From 9c3cef54c50d93871eaa46c28a06de8bd03fab63 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Thu, 6 Jun 2019 11:34:28 +0200 Subject: [PATCH] VMCI: Fixup atomic64_t abuse The VMCI driver is abusing atomic64_t and atomic_t, there is no actual atomic RmW operations around. Rewrite the code to use a regular u64 with READ_ONCE() and WRITE_ONCE() and a cast to 'unsigned long'. This fully preserves whatever broken there was (it's not endian-safe for starters, and also looks to be missing ordering). Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Greg Kroah-Hartman --- include/linux/vmw_vmci_defs.h | 30 ++++++++++-------------------- 1 file changed, 10 insertions(+), 20 deletions(-) diff --git a/include/linux/vmw_vmci_defs.h b/include/linux/vmw_vmci_defs.h index 0c06178..8ee4721 100644 --- a/include/linux/vmw_vmci_defs.h +++ b/include/linux/vmw_vmci_defs.h @@ -438,8 +438,8 @@ enum { struct vmci_queue_header { /* All fields are 64bit and aligned. */ struct vmci_handle handle; /* Identifier. */ - atomic64_t producer_tail; /* Offset in this queue. */ - atomic64_t consumer_head; /* Offset in peer queue. */ + u64 producer_tail; /* Offset in this queue. */ + u64 consumer_head; /* Offset in peer queue. */ }; /* @@ -740,13 +740,9 @@ static inline void *vmci_event_data_payload(struct vmci_event_data *ev_data) * prefix will be used, so correctness isn't an issue, but using a * 64bit operation still adds unnecessary overhead. */ -static inline u64 vmci_q_read_pointer(atomic64_t *var) +static inline u64 vmci_q_read_pointer(u64 *var) { -#if defined(CONFIG_X86_32) - return atomic_read((atomic_t *)var); -#else - return atomic64_read(var); -#endif + return READ_ONCE(*(unsigned long *)var); } /* @@ -755,23 +751,17 @@ static inline u64 vmci_q_read_pointer(atomic64_t *var) * never exceeds a 32bit value in this case. On 32bit SMP, using a * locked cmpxchg8b adds unnecessary overhead. */ -static inline void vmci_q_set_pointer(atomic64_t *var, - u64 new_val) +static inline void vmci_q_set_pointer(u64 *var, u64 new_val) { -#if defined(CONFIG_X86_32) - return atomic_set((atomic_t *)var, (u32)new_val); -#else - return atomic64_set(var, new_val); -#endif + /* XXX buggered on big-endian */ + WRITE_ONCE(*(unsigned long *)var, (unsigned long)new_val); } /* * Helper to add a given offset to a head or tail pointer. Wraps the * value of the pointer around the max size of the queue. */ -static inline void vmci_qp_add_pointer(atomic64_t *var, - size_t add, - u64 size) +static inline void vmci_qp_add_pointer(u64 *var, size_t add, u64 size) { u64 new_val = vmci_q_read_pointer(var); @@ -848,8 +838,8 @@ static inline void vmci_q_header_init(struct vmci_queue_header *q_header, const struct vmci_handle handle) { q_header->handle = handle; - atomic64_set(&q_header->producer_tail, 0); - atomic64_set(&q_header->consumer_head, 0); + q_header->producer_tail = 0; + q_header->consumer_head = 0; } /* -- 2.7.4