Re: [Qemu-devel] Minor MMU fixes for PowerPC 40x emulation

[Alexander Graf]

On 02.10.2010, at 07:38, John Clark wrote:

> Hello,
> 
> I found I had to make a few minor changes to the MMU code for the
> PowerPC 40x emulation to get NetBSD to run on a virtual PowerPC 405
> core with qemu-system-ppcemb. The 'tlbre' instruction was not working,
> and permission checking for a TLB entry was not as strict as it should
> be. Diffs are included below.
> 
> Thank you.
> 
> - John Clark
> 
> diff --git a/target-ppc/helper.c b/target-ppc/helper.c
> index 3bc8a34..a8c1802 100644
> --- a/target-ppc/helper.c
> +++ b/target-ppc/helper.c
> @@ -1172,9 +1172,9 @@ static int mmu40x_get_physical_address (CPUState *env, 
> mmu_ctx_t *ctx,
>         case 0x1:
>         check_perms:
>             /* Check from TLB entry */
> -            /* XXX: there is a problem here or in the TLB fill code... */
> +            /* There is no longer a need to force PAGE_EXEC permission here 
> */
> +            /* because of the tlb->attr fix in helper_4xx_tlbwe_lo() */

I guess that comment is superfluous, as readers several years from now don't 
care what was broken back in the day :).

>             ctx->prot = tlb->prot;
> -            ctx->prot |= PAGE_EXEC;
>             ret = check_prot(ctx->prot, rw, access_type);
>             if (ret == -2)
>                 env->spr[SPR_40x_ESR] = 0;
> diff --git a/target-ppc/op_helper.c b/target-ppc/op_helper.c
> index 3e6db85..54356e8 100644
> --- a/target-ppc/op_helper.c
> +++ b/target-ppc/op_helper.c
> @@ -3929,7 +3929,7 @@ static inline int booke_page_size_to_tlb(target_ulong 
> page_size)
> }
> 
> /* Helpers for 4xx TLB management */
> -target_ulong helper_4xx_tlbre_lo (target_ulong entry)
> +target_ulong helper_4xx_tlbre_hi (target_ulong entry)
> {
>     ppcemb_tlb_t *tlb;
>     target_ulong ret;
> @@ -3939,7 +3939,7 @@ target_ulong helper_4xx_tlbre_lo (target_ulong entry)
>     tlb = &env->tlb[entry].tlbe;
>     ret = tlb->EPN;
>     if (tlb->prot & PAGE_VALID)
> -        ret |= 0x400;
> +        ret |= 0x40;    /* V bit is 0x40, not 0x400 */

Ouch. Mind to make it a define?

>     size = booke_page_size_to_tlb(tlb->size);
>     if (size < 0 || size > 0x7)
>         size = 1;
> @@ -3948,7 +3948,7 @@ target_ulong helper_4xx_tlbre_lo (target_ulong entry)
>     return ret;
> }
> 
> -target_ulong helper_4xx_tlbre_hi (target_ulong entry)
> +target_ulong helper_4xx_tlbre_lo (target_ulong entry)

Huh?


Alex

> {
>     ppcemb_tlb_t *tlb;
>     target_ulong ret;
>