[PATCH v4 00/13] Zacas/Zabha support and qspinlocks

Alexandre Ghiti
2024-07-31T07:24:17Z

This implements [cmp]xchgXX() macros using Zacas and Zabha extensions
and finally uses those newly introduced macros to add support for
qspinlocks: note that this implementation of qspinlocks satisfies the
forward progress guarantee.

It also uses Ziccrse to provide the qspinlock implementation.

Thanks to Guo and Leonardo for their work!

v3: https://lore.kernel.org/linux-riscv/20240717061957.140712-1-alexghiti@rivosinc.com/
v2: https://lore.kernel.org/linux-riscv/20240626130347.520750-1-alexghiti@rivosinc.com/
v1: https://lore.kernel.org/linux-riscv/20240528151052.313031-1-alexghiti@rivosinc.com/

Changes in v4:
- rename sc_sfx into sc_cas_sfx in _arch_cmpxchg (Drew)
- cmpxchg() depends on 64BIT (Drew)
- rename xX register into tX (Drew)
- cas operations require the old value in rd, make this assignment more explicit
as it seems to confuse people (Drew, Andrea)
- Fix ticket/queued configs build errors (Andrea)
- riscv_spinlock_init() is only needed for combo spinlocks but implement it
anyway to inform of the type of spinlocks used (Andrea)
- Add RB from Guo
- Add NONPORTABLE to RISCV_QUEUED_SPINLOCKS (Samuel)
- Add a link to Guo's qspinlocks results on the sophgo platform
- Reorder ZICCRSE (Samuel)
- Use riscv_has_extention_unlikely() instead of direct asm goto, which is way
cleaner and fixes the llvm 16 bug
- add dependency on RISCV_ALTERNATIVES in kconfig
- Rebase on top of 6.11, add patches to fix header circular dependency and
to fix build_bug()

Changes in v3:
- Fix patch 4 to restrict the optimization to fully ordered AMO (Andrea)
- Move RISCV_ISA_EXT_ZABHA definition to patch 4 (Andrea)
- !Zacas at build time => no CAS from Zabha too (Andrea)
- drop patch 7 "riscv: Improve amoswap.X use in xchg()" (Andrea)
- Switch lr/sc and cas order (Guo)
- Combo spinlocks do not depend on Zabha
- Add a Kconfig for ticket/queued/combo (Guo)
- Use Ziccrse (Guo)

Changes in v2:
- Add patch for Zabha dtbinding (Conor)
- Fix cmpxchg128() build warnings missed in v1
- Make arch_cmpxchg128() fully ordered
- Improve Kconfig help texts for both extensions (Conor)
- Fix Makefile dependencies by requiring TOOLCHAIN_HAS_XXX (Nathan)
- Fix compilation errors when the toolchain does not support the
extensions (Nathan)
- Fix C23 warnings about label at the end of coumpound statements (Nathan)
- Fix Zabha and !Zacas configurations (Andrea)
- Add COMBO spinlocks (Guo)
- Improve amocas fully ordered operations by using .aqrl semantics and
removing the fence rw, rw (Andrea)
- Rebase on top "riscv: Fix fully ordered LR/SC xchg[8|16]() implementations"
- Add ARCH_WEAK_RELEASE_ACQUIRE (Andrea)
- Remove the extension version in march for LLVM since it is only required
for experimental extensions (Nathan)
- Fix cmpxchg128() implementation by adding both registers of a pair
in the list of input/output operands

Alexandre Ghiti (11):
riscv: Move cpufeature.h macros into their own header
riscv: Do not fail to build on byte/halfword operations with Zawrs
riscv: Implement cmpxchg32/64() using Zacas
dt-bindings: riscv: Add Zabha ISA extension description
riscv: Implement cmpxchg8/16() using Zabha
riscv: Improve zacas fully-ordered cmpxchg()
riscv: Implement arch_cmpxchg128() using Zacas
riscv: Implement xchg8/16() using Zabha
riscv: Add ISA extension parsing for Ziccrse
dt-bindings: riscv: Add Ziccrse ISA extension description
riscv: Add qspinlock support

Guo Ren (2):
asm-generic: ticket-lock: Reuse arch_spinlock_t of qspinlock
asm-generic: ticket-lock: Add separate ticket-lock.h

.../devicetree/bindings/riscv/extensions.yaml | 12 +
.../locking/queued-spinlocks/arch-support.txt | 2 +-
arch/riscv/Kconfig | 64 +++++
arch/riscv/Makefile | 6 +
arch/riscv/include/asm/Kbuild | 4 +-
arch/riscv/include/asm/cmpxchg.h | 264 ++++++++++++------
arch/riscv/include/asm/cpufeature-macros.h | 66 +++++
arch/riscv/include/asm/cpufeature.h | 56 +---
arch/riscv/include/asm/hwcap.h | 2 +
arch/riscv/include/asm/spinlock.h | 43 +++
arch/riscv/kernel/cpufeature.c | 2 +
arch/riscv/kernel/setup.c | 38 +++
include/asm-generic/qspinlock.h | 2 +
include/asm-generic/spinlock.h | 87 +-----
include/asm-generic/spinlock_types.h | 12 +-
include/asm-generic/ticket_spinlock.h | 105 +++++++
16 files changed, 533 insertions(+), 232 deletions(-)
create mode 100644 arch/riscv/include/asm/cpufeature-macros.h
create mode 100644 arch/riscv/include/asm/spinlock.h
create mode 100644 include/asm-generic/ticket_spinlock.h

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2.39.2