[PATCH v2 0/8] KVM: arm64: FPSIMD/SVE/SME fixes

[Mark Rutland]

These patches fix some issues with the way KVM manages FPSIMD/SVE/SME
state. The series supersedes my earlier attempt at fixing the host SVE
state corruption issue:

  https://lore.kernel.org/linux-arm-kernel/20250121100026.3974971-1-mark.rutland@arm.com/

Patch 1 addresses the host SVE state corruption issue by always saving
and unbinding the host state when loading a vCPU, as discussed on the
earlier patch:

  https://lore.kernel.org/linux-arm-kernel/Z4--YuG5SWrP_pW7@J2N7QTR9R3/
  https://lore.kernel.org/linux-arm-kernel/86plkful48.wl-maz@kernel.org/

Patches 2 to 4 remove code made redundant by patch 1. These probably
warrant backporting along with patch 1 as there is some historical
brokenness in the code they remove.

Patches 5 to 7 are preparatory refactoring for patch 8, and are not
intended to have any functional impact.

Patch 8 addresses some mismanagement of ZCR_EL{1,2} which can result in
the host VMM unexpectedly receiving a SIGKILL. To fix this, we eagerly
switch ZCR_EL{1,2} at guest<->host transitions, as discussed on another
series:

  https://lore.kernel.org/linux-arm-kernel/Z4pAMaEYvdLpmbg2@J2N7QTR9R3/
  https://lore.kernel.org/linux-arm-kernel/86o6zzukwr.wl-maz@kernel.org/
  https://lore.kernel.org/linux-arm-kernel/Z5Dc-WMu2azhTuMn@J2N7QTR9R3/

The end result is that KVM loses ~100 lines of code, and becomes a bit
simpler to reason about.

I've pushed these patches to the  arm64-kvm-fpsimd-fixes-20250206 tag on
my kernel.org repo:

  https://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git/
  git://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git

The (unstable) arm64/kvm/fpsimd-fixes branch in that repo contains the
fixes plus additional debug patches I've used for testing. I've given
this some basic testing on a virtual platform, booting a host and a
guest with and without constraining the guest's max SVE VL, with:

* kvm_arm.mode=vhe
* kvm_arm.mode=nvhe
* kvm_arm.mode=protected (IIUC this will default to hVHE)

Since v1 [1]:
* Address some additional compiler warnings in patch 7
* Use ZCR_EL1 alias in VHE code
* Fold in Tested-by and Reviewed-by tags
* Fix typos

[1] https://lore.kernel.org/linux-arm-kernel/20250204152100.705610-1-mark.rutland@arm.com/

Mark.

Mark Rutland (8):
  KVM: arm64: Unconditionally save+flush host FPSIMD/SVE/SME state
  KVM: arm64: Remove host FPSIMD saving for non-protected KVM
  KVM: arm64: Remove VHE host restore of CPACR_EL1.ZEN
  KVM: arm64: Remove VHE host restore of CPACR_EL1.SMEN
  KVM: arm64: Refactor CPTR trap deactivation
  KVM: arm64: Refactor exit handlers
  KVM: arm64: Mark some header functions as inline
  KVM: arm64: Eagerly switch ZCR_EL{1,2}

 arch/arm64/include/asm/kvm_emulate.h    |  42 --------
 arch/arm64/include/asm/kvm_host.h       |  22 +----
 arch/arm64/kernel/fpsimd.c              |  25 -----
 arch/arm64/kvm/arm.c                    |   8 --
 arch/arm64/kvm/fpsimd.c                 | 100 ++-----------------
 arch/arm64/kvm/hyp/include/hyp/switch.h | 125 +++++++++++++++++-------
 arch/arm64/kvm/hyp/nvhe/hyp-main.c      |  15 ++-
 arch/arm64/kvm/hyp/nvhe/switch.c        |  91 ++++++++---------
 arch/arm64/kvm/hyp/vhe/switch.c         |  33 ++++---
 9 files changed, 174 insertions(+), 287 deletions(-)

-- 
2.30.2