TWO-LEVEL LMTT STRUCTURE(9)

✨ Two-Level LMTT Structure(9) ✨

okay bestie, welcome to Two-Level LMTT Structure(9) from the Kernel API Manual — and it's giving address-translation lore. no cap, we are keeping every single detail, so let's get into it.

Here's the numeric tea, fresh and iconic:

• LMHAW — that's Local Memory Host Address Width, and it is 37 bit (128GB). slay.
• LMGAW — that's Local Memory Guest Address Width, and it is also 37 bit (128GB). periodt.

The following figure illustrates the structure and function of the 2L LMTT — honestly, it's the main character of this page, so give it your full attention:

                  LMTT Directory
                 (1 Entry per VF)
                  +-----------+                     LMTT (per VF)
                  |           |                     +-----------+
                  |           |                     |           |
                  |           |          index:     |           |
                  |           |          LMEM VF    +===========+
                  |           |          offset --> |    PTE    | ==> LMEM PF offset
                  |           |                     +===========+
         index:   +===========+                     |           |
         VFID --> |    PDE    |  -----------------> +-----------+
                  +===========+                    /              .
                  |           |                   /                 .
                  |           |                  /                    .
                  |           |                 /                       .
                  +-----------+ <== [LMTT Directory Ptr]                  .
                 /                           /                             .
                /                        +-----------+-----------------+------+---+
               /                         | 31:HAW-16 |        HAW-17:5 |  4:1 | 0 |
              /                          +===========+=================+======+===+
             /                           |  Reserved | LMEM Page (2MB) | Rsvd | V |
            /                            +-----------+-----------------+------+---+
           /                         .
         +-----------+-----------------+------+---+
         | 31:HAW-12 |        HAW-13:4 |  3:1 | 0 |
         +===========+=================+======+===+
         |  Reserved | LMTT Ptr (64KB) | Rsvd | V |
         +-----------+-----------------+------+---+

👀 SEE ALSO 👀

• Kernel file ./drivers/gpu/drm/xe/xe_lmtt_2l.c — go peek, iykyk. 🦋

Signed off with main-character energy: source/version is ./drivers/gpu/drm/xe, the date is October 2026, and this page is Two-Level LMTT Structure(9). bye bestie! 💖🎀✨