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Annotation of qemu/target-mips/TODO, revision 1.1.1.5

1.1       root        1: Unsolved issues/bugs in the mips/mipsel backend
                      2: -----------------------------------------------
                      3: 
                      4: General
                      5: -------
1.1.1.2   root        6: - Unimplemented ASEs:
                      7:   - MDMX
                      8:   - SmartMIPS
                      9:   - DSP r1
                     10:   - DSP r2
                     11: - MT ASE only partially implemented and not functional
                     12: - Shadow register support only partially implemented,
                     13:   lacks set switching on interrupt/exception.
                     14: - 34K ITC not implemented.
                     15: - A general lack of documentation, especially for technical internals.
                     16:   Existing documentation is x86-centric.
                     17: - Reverse endianness bit not implemented
                     18: - The TLB emulation is very inefficient:
1.1.1.5 ! root       19:   QEMU's softmmu implements a x86-style MMU, with separate entries
1.1.1.2   root       20:   for read/write/execute, a TLB index which is just a modulo of the
                     21:   virtual address, and a set of TLBs for each user/kernel/supervisor
                     22:   MMU mode.
                     23:   MIPS has a single entry for read/write/execute and only one MMU mode.
                     24:   But it is fully associative with randomized entry indices, and uses
                     25:   up to 256 ASID tags as additional matching criterion (which roughly
                     26:   equates to 256 MMU modes). It also has a global flag which causes
                     27:   entries to match regardless of ASID.
1.1.1.5 ! root       28:   To cope with these differences, QEMU currently flushes the TLB at
1.1.1.2   root       29:   each ASID change. Using the MMU modes to implement ASIDs hinges on
                     30:   implementing the global bit efficiently.
1.1.1.3   root       31: - save/restore of the CPU state is not implemented (see machine.c).
1.1       root       32: 
                     33: MIPS64
                     34: ------
1.1.1.2   root       35: - Userland emulation (both n32 and n64) not functional.
1.1       root       36: 
                     37: "Generic" 4Kc system emulation
                     38: ------------------------------
1.1.1.3   root       39: - Doesn't correspond to any real hardware. Should be removed some day,
                     40:   U-Boot is the last remaining user.
1.1       root       41: 
1.1.1.2   root       42: PICA 61 system emulation
                     43: ------------------------
                     44: - No framebuffer support yet.
                     45: 
1.1       root       46: MALTA system emulation
                     47: ----------------------
                     48: - We fake firmware support instead of doing the real thing
1.1.1.3   root       49: - Real firmware (YAMON) falls over when trying to init RAM, presumably
                     50:   due to lacking system controller emulation.
1.1.1.2   root       51: - Bonito system controller not implemented
                     52: - MSC1 system controller not implemented

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