[PATCH v4 0/5] KVM: arm64: Writable MIDR/REVIDR (and associated baggage)

[Oliver Upton <oliver.upton@linux.dev>]

This is hopefully the last take on the writable MIDR/REVIDR/AIDR series.

I've restructured things in order to work around the existing
shortcomings, have a stable-worthy backport for SMIDR_EL1, and avoid
breaking ABI.

I personally hate using a capability for this, but given the subtlety of
the issue (and our habit of breaking save/restore) it is probably best
to put userspace in the driver's seat.

v3: https://lore.kernel.org/kvmarm/20250218163443.32836-1-sebott@redhat.com/

v3 -> v4:
 - Trap SMIDR_EL1 accesses so they actually UNDEF
 - Snapshot MIDR, REVIDR, and AIDR from the boot CPU
 - Require buy-in from userspace to make ID registers writable

Oliver Upton (2):
  KVM: arm64: Set HCR_EL2.TID1 unconditionally
  KVM: arm64: Load VPIDR_EL2 with the VM's MIDR_EL1 value

Sebastian Ott (3):
  KVM: arm64: Maintain per-VM copy of implementation ID regs
  KVM: arm64: Allow userspace to change the implementation ID registers
  KVM: selftests: arm64: Test writes to MIDR,REVIDR,AIDR

 Documentation/virt/kvm/api.rst                |  18 ++
 arch/arm64/include/asm/kvm_arm.h              |   4 +-
 arch/arm64/include/asm/kvm_host.h             |  11 +
 arch/arm64/kvm/arm.c                          |   9 +
 arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h    |  14 +-
 arch/arm64/kvm/hyp/nvhe/sysreg-sr.c           |   4 +-
 arch/arm64/kvm/hyp/vhe/sysreg-sr.c            |  28 +--
 arch/arm64/kvm/sys_regs.c                     | 219 +++++++++++-------
 include/uapi/linux/kvm.h                      |   1 +
 .../testing/selftests/kvm/arm64/set_id_regs.c |  37 ++-
 10 files changed, 229 insertions(+), 116 deletions(-)


base-commit: 2014c95afecee3e76ca4a56956a936e23283f05b
-- 
2.39.5