From: Kumar Kartikeya Dwivedi Date: Sun, 16 Mar 2025 04:05:30 +0000 (-0700) Subject: rqspinlock: Add basic support for CONFIG_PARAVIRT X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=ecbd8047526d3e9681043c287dea7bc67ef33eb4;p=users%2Fjedix%2Flinux-maple.git rqspinlock: Add basic support for CONFIG_PARAVIRT We ripped out PV and virtualization related bits from rqspinlock in an earlier commit, however, a fair lock performs poorly within a virtual machine when the lock holder is preempted. As such, retain the virt_spin_lock fallback to test and set lock, but with timeout and deadlock detection. We can do this by simply depending on the resilient_tas_spin_lock implementation from the previous patch. We don't integrate support for CONFIG_PARAVIRT_SPINLOCKS yet, as that requires more involved algorithmic changes and introduces more complexity. It can be done when the need arises in the future. Signed-off-by: Kumar Kartikeya Dwivedi Link: https://lore.kernel.org/r/20250316040541.108729-15-memxor@gmail.com Signed-off-by: Alexei Starovoitov --- diff --git a/arch/x86/include/asm/rqspinlock.h b/arch/x86/include/asm/rqspinlock.h new file mode 100644 index 000000000000..24a885449ee6 --- /dev/null +++ b/arch/x86/include/asm/rqspinlock.h @@ -0,0 +1,33 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_X86_RQSPINLOCK_H +#define _ASM_X86_RQSPINLOCK_H + +#include + +#ifdef CONFIG_PARAVIRT +DECLARE_STATIC_KEY_FALSE(virt_spin_lock_key); + +#define resilient_virt_spin_lock_enabled resilient_virt_spin_lock_enabled +static __always_inline bool resilient_virt_spin_lock_enabled(void) +{ + return static_branch_likely(&virt_spin_lock_key); +} + +#ifdef CONFIG_QUEUED_SPINLOCKS +typedef struct qspinlock rqspinlock_t; +#else +typedef struct rqspinlock rqspinlock_t; +#endif +extern int resilient_tas_spin_lock(rqspinlock_t *lock); + +#define resilient_virt_spin_lock resilient_virt_spin_lock +static inline int resilient_virt_spin_lock(rqspinlock_t *lock) +{ + return resilient_tas_spin_lock(lock); +} + +#endif /* CONFIG_PARAVIRT */ + +#include + +#endif /* _ASM_X86_RQSPINLOCK_H */ diff --git a/include/asm-generic/rqspinlock.h b/include/asm-generic/rqspinlock.h index 12f72c4a97cd..a837c6b6abd9 100644 --- a/include/asm-generic/rqspinlock.h +++ b/include/asm-generic/rqspinlock.h @@ -35,6 +35,20 @@ extern int resilient_tas_spin_lock(rqspinlock_t *lock); extern int resilient_queued_spin_lock_slowpath(rqspinlock_t *lock, u32 val); #endif +#ifndef resilient_virt_spin_lock_enabled +static __always_inline bool resilient_virt_spin_lock_enabled(void) +{ + return false; +} +#endif + +#ifndef resilient_virt_spin_lock +static __always_inline int resilient_virt_spin_lock(rqspinlock_t *lock) +{ + return 0; +} +#endif + /* * Default timeout for waiting loops is 0.25 seconds */ diff --git a/kernel/bpf/rqspinlock.c b/kernel/bpf/rqspinlock.c index 714dfab5caa8..ed21ee010063 100644 --- a/kernel/bpf/rqspinlock.c +++ b/kernel/bpf/rqspinlock.c @@ -352,6 +352,9 @@ int __lockfunc resilient_queued_spin_lock_slowpath(rqspinlock_t *lock, u32 val) BUILD_BUG_ON(CONFIG_NR_CPUS >= (1U << _Q_TAIL_CPU_BITS)); + if (resilient_virt_spin_lock_enabled()) + return resilient_virt_spin_lock(lock); + RES_INIT_TIMEOUT(ts); /*