[v2,0/8] KVM: arm64: Add support for FP8

Message

Marc Zyngier Aug. 1, 2024, 9:19 a.m. UTC

Although FP8 support was merged in 6.9, the KVM side was dropped, with
no sign of it being picked up again. Given that its absence is getting
in the way of NV upstreaming (HCRX_EL2 needs fleshing out), here's a
small series addressing it.

The support is following the save/restore model established for the
rest of the FP code, with FPMR being tied to it. The sole additions
are the handling of traps in a nested context, and the corresponding
ID registers being made writable. As an extra cleanup, SVCR and FPMR
are moved into the sysreg array.

Patches are on top of v6.11-rc1. Note that this is compile-tested
only, as I have no access to FP8 HW or model (and running NV in a
model is not something I wish to entertain ever again).

* From v1 [1]

  - Correctly save/restore the guest state (duh), including pKVM
    (double duh)

  - Add a predicate for FPMR support in a VM, as this gets used more
    than twice...

[1] https://lore.kernel.org/r/[e-mail]

Marc Zyngier (8):
  KVM: arm64: Move SVCR into the sysreg array
  KVM: arm64: Add predicate for FPMR support in a VM
  KVM: arm64: Move FPMR into the sysreg array
  KVM: arm64: Add save/restore support for FPMR
  KVM: arm64: Honor trap routing for FPMR
  KVM: arm64: Expose ID_AA64FPFR0_EL1 as a writable ID reg
  KVM: arm64: Enable FP8 support when available and configured
  KVM: arm64: Expose ID_AA64PFR2_EL1 to userspace and guests

 arch/arm64/include/asm/kvm_host.h       | 20 ++++++++++--
 arch/arm64/kvm/emulate-nested.c         |  8 +++++
 arch/arm64/kvm/fpsimd.c                 |  5 +--
 arch/arm64/kvm/hyp/include/hyp/switch.h |  3 ++
 arch/arm64/kvm/hyp/nvhe/hyp-main.c      |  9 ++++++
 arch/arm64/kvm/hyp/nvhe/switch.c        |  9 ++++++
 arch/arm64/kvm/hyp/vhe/switch.c         |  3 ++
 arch/arm64/kvm/sys_regs.c               | 42 +++++++++++++++++++++++--
 8 files changed, 92 insertions(+), 7 deletions(-)