ARM MMU Debugging - debugging

Question

I have been working on a bare metal raspberry pi project, and I am now attempting to initialize the memory management unit, following the documentation and examples.
When I run it, however, on the pi, nothing happens afterwards, and when I run it in QEMU using gdb, gdb either crashes of I get a Prefetch Abort as exception 3. Have I incorrectly set some properties such as shareability, or incorrectly used isb, or is there something I have missed?
Here is my code below
pub unsafe fn init_mmu(start: usize) {
let tcr_el1 =
(0b10 << 30) | //4kb Granule
(0b10 << 28) | //TTBR1 outer shareable
(25 << 16) | //TTBR1 size
(0b10 << 12) | //TTBR0 outer shareable
25; //TTBR0 size
let sctlr_el1 =
(1 << 4) | //Enforce EL0 stack alignment
(1 << 3) | //Enforce EL1 stack alignment
(1 << 1) | // Enforce access alignment
1; //Enable MMU
//0000_0000: nGnRnE device memory
// 0100_0100: non cacheable
let mair = 0b0000_0000_0100_0100;
let mut table = core::slice::from_raw_parts_mut(start as *mut usize, 2048);
for i in 0..(512-8) {
table[i] = (i <<9) |
(1 << 10) | // AF
(0 << 2) | //MAIR index
1; //Block entry
}
for i in (512-8)..512 {
table[i] = (i << 9) |
(1 << 10) | // AF
(1 << 2) | //MAIR index
1; //Block entry
}
table[512] = (512 << 9) |
(1 << 10) | // AF
(1 << 2) | //MAIR index
1; //Block entry
table[1024] = (0x8000000000000000) | start | 3;
table[1025] = (0x8000000000000000) | (start + 512 * 64) | 3;
write!("mair_el1", mair);
write!("ttbr0_el1", start + 1024 * 64);
asm!("isb");
write!("tcr_el1", tcr_el1);
asm!("isb");
write!("sctlr_el1", sctlr_el1);
asm!("isb");
}