[for-10.1,0/9] target/arm: Remove TYPE_AARCH64_CPU class

Message

Peter Maydell March 17, 2025, 2:28 p.m. UTC

Currently we have a class hierarchy for Arm CPUs where
all the 32-bit CPUs (including M-profile) inherit directly
from TYPE_ARM_CPU, but the 64-bit CPUs inherit from
TYPE_AARCH64_CPU, which is a subclass of TYPE_ARM_CPU.
This subclass does essentially two things:
 * it sets up fields and methods for the gdbstub so that
   the gdbstub presents an AArch64 CPU to gdb rather than
   an AArch32 one
 * it defines the 'aarch64' CPU property which you can use
   with KVM to disable AArch64 and create a 32-bit VM
   (with "-cpu host,aarch64=off")

This is a bit weird, because the 32-bit CPU you create with
KVM and aarch64=off is still a subclass of TYPE_AARCH64_CPU.
It also still presents gdb with an AArch64 CPU, so you
effectively can't use the gdbstub with this kind of VM.

This patchseries removes TYPE_AARCH64_CPU so that all CPUs,
both AArch32 and AArch64, directly inherit from TYPE_ARM_CPU.
This lets us fix the bug with gdbstub and "aarch64=off".

Most of the gdbstub related CPUClass fields are already methods,
so we can make the existing TYPE_ARM_CPU ones redirect to
the AArch64 functions if ARM_FEATURE_AARCH64 is set. The
odd-one-out is gdb_core_xml_file, so we have to add a new
optional method gdb_get_core_xml_file to allow us to select
the right XML file at runtime. (We could, like gdb_arch_name,
simply replace the existing static string field with the
method for all targets, but at least for this patchset I
didn't want to get into that complexity.)

We make the 'aarch64' property be an object property defined
if the ARM_FEATURE_AARCH64 is set rather than a class property;
this brings it into line with our other CPU properties.

Once we've done that and removed a check on TYPE_AARCH64_CPU
in the KVM code that hasn't been needed since we removed
32-bit Arm host KVM support, we can remove TYPE_AARCH64_CPU
entirely.

(The rationale here is that I think we should be able to
enable 'aarch64=off' for TCG CPUs too, so this will become
less of an odd KVM-specific corner case, and this seemed
worth cleaning up.)

thanks
-- PMM

Peter Maydell (9):
  core/cpu.h: gdb_arch_name string should not be freed
  gdbstub: Allow gdb_core_xml_file to be set at runtime
  target/arm: Handle AArch64 in TYPE_ARM_CPU gdb_arch_name
  target/arm: Handle gdb_core_xml_file in TYPE_ARM_CPU
  target/arm: Handle AArch64 gdb read/write regs in TYPE_ARM_CPU
  target/arm: Present AArch64 gdbstub based on ARM_FEATURE_AARCH64
  target/arm: Move aarch64 CPU property code to TYPE_ARM_CPU
  target/arm/kvm: don't check TYPE_AARCH64_CPU
  target/arm: Remove TYPE_AARCH64_CPU

 include/hw/core/cpu.h    |  8 +++-
 target/arm/cpu-qom.h     |  5 ---
 target/arm/cpu.h         |  4 --
 target/arm/internals.h   |  7 ++-
 gdbstub/gdbstub.c        | 23 ++++++++--
 target/arm/cpu.c         | 55 ++++++++++++++++++++++-
 target/arm/cpu64.c       | 94 +---------------------------------------
 target/arm/gdbstub.c     | 12 +++++
 target/arm/kvm.c         |  3 +-
 target/arm/tcg/cpu-v7m.c |  1 -
 target/arm/tcg/cpu64.c   |  2 +-
 11 files changed, 101 insertions(+), 113 deletions(-)