Currently Arch::virt_is_valid is empty stub that returns true for every virtual address for aarch64. armv8 has a notion of valid virtual addresses, which is controlled by TCR_EL1::T1SZ and TCR_EL1::T0SZ for kernel space and user space respectively.
Use TCR_EL1::T1SZ register to determine if virtual address is valid or not
PS: seems like T1SZ is actually hard-coded and always has value of 48. Should we rely on that or better to create a function which will always work?
Signed-off-by: Pavel Skripkin firstname.lastname@example.org