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

Message ID 20250204152100.705610-1-mark.rutland@arm.com (mailing list archive)
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Series KVM: arm64: FPSIMD/SVE/SME fixes | expand

Message

Mark Rutland Feb. 4, 2025, 3:20 p.m. UTC 
These patches fix some isuses 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 addreses 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 addreses some mismanagement of ZCR_EL{1,2} which can result in
the host VMM unexpectedly receiving a SIGKILL. To fix this, we eagerly
swith 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 reaason about.

I've pushed these patches (with some additional debug patches that can
be used for testing) to the arm64-kvm-fpsimd-fixes-20250204 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

I've given this some basic testing on a virtual platform, booting a host
and a guest with and without constraining the guet's max SVE VL, with:

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

Any additional testing would be much appreciated.

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 | 116 +++++++++++++++++-------
 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, 170 insertions(+), 282 deletions(-)