[PATCH v5 0/7] Add support for FEAT_{LS64, LS64_V} and related tests

[Yicong Yang]

a gentle ping...

hi Marc and Oliver,

the discussion since v2 are mainly about the LS64 fault hanlding by kvm/hypervisor,
does this version a proper one to go ahead?

thanks.

On 2025/8/18 14:47, Yicong Yang wrote:
> From: Yicong Yang <yangyicong at hisilicon.com>
> 
> 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.
> 
> [1] https://lore.kernel.org/linux-arm-kernel/20240815125959.2097734-1-maz@kernel.org/
> 
> Tested with updated hwcap test:
> [root at localhost tmp]# dmesg | grep "All CPU(s) started"
> [   14.789859] CPU: All CPU(s) started at EL2
> [root at localhost tmp]# ./hwcap
> # LS64 present
> ok 217 cpuinfo_match_LS64
> ok 218 sigill_LS64
> ok 219 # SKIP sigbus_LS64_V
> # LS64_V present
> ok 220 cpuinfo_match_LS64_V
> ok 221 sigill_LS64_V
> ok 222 # SKIP sigbus_LS64_V
> # 115 skipped test(s) detected. Consider enabling relevant config options to improve coverage.
> # Totals: pass:107 fail:0 xfail:0 xpass:0 skip:115 error:0
> 
> root at localhost:/mnt# dmesg | grep "All CPU(s) started"
> [    0.281152] CPU: All CPU(s) started at EL1
> root at localhost:/mnt# ./hwcap
> # LS64 present
> ok 217 cpuinfo_match_LS64
> ok 218 sigill_LS64
> ok 219 # SKIP sigbus_LS64
> # LS64_V present
> ok 220 cpuinfo_match_LS64_V
> ok 221 sigill_LS64_V
> ok 222 # SKIP sigbus_LS64_V
> # 115 skipped test(s) detected. Consider enabling relevant config options to improve coverage.
> # Totals: pass:107 fail:0 xfail:0 xpass:0 skip:115 error:0
> 
> Change since v4:
> - Rebase on v6.17-rc2 and fix the conflicts
> Link: https://lore.kernel.org/linux-arm-kernel/20250715081356.12442-1-yangyicong@huawei.com/
> 
> Change since v3:
> - Inject DABT fault for LS64 fault on unsupported memory but with valid memslot
> Link: https://lore.kernel.org/linux-arm-kernel/20250626080906.64230-1-yangyicong@huawei.com/
> 
> 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/20250331094320.35226-1-yangyicong@huawei.com/
> 
> 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/20241202135504.14252-1-yangyicong@huawei.com/
> 
> 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   |  6 ++
>  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, 292 insertions(+), 11 deletions(-)
>