qemu-patch-raspberry4/target
Fredrik Noring ed4f49ba9b target/mips: Define the R5900 CPU
The primary purpose of this change is to support programs compiled by
GCC for the R5900 target and thereby run R5900 Linux distributions, for
example Gentoo.

GCC in version 7.3, by itself, by inspection of the GCC source code
and inspection of the generated machine code, for the R5900 target,
only emits two instructions that are specific to the R5900: the three-
operand MULT and MULTU. GCC and libc also emit certain MIPS III
instructions that are not part of the R5900 ISA. They are normally
trapped and emulated by the Linux kernel, and therefore need to be
treated accordingly by QEMU.

A program compiled by GCC is taken to mean source code compiled by GCC
under the restrictions above. One can, with the apparent limitations,
with a bit of effort obtain a fully functioning operating system such
as R5900 Gentoo. Strictly speaking, programs need not be compiled by
GCC to make use of this change.

Instructions and other facilities of the R5900 not implemented by this
change are intended to signal provisional exceptions. One such example
is the FPU that is not compliant with IEEE 754-1985 in system mode. It
is therefore provisionally disabled. In user space the FPU is trapped
and emulated by IEEE 754-1985 compliant software in the kernel, and
this is handled accordingly by QEMU. Another example is the 93
multimedia instructions specific to the R5900 that generate provisional
reserved instruction exception signals.

One of the benefits of running a Linux distribution under QEMU is that
programs can be compiled with a native compiler, where the host and
target are the same, as opposed to a cross-compiler, where they are
not the same. This is especially important in cases where the target
hardware does not have the resources to run a native compiler.

Problems with cross-compilation are often related to host and target
differences in integer sizes, pointer sizes, endianness, machine code,
ABI, etc. Sometimes cross-compilation is not even supported by the
build script for a given package. One effective way to avoid those
problems is to replace the cross-compiler with a native compiler. This
change of compilation methods does not resolve the inherent problems
with cross-compilation.

The native compiler naturally replaces the cross-compiler, because one
typically uses one or the other, and preferably the native compiler
when the circumstances admit this. The native compiler is also a good
test case for the R5900 QEMU user mode. Additionally, Gentoo is well-
known for compiling and installing its packages from sources.

This change has been tested with Gentoo compiled for R5900, including
native compilation of several packages under QEMU.

Reviewed-by: Aleksandar Markovic <amarkovic@wavecomp.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Fredrik Noring <noring@nocrew.org>
Signed-off-by: Aleksandar Markovic <amarkovic@wavecomp.com>
2018-10-24 15:20:31 +02:00
..
alpha target/alpha: remove tlb_flush from alpha_cpu_initfn 2018-10-18 18:58:10 -07:00
arm target/arm: Check HAVE_CMPXCHG128 at translate time 2018-10-18 19:46:53 -07:00
cris target/cris/translate: Get rid of qemu_log_separate() 2018-10-16 17:57:23 +02:00
hppa target/hppa: Raise exception 26 on emulated hardware 2018-10-16 15:32:22 -07:00
i386 Error reporting patches for 2018-10-22 2018-10-23 17:20:23 +01:00
lm32 tcg-next queue 2018-06-04 11:28:31 +01:00
m68k target/m68k: Merge disas_m68k_insn into m68k_tr_translate_insn 2018-06-11 12:43:42 +02:00
microblaze target-microblaze: Rework NOP/zero instruction handling 2018-06-15 09:05:00 +02:00
mips target/mips: Define the R5900 CPU 2018-10-24 15:20:31 +02:00
moxie tcg-next queue 2018-06-04 11:28:31 +01:00
nios2 tcg-next queue 2018-06-04 11:28:31 +01:00
openrisc target/openrisc: Fix writes to interrupt mask register 2018-07-03 22:40:33 +09:00
ppc Error reporting patches for 2018-10-22 2018-10-23 17:20:23 +01:00
riscv riscv: remove define cpu_init() 2018-09-05 09:58:38 -07:00
s390x target/s390x: Check HAVE_ATOMIC128 and HAVE_CMPXCHG128 at translate 2018-10-18 19:46:53 -07:00
sh4 sh4: fix use_icount with linux-user 2018-08-20 00:11:06 +02:00
sparc SPARC64: add icount support 2018-06-17 11:13:06 +01:00
tilegx tcg-next queue 2018-06-04 11:28:31 +01:00
tricore tcg: Pass tb and index to tcg_gen_exit_tb separately 2018-06-01 15:15:27 -07:00
unicore32 target/unicore32: remove tlb_flush from uc32_init_fn 2018-10-18 18:58:10 -07:00
xtensa target/xtensa: extract gen_check_interrupts call 2018-10-01 11:08:36 -07:00