From 5a3c49dedf1e9e5e6a8f3e63952e2e546b6c8433 Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Fri, 7 Feb 2025 16:09:17 +0000 Subject: [PATCH] target/arm: deprecate the pxa2xx CPUs and iwMMXt emulation MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit The pxa2xx CPUs are now only useful with user-mode emulation, because we dropped all the machine types that used them in 9.2. (Technically you could alse use "-cpu pxa270" with a board model like versatilepb which doesn't sanity-check the CPU type, but that has never been a supported config.) To use them (or iwMMXt emulation) with QEMU user-mode you would need to explicitly select them with the -cpu option or the QEMU_CPU environment variable. A google search finds no examples of anybody doing this in the last decade; I don't believe the GCC folks are using QEMU to test their iwMMXt codegen either. In fact, GCC is in the process of dropping support for iwMMXT entirely. The iwMMXt emulation is thousands of lines of code in QEMU, and is now the only bit of Arm insn decode which doesn't use decodetree. We have no way to test or validate changes to it. This code is just dead weight that is almost certainly not being used by anybody. Mark it as deprecated. Signed-off-by: Peter Maydell Reviewed-by: Richard Henderson Reviewed-by: Philippe Mathieu-Daudé Message-id: 20250127112715.2936555-2-peter.maydell@linaro.org --- docs/about/deprecated.rst | 21 +++++++++++++++++++++ target/arm/cpu.c | 3 +++ target/arm/cpu.h | 1 + target/arm/tcg/cpu32.c | 36 ++++++++++++++++++++++++------------ 4 files changed, 49 insertions(+), 12 deletions(-) diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst index 4a3c302962..29de49351d 100644 --- a/docs/about/deprecated.rst +++ b/docs/about/deprecated.rst @@ -204,6 +204,27 @@ is going to be so much slower it wouldn't make sense for any serious instrumentation. Due to implementation differences there will also be anomalies in things like memory instrumentation. +linux-user mode CPUs +-------------------- + +iwMMXt emulation and the ``pxa`` CPUs (since 10.0) +'''''''''''''''''''''''''''''''''''''''''''''''''' + +The ``pxa`` CPU family (``pxa250``, ``pxa255``, ``pxa260``, +``pxa261``, ``pxa262``, ``pxa270-a0``, ``pxa270-a1``, ``pxa270``, +``pxa270-b0``, ``pxa270-b1``, ``pxa270-c0``, ``pxa270-c5``) are no +longer used in system emulation, because all the machine types which +used these CPUs were removed in the QEMU 9.2 release. These CPUs can +now only be used in linux-user mode, and to do that you would have to +explicitly select one of these CPUs with the ``-cpu`` command line +option or the ``QEMU_CPU`` environment variable. + +We don't believe that anybody is using the iwMMXt emulation, and we do +not have any tests to validate it or any real hardware or similar +known-good implementation to test against. GCC is in the process of +dropping their support for iwMMXt codegen. These CPU types are +therefore deprecated in QEMU, and will be removed in a future release. + System emulator CPUs -------------------- diff --git a/target/arm/cpu.c b/target/arm/cpu.c index 7a83b9ee34..32dc7c1e69 100644 --- a/target/arm/cpu.c +++ b/target/arm/cpu.c @@ -2758,6 +2758,9 @@ static void cpu_register_class_init(ObjectClass *oc, void *data) acc->info = data; cc->gdb_core_xml_file = "arm-core.xml"; + if (acc->info->deprecation_note) { + cc->deprecation_note = acc->info->deprecation_note; + } } void arm_cpu_register(const ARMCPUInfo *info) diff --git a/target/arm/cpu.h b/target/arm/cpu.h index 2213c27734..c2d2d99b46 100644 --- a/target/arm/cpu.h +++ b/target/arm/cpu.h @@ -1118,6 +1118,7 @@ struct ArchCPU { typedef struct ARMCPUInfo { const char *name; + const char *deprecation_note; void (*initfn)(Object *obj); void (*class_init)(ObjectClass *oc, void *data); } ARMCPUInfo; diff --git a/target/arm/tcg/cpu32.c b/target/arm/tcg/cpu32.c index 2ad2182525..0f1c5bc87e 100644 --- a/target/arm/tcg/cpu32.c +++ b/target/arm/tcg/cpu32.c @@ -1026,19 +1026,31 @@ static const ARMCPUInfo arm_tcg_cpus[] = { { .name = "ti925t", .initfn = ti925t_initfn }, { .name = "sa1100", .initfn = sa1100_initfn }, { .name = "sa1110", .initfn = sa1110_initfn }, - { .name = "pxa250", .initfn = pxa250_initfn }, - { .name = "pxa255", .initfn = pxa255_initfn }, - { .name = "pxa260", .initfn = pxa260_initfn }, - { .name = "pxa261", .initfn = pxa261_initfn }, - { .name = "pxa262", .initfn = pxa262_initfn }, + { .name = "pxa250", .initfn = pxa250_initfn, + .deprecation_note = "iwMMXt CPUs are no longer supported", }, + { .name = "pxa255", .initfn = pxa255_initfn, + .deprecation_note = "iwMMXt CPUs are no longer supported", }, + { .name = "pxa260", .initfn = pxa260_initfn, + .deprecation_note = "iwMMXt CPUs are no longer supported", }, + { .name = "pxa261", .initfn = pxa261_initfn, + .deprecation_note = "iwMMXt CPUs are no longer supported", }, + { .name = "pxa262", .initfn = pxa262_initfn, + .deprecation_note = "iwMMXt CPUs are no longer supported", }, /* "pxa270" is an alias for "pxa270-a0" */ - { .name = "pxa270", .initfn = pxa270a0_initfn }, - { .name = "pxa270-a0", .initfn = pxa270a0_initfn }, - { .name = "pxa270-a1", .initfn = pxa270a1_initfn }, - { .name = "pxa270-b0", .initfn = pxa270b0_initfn }, - { .name = "pxa270-b1", .initfn = pxa270b1_initfn }, - { .name = "pxa270-c0", .initfn = pxa270c0_initfn }, - { .name = "pxa270-c5", .initfn = pxa270c5_initfn }, + { .name = "pxa270", .initfn = pxa270a0_initfn, + .deprecation_note = "iwMMXt CPUs are no longer supported", }, + { .name = "pxa270-a0", .initfn = pxa270a0_initfn, + .deprecation_note = "iwMMXt CPUs are no longer supported", }, + { .name = "pxa270-a1", .initfn = pxa270a1_initfn, + .deprecation_note = "iwMMXt CPUs are no longer supported", }, + { .name = "pxa270-b0", .initfn = pxa270b0_initfn, + .deprecation_note = "iwMMXt CPUs are no longer supported", }, + { .name = "pxa270-b1", .initfn = pxa270b1_initfn, + .deprecation_note = "iwMMXt CPUs are no longer supported", }, + { .name = "pxa270-c0", .initfn = pxa270c0_initfn, + .deprecation_note = "iwMMXt CPUs are no longer supported", }, + { .name = "pxa270-c5", .initfn = pxa270c5_initfn, + .deprecation_note = "iwMMXt CPUs are no longer supported", }, #ifndef TARGET_AARCH64 { .name = "max", .initfn = arm_max_initfn }, #endif -- 2.30.2