1 Unsolved issues/bugs in the mips/mipsel backend 2 ----------------------------------------------- 3 4 General 5 ------- 6 - Unimplemented ASEs: 7 - MIPS16 8 - MDMX 9 - SmartMIPS 10 - DSP r1 11 - DSP r2 12 - MT ASE only partially implemented and not functional 13 - Shadow register support only partially implemented, 14 lacks set switching on interrupt/exception. 15 - 34K ITC not implemented. 16 - A general lack of documentation, especially for technical internals. 17 Existing documentation is x86-centric. 18 - Reverse endianness bit not implemented 19 - The TLB emulation is very inefficient: 20 Qemu's softmmu implements a x86-style MMU, with separate entries 21 for read/write/execute, a TLB index which is just a modulo of the 22 virtual address, and a set of TLBs for each user/kernel/supervisor 23 MMU mode. 24 MIPS has a single entry for read/write/execute and only one MMU mode. 25 But it is fully associative with randomized entry indices, and uses 26 up to 256 ASID tags as additional matching criterion (which roughly 27 equates to 256 MMU modes). It also has a global flag which causes 28 entries to match regardless of ASID. 29 To cope with these differences, Qemu currently flushes the TLB at 30 each ASID change. Using the MMU modes to implement ASIDs hinges on 31 implementing the global bit efficiently. 32 - save/restore of the CPU state is not implemented (see machine.c). 33 34 MIPS64 35 ------ 36 - Userland emulation (both n32 and n64) not functional. 37 38 "Generic" 4Kc system emulation 39 ------------------------------ 40 - Doesn't correspond to any real hardware. Should be removed some day, 41 U-Boot is the last remaining user. 42 43 PICA 61 system emulation 44 ------------------------ 45 - No framebuffer support yet. 46 47 MALTA system emulation 48 ---------------------- 49 - We fake firmware support instead of doing the real thing 50 - Real firmware (YAMON) falls over when trying to init RAM, presumably 51 due to lacking system controller emulation. 52 - Bonito system controller not implemented 53 - MSC1 system controller not implemented 54
