[PATCH v4 0/5] initialize SCTRL2_ELx

[Yeoreum Yun]

This series introduces initial support for the SCTLR2_ELx registers in Linux.
The feature is optional starting from ARMv8.8/ARMv9.3,
and becomes mandatory from ARMv8.9/ARMv9.4.

Currently, Linux has no strict need to modify SCTLR2_ELx--
at least assuming that firmware initializes
these registers to reasonable defaults.

However, several upcoming architectural features will require configuring
control bits in these registers.
Notable examples include FEAT_PAuth_LR and FEAT_CPA2.

Patch History
==============
from v3 to v4:
  - integrate set_sctlr2_elx() and __set_sctlr2_elx() to set_sctlr2_elx()
    without isb()
  - fix the wrong register setting in set_sctlr2_elx().
  - add initialise SCTLR2_EL2 at HVC_SOFT_RESTART.
  - https://lore.kernel.org/all/20250813120118.3953541-1-yeoreum.yun@arm.com/

from v2 to v3:
  - rewrite commit messages.
  - fix missing SCTLR2_EL2 synchonization at boot.
  - merging the __kvm_host_psci_cpu_entry() changes into patch #1
  - https://lore.kernel.org/all/20250811163340.1561893-1-yeoreum.yun@arm.com/

from v1 to v2:
  - rebase to v6.17-rc1
  - https://lore.kernel.org/all/20250804121724.3681531-1-yeoreum.yun@arm.com/

Yeoreum Yun (5):
  arm64: make SCTLR2_EL1 accessible
  arm64: initialise SCTLR2_ELx register at boot time
  arm64: save/restore SCTLR2_EL1 when cpu_suspend()/resume()
  arm64: initialise SCTLR2_EL1 at cpu_soft_restart()
  arm64: make the per-task SCTLR2_EL1

 arch/arm64/include/asm/assembler.h   | 15 +++++++++++++++
 arch/arm64/include/asm/el2_setup.h   | 17 +++++++++++++++--
 arch/arm64/include/asm/processor.h   |  3 +++
 arch/arm64/include/asm/suspend.h     |  2 +-
 arch/arm64/include/asm/sysreg.h      |  5 +++++
 arch/arm64/kernel/cpu-reset.S        |  4 ++++
 arch/arm64/kernel/head.S             |  5 +++++
 arch/arm64/kernel/hyp-stub.S         | 10 ++++++++++
 arch/arm64/kernel/process.c          |  9 +++++++++
 arch/arm64/kvm/hyp/nvhe/hyp-init.S   |  3 +++
 arch/arm64/kvm/hyp/nvhe/psci-relay.c |  3 +++
 arch/arm64/mm/proc.S                 | 24 ++++++++++++++++--------
 12 files changed, 89 insertions(+), 11 deletions(-)


base-commit: 8f5ae30d69d7543eee0d70083daf4de8fe15d585
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LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}