spr_register(env, SPR_BOOKE_MAS7_MAS3, "MAS7_MAS3",
> +                     SPR_NOACCESS, SPR_NOACCESS,
> +                     &spr_read_mas73, &spr_write_mas73,
> +                     0x00000000);
> +        env->reset_msr = (1ULL < MSR_CM);

That's a funny way of writing "env->reset_msr = 0". :-)

Assuming you really meant "env->reset_msr = 1ULL << MSR_CM", why?  We
enter the kernel in 32-bit mode.  It resets in 32-bit mode as well, if
we ever implement that for e5500 QEMU.

You have the same issue in the previous patch with "1ULL < MSR_SF",
though I don't know if those chips actually do reset into 64-bit mode.

> +    }
>  
>  #if !defined(CONFIG_USER_ONLY)
>      env->nb_tlb = 0;
> @@ -4576,6 +4655,14 @@ static void init_proc_e500 (CPUPPCState *env, int version)
>  #endif
>  
>      init_excp_e200(env);
> +
> +#if !defined(CONFIG_USER_ONLY)
> +    /* We support 64bit wide IVPR on 64bit platforms */
> +    if (version == fsl_e5500) {
> +        env->ivpr_mask = (target_ulong)~0xFFFFULL;
> +    }
> +#endif

So, I'm guessing you don't do this unconditionally because QEMU will
generate 64-bit code if compiled that way, regardless of the actual
target -- and you don't want stray garbage in the upper 32 bits being
written into IVPR.  But why isn't this an issue with all the other SPRs?
 Why don't we have a problem with junk being written into the upper half
of MAS3, for example (there's MAS3_RPN_MASK, but it's not used)?

Speaking of which, I don't see where you change MAS2_EPN_MASK to take
MSR_CM into account (or to accept 64-bit MAS2 at all).

-Scott