Commit 9c3cef54 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Greg Kroah-Hartman
Browse files

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: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent d0a17809

include/linux/vmw_vmci_defs.h

+10 −20
Original line number Diff line number Diff line
@@ -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;

}



/*