Commit bb056c0f authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
Browse files

tools: KVM: selftests: Convert clear/set_bit() to actual atomics 



Convert {clear,set}_bit() to atomics as KVM's ucall implementation relies
on clear_bit() being atomic, they are defined in atomic.h, and the same
helpers in the kernel proper are atomic.

KVM's ucall infrastructure is the only user of clear_bit() in tools/, and
there are no true set_bit() users.  tools/testing/nvdimm/ does make heavy
use of set_bit(), but that code builds into a kernel module of sorts, i.e.
pulls in all of the kernel's header and so is already getting the kernel's
atomic set_bit().

Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Message-Id: <20221119013450.2643007-10-seanjc@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 36293352

tools/arch/x86/include/asm/atomic.h

+5 −0
Original line number Diff line number Diff line
@@ -76,4 +76,9 @@ static inline int test_and_set_bit(long nr, unsigned long *addr) 
	GEN_BINARY_RMWcc(LOCK_PREFIX __ASM_SIZE(bts), *addr, "Ir", nr, "%0", "c");

}



static inline int test_and_clear_bit(long nr, unsigned long *addr)

{

	GEN_BINARY_RMWcc(LOCK_PREFIX __ASM_SIZE(btc), *addr, "Ir", nr, "%0", "c");

}



#endif /* _TOOLS_LINUX_ASM_X86_ATOMIC_H */

tools/include/asm-generic/atomic-gcc.h

+11 −0
Original line number Diff line number Diff line
@@ -81,4 +81,15 @@ static inline int test_and_set_bit(long nr, unsigned long *addr) 
	return !!(old & mask);

}



static inline int test_and_clear_bit(long nr, unsigned long *addr)

{

	unsigned long mask = BIT_MASK(nr);

	long old;



	addr += BIT_WORD(nr);



	old = __sync_fetch_and_and(addr, ~mask);

	return !!(old & mask);

}



#endif /* __TOOLS_ASM_GENERIC_ATOMIC_H */

tools/include/asm-generic/bitops/atomic.h

+6 −9
Original line number Diff line number Diff line
@@ -5,14 +5,11 @@ 
#include <asm/types.h>

#include <asm/bitsperlong.h>



static inline void set_bit(unsigned long nr, unsigned long *addr)

{

	addr[nr / __BITS_PER_LONG] |= 1UL << (nr % __BITS_PER_LONG);

}



static inline void clear_bit(unsigned long nr, unsigned long *addr)

{

	addr[nr / __BITS_PER_LONG] &= ~(1UL << (nr % __BITS_PER_LONG));

}

/*

 * Just alias the test versions, all of the compiler built-in atomics "fetch",

 * and optimizing compile-time constants on x86 isn't worth the complexity.

 */

#define set_bit test_and_set_bit

#define clear_bit test_and_clear_bit



#endif /* _TOOLS_LINUX_ASM_GENERIC_BITOPS_ATOMIC_H_ */