Re: [PATCH v5 21/22] target/arm: Add mmu indexes for tag memory

[Richard Henderson]

On 12/6/19 3:46 AM, Peter Maydell wrote:
>> +    case ARMMMUIdx_TagS:
>> +    case ARMMMUIdx_TagNS:
>> +        /* Indicate tag memory to arm_asidx_from_attrs.  */
>> +        attrs->target_tlb_bit2 = true;
>> +        break;
> 
> So here we fall through to the "handle a stage 1 lookup" code, which:
>  * sets attrs->secure
>  * sets attrs->user (always false, so we could have left it alone)
>  * skips the FCSE handling (as we're v8)
>  * skips the PMSA handling
>  * hits the regime_translation_disabled() check, which fills in
>    *phys_ptr, *prot and *page_size and returns

Exactly.

> Maybe it would be clearer if this case here just did all of that:
> 
>     case ARMMMUIdx_TagS:
>         attrs->secure = true;
>         /* fall through */
>     case ARMMMUIdx_TagNS:
>         /* Indicate tag memory to arm_asidx_from_attrs.  */
>         attrs->target_tlb_bit2 = true;
>         *phys_ptr = address;
>         *prot = PAGE_READ | PAGE_WRITE | PAGE_EXEC;
>         *page_size = TARGET_PAGE_SIZE;
>         return 0;
> 
> Did I miss anything out?

I think that's about it.  I thought about doing exactly this.

Also, this is a better location if I ever do something about the TODO in tne
next patch, wherein I talk about mapping not from physical address but from the
normal ram's ramaddr_t, so as to
cache that mapping step as well.


r~