[PATCH v4 0/6] target/arm: ISV=0 data abort emulation library

[Lucas Amaral <lucaaamaral@gmail.com>]

Add a shared emulation library for AArch64 load/store instructions that
cause ISV=0 data aborts under hardware virtualization, and wire it into
HVF (macOS) and WHPX (Windows).

When the Instruction Syndrome Valid bit is clear, the hypervisor cannot
determine the faulting instruction's target register or access size from
the syndrome alone.  This previously hit an assert(isv) and killed the
VM.  The library fetches and decodes the faulting instruction using a
decodetree-generated decoder, then emulates it directly against the vCPU
register file and memory.

The library uses its own a64-ldst.decode rather than sharing
target/arm/tcg/a64.decode — TCG's trans_* functions emit IR into a
translation block, while this library's execute directly.  Decode
patterns are kept consistent with TCG's where possible.

Changes since v3:
  - Inject synchronous external abort (matching kvm_inject_arm_sea()
    syndrome) on unhandled instruction or memory error, instead of
    silently advancing PC or returning an error.
  - Fix WHPX advance_pc bug: error paths no longer advance PC.
  - Add page-crossing guard in mem_read/mem_write to prevent partial
    side effects from cpu_memory_rw_debug().

Changes since v2:
  - Split monolithic patch into 6 incremental patches: framework, then
    one patch per coherent instruction group (Peter)
  - Removed per-backend callback ops; library uses CPUArchState directly
    with cpu_memory_rw_debug() for memory access (Mohamed)
  - Removed mock unit tests (Mohamed; kvm-unit-tests is the right
    vehicle for decoder validation)
  - Added architectural justification for separate decode file

Lucas Amaral (6):
  target/arm/emulate: add ISV=0 emulation library with load/store
    immediate
  target/arm/emulate: add load/store register offset
  target/arm/emulate: add load/store pair
  target/arm/emulate: add load/store exclusive
  target/arm/emulate: add atomic, compare-and-swap, and PAC load
  target/arm/hvf,whpx: wire ISV=0 emulation for data aborts

 target/arm/emulate/a64-ldst.decode | 293 +++++++++++
 target/arm/emulate/arm_emulate.c   | 758 +++++++++++++++++++++++++++++
 target/arm/emulate/arm_emulate.h   |  30 ++
 target/arm/emulate/meson.build     |   6 +
 target/arm/hvf/hvf.c               |  46 +-
 target/arm/meson.build             |   1 +
 target/arm/whpx/whpx-all.c         |  61 ++-
 7 files changed, 1191 insertions(+), 4 deletions(-)
 create mode 100644 target/arm/emulate/a64-ldst.decode
 create mode 100644 target/arm/emulate/arm_emulate.c
 create mode 100644 target/arm/emulate/arm_emulate.h
 create mode 100644 target/arm/emulate/meson.build

-- 
2.52.0