[PATCH v3 00/11] KVM: arm64: Fix handling of host fpsimd/sve state in protected mode

[Fuad Tabba <tabba@google.com>]

Changes since v2 [1]
- Rebased on Linux 6.10-rc1 (1613e604df0c)
- Apply suggestions/fixes suggested for V2 (Marc)
- Add an isb() to __hyp_sve_restore_guest()
- Squash patch that introduces kvm_host_sve_max_vl with following
  patch, since it's used there
- Some refactoring and tidying up
- Introduce and use sve_cond_update_zcr_vq_isb(), which only does
  an isb() if ZCR is updated (RFC, next to last patch)
- Remove sve_cond_update_zcr_vq_*, since it's not likely to help
  much (RFC, last patch)

With the KVM host data rework [2], handling of fpsimd and sve
state in protected mode is done at hyp. For protected VMs, we
don't want to leak any guest state to the host, including whether
a guest has used fpsimd/sve.

To complete the work started with the host data rework, in
regards to protected mode, ensure that the host's fpsimd context
and its sve context are restored on guest exit, since the rework
has hidden the fpsimd/sve state from the host.

This patch series eagerly restores the host fpsimd/sve state on
guest exit when running in protected mode, which happens only if
the guest has used fpsimd/sve. This means that the saving of the
state is lazy, similar to the behavior of KVM in other modes, but
the restoration of the host state is eager.

The last two patches are not essential to this patch series, and
the last one undoes the next-to-last. Please consider only one
(or neither) of these two patches for inclusion.

This series is based on Linux 6.10-rc1 (1613e604df0c).

Tested on qemu, with the kernel sve stress tests.

Cheers,
/fuad

[1] https://lore.kernel.org/all/20240521163720.3812851-1-tabba@google.com/
[2] https://lore.kernel.org/all/20240322170945.3292593-1-maz@kernel.org/

Fuad Tabba (11):
  KVM: arm64: Reintroduce __sve_save_state
  KVM: arm64: Abstract set/clear of CPTR_EL2 bits behind helper
  KVM: arm64: Specialize handling of host fpsimd state on trap
  KVM: arm64: Allocate memory mapped at hyp for host sve state in pKVM
  KVM: arm64: Eagerly restore host fpsimd/sve state in pKVM
  KVM: arm64: Consolidate initializing the host data's fpsimd_state/sve
    in pKVM
  KVM: arm64: Refactor CPACR trap bit setting/clearing to use ELx format
  KVM: arm64: Add an isb before restoring guest sve state
  KVM: arm64: Do not use sve_cond_update_zcr updating with
    ZCR_ELx_LEN_MASK
  KVM: arm64: Do not perform an isb() if ZCR_EL2 isn't updated
  KVM: arm64: Drop sve_cond_update_zcr_vq_*

 arch/arm64/include/asm/el2_setup.h      |  6 +-
 arch/arm64/include/asm/fpsimd.h         | 11 ----
 arch/arm64/include/asm/kvm_arm.h        |  6 ++
 arch/arm64/include/asm/kvm_emulate.h    | 71 +++++++++++++++++++++--
 arch/arm64/include/asm/kvm_host.h       | 25 +++++++-
 arch/arm64/include/asm/kvm_hyp.h        |  2 +
 arch/arm64/include/asm/kvm_pkvm.h       |  9 +++
 arch/arm64/kvm/arm.c                    | 76 +++++++++++++++++++++++++
 arch/arm64/kvm/fpsimd.c                 |  8 +--
 arch/arm64/kvm/hyp/fpsimd.S             |  6 ++
 arch/arm64/kvm/hyp/include/hyp/switch.h | 36 ++++++------
 arch/arm64/kvm/hyp/include/nvhe/pkvm.h  |  1 -
 arch/arm64/kvm/hyp/nvhe/hyp-main.c      | 75 +++++++++++++++++++++---
 arch/arm64/kvm/hyp/nvhe/pkvm.c          | 17 ++----
 arch/arm64/kvm/hyp/nvhe/setup.c         | 25 +++++++-
 arch/arm64/kvm/hyp/nvhe/switch.c        | 24 +++++++-
 arch/arm64/kvm/hyp/vhe/switch.c         | 12 ++--
 arch/arm64/kvm/reset.c                  |  3 +
 18 files changed, 342 insertions(+), 71 deletions(-)


base-commit: 1613e604df0cd359cf2a7fbd9be7a0bcfacfabd0
-- 
2.45.1.288.g0e0cd299f1-goog