[RFC PATCH 00/11] target/arm: Introduce host_cpu_feature_supported() API

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

Hi,

Mohamed and myself are working on adding nested virtualization
support to HVF Aarch64. Mohamed approach leverages the latest
hardware features of the Apple M3+ Silicon chips [1], while mine
falls back to emulation [2] when features are not available, as
it happens with the M1 and M2 chipsets.

We want to support both methods long term, as they solve different
use cases. Therefore I'm looking for a common API for methods
added in both series.

In this series we propose the host_cpu_feature_supported() method
to check if a feature is supported by the host, allowing fall back
to TCG. KVM uses are converted, and an example -- while not really
usable without other patch applied -- is provided for HVF.

Does this look reasonable enough to pursue in that direction?

Thanks,

Phil.

[1] https://lore.kernel.org/qemu-devel/20250808070137.48716-1-mohamed@unpredictable.fr/
[2] https://lore.kernel.org/qemu-devel/20250620172751.94231-1-philmd@linaro.org/

Mohamed Mediouni (2):
  target/arm: Factor hvf_psci_get_target_el() out
  target/arm/hvf: Sync registers used at EL2

Philippe Mathieu-Daudé (9):
  accel/system: Introduce hwaccel_enabled() helper
  target/arm: Use generic hwaccel_enabled() to check 'host' cpu type
  target/arm: Restrict PMU to system mode
  target/arm: Introduce arm_hw_accel_cpu_feature_supported()
  target/arm: Introduce host_cpu_feature_supported()
  target/arm: Replace kvm_arm_pmu_supported by
    host_cpu_feature_supported
  target/arm: Replace kvm_arm_el2_supported by
    host_cpu_feature_supported
  target/arm/hvf: Consider EL2 acceleration for Silicon M3+ chipsets
  target/arm/hvf: Allow EL2/EL3 emulation on Silicon M1 / M2

 include/system/hw_accel.h | 13 +++++++
 target/arm/cpu.h          | 23 +++++++++++++
 target/arm/kvm_arm.h      | 24 -------------
 hw/arm/virt.c             |  8 +----
 target/arm/arm-qmp-cmds.c |  5 +--
 target/arm/arm_hw_accel.c | 27 +++++++++++++++
 target/arm/cpu.c          | 14 ++++----
 target/arm/cpu64.c        | 11 +++---
 target/arm/hvf/hvf.c      | 71 +++++++++++++++++++++++++++++++++++++--
 target/arm/kvm-stub.c     | 10 ------
 target/arm/kvm.c          | 33 +++++++++++++-----
 target/arm/meson.build    |  2 +-
 12 files changed, 176 insertions(+), 65 deletions(-)
 create mode 100644 target/arm/arm_hw_accel.c

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2.49.0