Re: [Qemu-devel] [[PATCH] 5/7] target-arm: Add TTBR regime function and use

[Peter Maydell]

On 27 March 2015 at 19:10, Greg Bellows <address@hidden> wrote:
> Add a utility function for choosing the correct TTBR system register based on
> the specified MMU index. Add use of function on physical address lookup.

> @@ -5376,20 +5390,26 @@ static int get_phys_addr_lpae(CPUARMState *env, 
> target_ulong address,
>      int32_t tbi = 0;
>      TCR *tcr = regime_tcr(env, mmu_idx);
>      int ap, ns, xn, pxn;
> +    uint32_t el = regime_el(env, mmu_idx);
>
>      /* TODO:
>       * This code assumes we're either a 64-bit EL1 or a 32-bit PL1;
> -     * it doesn't handle the different format TCR for TCR_EL2, TCR_EL3,
> -     * and VTCR_EL2, or the fact that those regimes don't have a split
> +     * it doesn't handle the different format TCR for and VTCR_EL2,
> +     * or the fact that those regimes don't have a split
>       * TTBR0/TTBR1. Attribute and permission bit handling should also
>       * be checked when adding support for those page table walks.
>       */
> -    if (arm_el_is_aa64(env, regime_el(env, mmu_idx))) {
> +    if (arm_el_is_aa64(env, el)) {
>          va_size = 64;
> -        if (extract64(address, 55, 1))
> -            tbi = extract64(tcr->raw_tcr, 38, 1);
> -        else
> -            tbi = extract64(tcr->raw_tcr, 37, 1);
> +        if (el == 3 || el == 2) {
> +            tbi = extract64(tcr->raw_tcr, 20, 1);
> +        } else {
> +            if (extract64(address, 55, 1)) {
> +                tbi = extract64(tcr->raw_tcr, 38, 1);
> +            } else {
> +                tbi = extract64(tcr->raw_tcr, 37, 1);
> +            }
> +        }
>          tbi *= 8;
>      }

The TTBR related parts of this patch are fine, but this section
feels a bit incomplete. The location of the TBI bit is not the
only thing about the TCR format that's different for TCR_EL2
and TCR_EL3. I think it would be better to move this hunk into
a separate patch that also fixes the other points the TODO comment
mentions (including the other parts of the function that access
raw_tcr bitfields).

-- PMM