Re: [Qemu-devel] [PATCH v3 31/31] target-arm: Add v8 mmu translation support

[Peter Maydell]

On 26 February 2014 19:47, Rob Herring <address@hidden> wrote:
> Tagged addresses would probably be broken in other places as well as I
> don't think we handle all of the BranchTo() pseudocode. I'm not sure
> anything is using tagged addresses ATM.

Yeah, I agree we would need to fix other places too at some point.

> I've fixed the above issues and found another issue on v7 LPAE with
> the ttbr masking. I believe it to be correct now, but my formula does
> not match the pseudocode which is:
>
> baselowerbound = 3 + tablesize - stride*(3-level) - grainsize;
> baseaddress = base<47:baselowerbound>:Zeros(baselowerbound);
>
> This formula appears to be wrong AFAICT. Take a couple of examples:
>
> level=1,tablesize=32: 3 + 32 - 12*2 - 9 = 2 (correct value is 5)
> level=0,tablesize=48: 3 + 48 - 12*3 - 9 = 6 (correct value is 12)

Your examples seem to have the stride and grainsize the wrong
way round. grainsize is 16, 14, or 12, and stride is grainsize - 3.
So for the first one: 3 + 32 - 9*2 - 12 == 5
and for the second: 3 + 48 - 9*3 - 12 == 12

thanks
-- PMM