[PATCH v5] arm64: fix VTTBR_BADDR_MASK

[Joel Schopp]

>> The return is a value,not just an error code. Because of this returning
>> an error overloads that value.  0 just seemed like a convenient invalid
>> value to check since a vttbr_x of 0 is invalid, but returning a negative
>> error code would be as equally invalid.  If this is the only issue it
>> doesn't seem worth respinning the patch for, but I'll change it to
>> -EINVAL if for some reason a v6 is needed.
> Have you given up on doing the alignment check with the proper size on
> the pgd allocation for this patch?
Yes, I'd rather leave the extra check out of this patch.  If I were
changing the pgd allocation code I would make sure to add a check, or if
there were a static check there now I would update it for the dynamic
value from the hardware, but it seems unrelated to add several checks to
other parts of the code beyond those already in the patch.  I did leave
the functions in the headers such that checks like this could be added
when someone is updating the code for other reasons, say 4 level page
tables.

-Joel