diff options
Diffstat (limited to 'arch/arm64/kvm/hyp/include/nvhe/spinlock.h')
-rw-r--r-- | arch/arm64/kvm/hyp/include/nvhe/spinlock.h | 125 |
1 files changed, 125 insertions, 0 deletions
diff --git a/arch/arm64/kvm/hyp/include/nvhe/spinlock.h b/arch/arm64/kvm/hyp/include/nvhe/spinlock.h new file mode 100644 index 0000000000..7c7ea8c554 --- /dev/null +++ b/arch/arm64/kvm/hyp/include/nvhe/spinlock.h @@ -0,0 +1,125 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * A stand-alone ticket spinlock implementation for use by the non-VHE + * KVM hypervisor code running at EL2. + * + * Copyright (C) 2020 Google LLC + * Author: Will Deacon <will@kernel.org> + * + * Heavily based on the implementation removed by c11090474d70 which was: + * Copyright (C) 2012 ARM Ltd. + */ + +#ifndef __ARM64_KVM_NVHE_SPINLOCK_H__ +#define __ARM64_KVM_NVHE_SPINLOCK_H__ + +#include <asm/alternative.h> +#include <asm/lse.h> +#include <asm/rwonce.h> + +typedef union hyp_spinlock { + u32 __val; + struct { +#ifdef __AARCH64EB__ + u16 next, owner; +#else + u16 owner, next; +#endif + }; +} hyp_spinlock_t; + +#define __HYP_SPIN_LOCK_INITIALIZER \ + { .__val = 0 } + +#define __HYP_SPIN_LOCK_UNLOCKED \ + ((hyp_spinlock_t) __HYP_SPIN_LOCK_INITIALIZER) + +#define DEFINE_HYP_SPINLOCK(x) hyp_spinlock_t x = __HYP_SPIN_LOCK_UNLOCKED + +#define hyp_spin_lock_init(l) \ +do { \ + *(l) = __HYP_SPIN_LOCK_UNLOCKED; \ +} while (0) + +static inline void hyp_spin_lock(hyp_spinlock_t *lock) +{ + u32 tmp; + hyp_spinlock_t lockval, newval; + + asm volatile( + /* Atomically increment the next ticket. */ + ARM64_LSE_ATOMIC_INSN( + /* LL/SC */ +" prfm pstl1strm, %3\n" +"1: ldaxr %w0, %3\n" +" add %w1, %w0, #(1 << 16)\n" +" stxr %w2, %w1, %3\n" +" cbnz %w2, 1b\n", + /* LSE atomics */ +" mov %w2, #(1 << 16)\n" +" ldadda %w2, %w0, %3\n" + __nops(3)) + + /* Did we get the lock? */ +" eor %w1, %w0, %w0, ror #16\n" +" cbz %w1, 3f\n" + /* + * No: spin on the owner. Send a local event to avoid missing an + * unlock before the exclusive load. + */ +" sevl\n" +"2: wfe\n" +" ldaxrh %w2, %4\n" +" eor %w1, %w2, %w0, lsr #16\n" +" cbnz %w1, 2b\n" + /* We got the lock. Critical section starts here. */ +"3:" + : "=&r" (lockval), "=&r" (newval), "=&r" (tmp), "+Q" (*lock) + : "Q" (lock->owner) + : "memory"); +} + +static inline void hyp_spin_unlock(hyp_spinlock_t *lock) +{ + u64 tmp; + + asm volatile( + ARM64_LSE_ATOMIC_INSN( + /* LL/SC */ + " ldrh %w1, %0\n" + " add %w1, %w1, #1\n" + " stlrh %w1, %0", + /* LSE atomics */ + " mov %w1, #1\n" + " staddlh %w1, %0\n" + __nops(1)) + : "=Q" (lock->owner), "=&r" (tmp) + : + : "memory"); +} + +static inline bool hyp_spin_is_locked(hyp_spinlock_t *lock) +{ + hyp_spinlock_t lockval = READ_ONCE(*lock); + + return lockval.owner != lockval.next; +} + +#ifdef CONFIG_NVHE_EL2_DEBUG +static inline void hyp_assert_lock_held(hyp_spinlock_t *lock) +{ + /* + * The __pkvm_init() path accesses protected data-structures without + * holding locks as the other CPUs are guaranteed to not enter EL2 + * concurrently at this point in time. The point by which EL2 is + * initialized on all CPUs is reflected in the pkvm static key, so + * wait until it is set before checking the lock state. + */ + if (static_branch_likely(&kvm_protected_mode_initialized)) + BUG_ON(!hyp_spin_is_locked(lock)); +} +#else +static inline void hyp_assert_lock_held(hyp_spinlock_t *lock) { } +#endif + +#endif /* __ARM64_KVM_NVHE_SPINLOCK_H__ */ |