[v3] arm64: Support FEAT_LSFE (Large System Float Extension)

[PATCH v3 0/3] arm64: Support FEAT_LSFE (Large System Float Extension)

Mark Brown posted 3 patches 1 month, 2 weeks ago

Diff against v1 v2 v4
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There is a newer version of this series

Documentation/arch/arm64/elf_hwcaps.rst   |  4 ++++
arch/arm64/include/asm/hwcap.h            |  1 +
arch/arm64/include/uapi/asm/hwcap.h       |  1 +
arch/arm64/kernel/cpufeature.c            |  2 ++
arch/arm64/kernel/cpuinfo.c               |  1 +
arch/arm64/kvm/sys_regs.c                 |  4 +++-
tools/testing/selftests/arm64/abi/hwcap.c | 21 +++++++++++++++++++++
7 files changed, 33 insertions(+), 1 deletion(-)

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[PATCH v3 0/3] arm64: Support FEAT_LSFE (Large System Float Extension)

Posted by Mark Brown 1 month, 2 weeks ago

FEAT_LSFE is optional from v9.5, it adds new instructions for atomic
memory operations with floating point values.  We have no immediate use
for it in kernel, provide a hwcap so userspace can discover it and allow
the ID register field to be exposed to KVM guests.

Signed-off-by: Mark Brown <broonie@kernel.org>
---
Changes in v3:
- Rebase onto v6.17-rc1.
- Link to v2: https://lore.kernel.org/r/20250703-arm64-lsfe-v2-0-eced80999cb4@kernel.org

Changes in v2:
- Fix result of vi dropping in hwcap test.
- Link to v1: https://lore.kernel.org/r/20250627-arm64-lsfe-v1-0-68351c4bf741@kernel.org

---
Mark Brown (3):
      arm64/hwcap: Add hwcap for FEAT_LSFE
      KVM: arm64: Expose FEAT_LSFE to guests
      kselftest/arm64: Add lsfe to the hwcaps test

 Documentation/arch/arm64/elf_hwcaps.rst   |  4 ++++
 arch/arm64/include/asm/hwcap.h            |  1 +
 arch/arm64/include/uapi/asm/hwcap.h       |  1 +
 arch/arm64/kernel/cpufeature.c            |  2 ++
 arch/arm64/kernel/cpuinfo.c               |  1 +
 arch/arm64/kvm/sys_regs.c                 |  4 +++-
 tools/testing/selftests/arm64/abi/hwcap.c | 21 +++++++++++++++++++++
 7 files changed, 33 insertions(+), 1 deletion(-)
---
base-commit: 8f5ae30d69d7543eee0d70083daf4de8fe15d585
change-id: 20250625-arm64-lsfe-0810cf98adc2

Best regards,
--  
Mark Brown <broonie@kernel.org>

Re: [PATCH v3 0/3] arm64: Support FEAT_LSFE (Large System Float Extension)

Posted by Will Deacon 2 weeks, 3 days ago

On Mon, 18 Aug 2025 20:21:17 +0100, Mark Brown wrote:
> FEAT_LSFE is optional from v9.5, it adds new instructions for atomic
> memory operations with floating point values.  We have no immediate use
> for it in kernel, provide a hwcap so userspace can discover it and allow
> the ID register field to be exposed to KVM guests.
> 
> 

Applied first patch to arm64 (for-next/cpufeature), thanks!

[1/3] arm64/hwcap: Add hwcap for FEAT_LSFE
      https://git.kernel.org/arm64/c/220928e52cb0

Cheers,
-- 
Will

https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev