Add support for FEAT_{LS64, LS64_V} and related tests

Armv8.7 introduces single-copy atomic 64-byte loads and stores
instructions and its variants named under FEAT_{LS64, LS64_V}.
Add support for Armv8.7 FEAT_{LS64, LS64_V}:
- Add identifying and enabling in the cpufeature list
- Expose the support of these features to userspace through HWCAP3 and cpuinfo
- Add related hwcap test
- Handle the trap of unsupported memory (normal/uncacheable) access in a VM

A real scenario for this feature is that the userspace driver can make use of
this to implement direct WQE (workqueue entry) - a mechanism to fill WQE
directly into the hardware.

Picked Marc's 2 patches form [1] for handling the LS64 trap in a VM on emulated
MMIO and the introduce of KVM_EXIT_ARM_LDST64B.

As Yicong has left HiSilicon, I will help to continue to upstream this patchset.

[1] https://lore.kernel.org/linux-arm-kernel/20240815125959.2...

Tested with updated hwcap test(host in VHE):
[root@localhost tmp]# ./hwcap
[...]
# LS64 present
ok 226 cpuinfo_match_LS64
ok 227 sigill_LS64
ok 228 # SKIP sigbus_LS64
# LS64_V present
ok 229 cpuinfo_match_LS64_V
ok 230 sigill_LS64_V
ok 231 # SKIP sigbus_LS64_V
# 121 skipped test(s) detected. Consider enabling relevant config options to improve coverage.
# Totals: pass:110 fail:0 xfail:0 xpass:0 skip:121 error:0

Tested with updated hwcap test(guest in VHE):
root@localhost:/mnt# ./hwcap
[...]
# LS64 present
ok 226 cpuinfo_match_LS64
ok 227 sigill_LS64
ok 228 # SKIP sigbus_LS64
# LS64_V present
ok 229 cpuinfo_match_LS64_V
ok 230 sigill_LS64_V
ok 231 # SKIP sigbus_LS64_V
# 121 skipped test(s) detected. Consider enabling relevant config options to improve coverage.
# Totals: pass:110 fail:0 xfail:0 xpass:0 skip:121 error:0

Tested nVHE case as well, same log as above.

Change since v5:
- Rebase on v6.18-rc2 and fix the conflicts
- Add more description in elf_hwcaps.rst as suggested by Catalin Marinas
Link: https://lore.kernel.org/all/20250818064806.25417-1-yangyi...

Change since v4:
- Rebase on v6.17-rc2 and fix the conflicts
Link: https://lore.kernel.org/linux-arm-kernel/20250715081356.1...

Change since v3:
- Inject DABT fault for LS64 fault on unsupported memory but with valid memslot
Link: https://lore.kernel.org/linux-arm-kernel/20250626080906.6...

Change since v2:
- Handle the LS64 fault to userspace and allow userspace to inject LS64 fault
- Reorder the patches to make KVM handling prior to feature support
Link: https://lore.kernel.org/linux-arm-kernel/20250331094320.3...

Change since v1:
- Drop the support for LS64_ACCDATA
- handle the DABT of unsupported memory type after checking the memory attributes
Link: https://lore.kernel.org/linux-arm-kernel/20241202135504.1...

Marc Zyngier (2):
  KVM: arm64: Add exit to userspace on {LD,ST}64B* outside of memslots
  KVM: arm64: Add documentation for KVM_EXIT_ARM_LDST64B

Yicong Yang (5):
  KVM: arm64: Handle DABT caused by LS64* instructions on unsupported
    memory
  arm64: Provide basic EL2 setup for FEAT_{LS64, LS64_V} usage at EL0/1
  arm64: Add support for FEAT_{LS64, LS64_V}
  KVM: arm64: Enable FEAT_{LS64, LS64_V} in the supported guest
  kselftest/arm64: Add HWCAP test for FEAT_{LS64, LS64_V}

 Documentation/arch/arm64/booting.rst      | 12 +++
 Documentation/arch/arm64/elf_hwcaps.rst   | 14 ++++
 Documentation/virt/kvm/api.rst            | 43 +++++++++--
 arch/arm64/include/asm/el2_setup.h        | 12 ++-
 arch/arm64/include/asm/esr.h              |  8 ++
 arch/arm64/include/asm/hwcap.h            |  2 +
 arch/arm64/include/asm/kvm_emulate.h      |  7 ++
 arch/arm64/include/uapi/asm/hwcap.h       |  2 +
 arch/arm64/kernel/cpufeature.c            | 51 +++++++++++++
 arch/arm64/kernel/cpuinfo.c               |  2 +
 arch/arm64/kvm/inject_fault.c             | 22 ++++++
 arch/arm64/kvm/mmio.c                     | 27 ++++++-
 arch/arm64/kvm/mmu.c                      | 14 +++-
 arch/arm64/tools/cpucaps                  |  2 +
 include/uapi/linux/kvm.h                  |  3 +-
 tools/testing/selftests/arm64/abi/hwcap.c | 90 +++++++++++++++++++++++
 16 files changed, 300 insertions(+), 11 deletions(-)

-- 
2.33.0