[PATCH v4 00/10] arm64: Add support for FEAT_E2H0, or lack thereof

[Marc Zyngier]

Since ARMv8.1, the architecture has grown the VHE feature, which makes
EL2 a superset of EL1. With ARMv9.5 (and retroactively allowed from
ARMv8.1), the architecture allows implementations to have VHE as the
*only* implemented behaviour, meaning that HCR_EL2.E2H can be
implemented as RES1. As a follow-up, HCR_EL2.NV1 can also be
implemented as RES0, making the VHE-ness of the architecture
recursive.

This has a number of consequences, both at boot time and for KVM,
though the changes at that level are pretty minor.

The real meat of this series is on the cpufeature front, as FEAT_E2H0
is a *negative* feature, where 0b1111 (-1) represents E2H being RES1
and 0b1110 (-2) additionally indicates that NV1 is RES0. Fun, isn't
it?

As a bonus, a popular crop of non-compliant HW gets promoted as the
first batch of non-zero E2H0 users, making things easy for KVM.

This series is a prefix for the NV support.

* From v3 [3]:
  - Dropped the capability for E2H being RES1
  - Dropped the MIDR-based IDreg override
  - Rebased on 6.8-rc1

* From v2 [2]:
  - Moved some SYS_FIELD_VALUE() usage to the correct patch
  - Fixed a couple of spelling mistakes
  - Picked RBs from Suzuki (thanks!)

* From v1 [1]:
  - Added a SYS_FIELD_VALUE() helper to handle the concatenation
    of various fields
  - Only test for the top bit of ID_AA64MMFR4_EL1.E2H0 to decide
    whether HCR_EL2.E2H is RES1.
  - Picked RBs from Oliver (thanks!)
  - Rebased on 6.7-rc2

[1] https://lore.kernel.org/r/20231113174244.3026520-1-maz@kernel.org
[2] https://lore.kernel.org/r/20231120123721.851738-1-maz@kernel.org
[3] https://lore.kernel.org/r/20231127114559.990314-1-maz@kernel.org

Marc Zyngier (10):
  arm64: Add macro to compose a sysreg field value
  arm64: cpufeatures: Correctly handle signed values
  arm64: cpufeature: Correctly display signed override values
  arm64: sysreg: Add layout for ID_AA64MMFR4_EL1
  arm64: cpufeature: Add ID_AA64MMFR4_EL1 handling
  arm64: cpufeature: Detect HCR_EL2.NV1 being RES0
  arm64: Treat HCR_EL2.E2H as RES1 when ID_AA64MMFR4_EL1.E2H0 is
    negative
  KVM: arm64: Expose ID_AA64MMFR4_EL1 to guests
  KVM: arm64: Force guest's HCR_EL2.E2H RES1 when NV1 is not implemented
  KVM: arm64: Handle Apple M2 as not having HCR_EL2.NV1 implemented

 arch/arm64/include/asm/cpu.h         |   1 +
 arch/arm64/include/asm/cpufeature.h  |   1 +
 arch/arm64/include/asm/kvm_emulate.h |   3 +-
 arch/arm64/include/asm/sysreg.h      |   5 +-
 arch/arm64/kernel/cpufeature.c       | 103 ++++++++++++++++++++++++---
 arch/arm64/kernel/cpuinfo.c          |   1 +
 arch/arm64/kernel/head.S             |  23 +++---
 arch/arm64/kvm/nested.c              |   7 ++
 arch/arm64/kvm/sys_regs.c            |  17 ++++-
 arch/arm64/tools/cpucaps             |   1 +
 arch/arm64/tools/sysreg              |  37 ++++++++++
 11 files changed, 176 insertions(+), 23 deletions(-)

-- 
2.39.2