Move target-* CPU file into a target/ folder

We've currently got 18 architectures in QEMU, and thus 18 target-xxx
folders in the root folder of the QEMU source tree. More architectures
(e.g. RISC-V, AVR) are likely to be included soon, too, so the main
folder of the QEMU sources slowly gets quite overcrowded with the
target-xxx folders.
To disburden the main folder a little bit, let's move the target-xxx
folders into a dedicated target/ folder, so that target-xxx/ simply
becomes target/xxx/ instead.

Acked-by: Laurent Vivier <laurent@vivier.eu> [m68k part]
Acked-by: Bastian Koppelmann <kbastian@mail.uni-paderborn.de> [tricore part]
Acked-by: Michael Walle <michael@walle.cc> [lm32 part]
Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com> [s390x part]
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com> [s390x part]
Acked-by: Eduardo Habkost <ehabkost@redhat.com> [i386 part]
Acked-by: Artyom Tarasenko <atar4qemu@gmail.com> [sparc part]
Acked-by: Richard Henderson <rth@twiddle.net> [alpha part]
Acked-by: Max Filippov <jcmvbkbc@gmail.com> [xtensa part]
Reviewed-by: David Gibson <david@gibson.dropbear.id.au> [ppc part]
Acked-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com> [cris&microblaze part]
Acked-by: Guan Xuetao <gxt@mprc.pku.edu.cn> [unicore32 part]
Signed-off-by: Thomas Huth <thuth@redhat.com>

1 files changed, 51 insertions, 0 deletions

diff --git a/target/mips/TODO b/target/mips/TODO
new file mode 100644
index 0000000000..1d782d8027
--- /dev/null
+++ b/target/mips/TODO
@@ -0,0 +1,51 @@
+Unsolved issues/bugs in the mips/mipsel backend
+-----------------------------------------------
+
+General
+-------
+- Unimplemented ASEs:
+  - MDMX
+  - SmartMIPS
+  - microMIPS DSP r1 & r2 encodings
+- MT ASE only partially implemented and not functional
+- Shadow register support only partially implemented,
+  lacks set switching on interrupt/exception.
+- 34K ITC not implemented.
+- A general lack of documentation, especially for technical internals.
+  Existing documentation is x86-centric.
+- Reverse endianness bit not implemented
+- The TLB emulation is very inefficient:
+  QEMU's softmmu implements a x86-style MMU, with separate entries
+  for read/write/execute, a TLB index which is just a modulo of the
+  virtual address, and a set of TLBs for each user/kernel/supervisor
+  MMU mode.
+  MIPS has a single entry for read/write/execute and only one MMU mode.
+  But it is fully associative with randomized entry indices, and uses
+  up to 256 ASID tags as additional matching criterion (which roughly
+  equates to 256 MMU modes). It also has a global flag which causes
+  entries to match regardless of ASID.
+  To cope with these differences, QEMU currently flushes the TLB at
+  each ASID change. Using the MMU modes to implement ASIDs hinges on
+  implementing the global bit efficiently.
+- save/restore of the CPU state is not implemented (see machine.c).
+
+MIPS64
+------
+- Userland emulation (both n32 and n64) not functional.
+
+"Generic" 4Kc system emulation
+------------------------------
+- Doesn't correspond to any real hardware. Should be removed some day,
+  U-Boot is the last remaining user.
+
+PICA 61 system emulation
+------------------------
+- No framebuffer support yet.
+
+MALTA system emulation
+----------------------
+- We fake firmware support instead of doing the real thing
+- Real firmware (YAMON) falls over when trying to init RAM, presumably
+  due to lacking system controller emulation.
+- Bonito system controller not implemented
+- MSC1 system controller not implemented