From e44e3482bdb4d0ebde2d8b41830ac2cdb07948fb Mon Sep 17 00:00:00 2001 From: Yang Zhang Date: Fri, 28 Aug 2015 09:58:54 +0800 Subject: Add qemu 2.4.0 Change-Id: Ic99cbad4b61f8b127b7dc74d04576c0bcbaaf4f5 Signed-off-by: Yang Zhang --- qemu/tcg/tci/README | 130 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 130 insertions(+) create mode 100644 qemu/tcg/tci/README (limited to 'qemu/tcg/tci/README') diff --git a/qemu/tcg/tci/README b/qemu/tcg/tci/README new file mode 100644 index 000000000..dc57f076b --- /dev/null +++ b/qemu/tcg/tci/README @@ -0,0 +1,130 @@ +TCG Interpreter (TCI) - Copyright (c) 2011 Stefan Weil. + +This file is released under the BSD license. + +1) Introduction + +TCG (Tiny Code Generator) is a code generator which translates +code fragments ("basic blocks") from target code (any of the +targets supported by QEMU) to a code representation which +can be run on a host. + +QEMU can create native code for some hosts (arm, hppa, i386, ia64, ppc, ppc64, +s390, sparc, x86_64). For others, unofficial host support was written. + +By adding a code generator for a virtual machine and using an +interpreter for the generated bytecode, it is possible to +support (almost) any host. + +This is what TCI (Tiny Code Interpreter) does. + +2) Implementation + +Like each TCG host frontend, TCI implements the code generator in +tcg-target.c, tcg-target.h. Both files are in directory tcg/tci. + +The additional file tcg/tci.c adds the interpreter. + +The bytecode consists of opcodes (same numeric values as those used by +TCG), command length and arguments of variable size and number. + +3) Usage + +For hosts without native TCG, the interpreter TCI must be enabled by + + configure --enable-tcg-interpreter + +If configure is called without --enable-tcg-interpreter, it will +suggest using this option. Setting it automatically would need +additional code in configure which must be fixed when new native TCG +implementations are added. + +System emulation should work on any 32 or 64 bit host. +User mode emulation might work. Maybe a new linker script (*.ld) +is needed. Byte order might be wrong (on big endian hosts) +and need fixes in configure. + +For hosts with native TCG, the interpreter TCI can be enabled by + + configure --enable-tcg-interpreter + +The only difference from running QEMU with TCI to running without TCI +should be speed. Especially during development of TCI, it was very +useful to compare runs with and without TCI. Create /tmp/qemu.log by + + qemu-system-i386 -d in_asm,op_opt,cpu -D /tmp/qemu.log -singlestep + +once with interpreter and once without interpreter and compare the resulting +qemu.log files. This is also useful to see the effects of additional +registers or additional opcodes (it is easy to modify the virtual machine). +It can also be used to verify native TCGs. + +Hosts with native TCG can also enable TCI by claiming to be unsupported: + + configure --cpu=unknown --enable-tcg-interpreter + +configure then no longer uses the native linker script (*.ld) for +user mode emulation. + + +4) Status + +TCI needs special implementation for 32 and 64 bit host, 32 and 64 bit target, +host and target with same or different endianness. + + | host (le) host (be) + | 32 64 32 64 +------------+------------------------------------------------------------ +target (le) | s0, u0 s1, u1 s?, u? s?, u? +32 bit | + | +target (le) | sc, uc s1, u1 s?, u? s?, u? +64 bit | + | +target (be) | sc, u0 sc, uc s?, u? s?, u? +32 bit | + | +target (be) | sc, uc sc, uc s?, u? s?, u? +64 bit | + | + +System emulation +s? = untested +sc = compiles +s0 = bios works +s1 = grub works +s2 = Linux boots + +Linux user mode emulation +u? = untested +uc = compiles +u0 = static hello works +u1 = linux-user-test works + +5) Todo list + +* TCI is not widely tested. It was written and tested on a x86_64 host + running i386 and x86_64 system emulation and Linux user mode. + A cross compiled QEMU for i386 host also works with the same basic tests. + A cross compiled QEMU for mipsel host works, too. It is terribly slow + because I run it in a mips malta emulation, so it is an interpreted + emulation in an emulation. + A cross compiled QEMU for arm host works (tested with pc bios). + A cross compiled QEMU for ppc host works at least partially: + i386-linux-user/qemu-i386 can run a simple hello-world program + (tested in a ppc emulation). + +* Some TCG opcodes are either missing in the code generator and/or + in the interpreter. These opcodes raise a runtime exception, so it is + possible to see where code must be added. + +* The pseudo code is not optimized and still ugly. For hosts with special + alignment requirements, it needs some fixes (maybe aligned bytecode + would also improve speed for hosts which support byte alignment). + +* A better disassembler for the pseudo code would be nice (a very primitive + disassembler is included in tcg-target.c). + +* It might be useful to have a runtime option which selects the native TCG + or TCI, so QEMU would have to include two TCGs. Today, selecting TCI + is a configure option, so you need two compilations of QEMU. -- cgit 1.2.3-korg