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Control MMU for TrustZone

thiet pv
Note: This was originally posted on 20th July 2011 at http://forums.arm.com

Dear all,
I am a new bie about TrustZone. I arm learning the effect of TrustZone to MMU. I have some problems about the mechanism to manage secure/non-secure region by MMU.
Please help me to understand about them.
My dubious point described as below:
   When translation virtual address to physical address, system will use TLB table. I know that, when have a miss occur on TLB, it will find physical page from page table.
From table index of virtual address and table base address, will have first-level descriptor, the first-level descriptor will be input for page table to get physical page table from page table
then fill it to TLB table.
If page table miss, it will find physical page form external memory (RAM) and fill it to page table with it's attribute.
So when cpu stay in secure world, and access to secure physical memory
     How to know the address that cpu access include secure physical memory region or no-secure physical memory region?
     How to partition the physical memory into secure and non-secure regions?
and if know secure attribute of secure region then
     How to fill secure attribute to page table?
Please help me.
Thank you very much,
Parents
  • Arm Employee Badge
    Note: This was originally posted on 22nd July 2011 at http://forums.arm.com

    > How to specify this physical page (in the page table) is secure or non-secure?

    When the secure world makes a table walk that walk is always made as secure. When the normal world makes a table walk it is always made as non-secure.

    > How will TLB update NS and NSTID for this entry?

    NSTID = currently world of the processor.
    NS = the NS bit from the L1 descriptor if in secure-world, one otherwise.

    EDIT: corrected NS-bit description above.
Reply
  • Arm Employee Badge
    Note: This was originally posted on 22nd July 2011 at http://forums.arm.com

    > How to specify this physical page (in the page table) is secure or non-secure?

    When the secure world makes a table walk that walk is always made as secure. When the normal world makes a table walk it is always made as non-secure.

    > How will TLB update NS and NSTID for this entry?

    NSTID = currently world of the processor.
    NS = the NS bit from the L1 descriptor if in secure-world, one otherwise.

    EDIT: corrected NS-bit description above.
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