[Cache] Garbage value in shared region (NS, Realm)

[bitboom]

I found that RMM reads dummy values (0xCFDFDFDF) with ACS tests.

• Read failed with ACS: Params 0x88306000
• Read succeed with TFTF: Params 0x88C01000

Originally posted by @bitboom in #145 (comment)

[jinbpark]

@bitboom ,
Not sure if this PR helps solving this,
But I added some points to wipe out a page by zero in that PR.

1. a transition from Undelegated to Delegated
2. a transition from Delegated to Undelegated

I think it's worth a try running the same ACS test with this PR. (not that high probability though)

[bitboom]

@jinbpark Thank you for the suggestion.

I found the cause of this issue.
The issue is that ACS set the shared region as Normal, Inner/Outer WB/WA/RA, but islet map the region as Device in set_pages_for_rmi.

When i changed ACS to Device temporarily, i could read the memory.

But I think our islet should change to Normal in set_pages_for_rmi. I tried it but failed :(

[jinbpark]

When i changed ACS to Device temporarily, i could read the memory.

@bitboom , This sounds like a TLB issue. (not 100% sure though)
It might be worth trying to run the below code.

pub fn set_pages_for_rmi(addr: usize, secure: bool) {
    let device_flags = helper::bits_in_reg(PTDesc::INDX, attr::mair_idx::RMM_MEM);   // try-1:  ACS (normal), RMM (normal)
    // try-2:  helper::bits_in_reg(PTDesc::INDX, attr::mair_idx::DEVICE_MEM);  --> ACS (normal), RMM (device)
    ....
    page_table.set_pages(va, phys, PAGE_SIZE, rw_flags | device_flags | secure_flags);
    ....
    unsafe {
        asm!("tlbi alle2", "dsb sy", "isb",);   // TLB flush
    }
}

[bitboom]

@jinbpark Thanks for the suggestion! I tried it but i does't work :(

The problem seems to relate with cache. When i turn off cache with cache_state_modelled=0 of acs's script, it work.
Since this is not the tfundamental solution, I detached this issue from origin PR #148.