[PATCH v5 4/7] tools: Add atomic_test_and_set_bit()

Sean Christopherson
2022-08-25T23:26:32Z

From: Peter Gonda <pgonda@google.com>

Add x86 and generic implementations of atomic_test_and_set_bit() to allow
KVM selftests to atomically manage bitmaps.

Note, the generic version is taken from arch_test_and_set_bit() as of
commit 415d83249709 ("locking/atomic: Make test_and_*_bit() ordered on
failure").

Signed-off-by: Peter Gonda <pgonda@google.com>
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
tools/arch/x86/include/asm/atomic.h | 7 +++++++
tools/include/asm-generic/atomic-gcc.h | 12 ++++++++++++
2 files changed, 19 insertions(+)

diff --git a/tools/arch/x86/include/asm/atomic.h b/tools/arch/x86/include/asm/atomic.h
index 1f5e26aae9fc..01cc27ec4520 100644
--- a/tools/arch/x86/include/asm/atomic.h
+++ b/tools/arch/x86/include/asm/atomic.h
@@ -8,6 +8,7 @@

#define LOCK_PREFIX "\n\tlock; "

+#include <asm/asm.h>
#include <asm/cmpxchg.h>

/*
@@ -70,4 +71,10 @@ static __always_inline int atomic_cmpxchg(atomic_t *v, int old, int new)
return cmpxchg(&v->counter, old, new);
}

+static inline int atomic_test_and_set_bit(long nr, unsigned long *addr)
+{
+ GEN_BINARY_RMWcc(LOCK_PREFIX __ASM_SIZE(bts), *addr, "Ir", nr, "%0", "c");
+
+}
+
#endif /* _TOOLS_LINUX_ASM_X86_ATOMIC_H */
diff --git a/tools/include/asm-generic/atomic-gcc.h b/tools/include/asm-generic/atomic-gcc.h
index 4c1966f7c77a..6daa68bf5b9e 100644
--- a/tools/include/asm-generic/atomic-gcc.h
+++ b/tools/include/asm-generic/atomic-gcc.h
@@ -4,6 +4,7 @@

#include <linux/compiler.h>
#include <linux/types.h>
+#include <linux/bitops.h>

/*
* Atomic operations that C can't guarantee us. Useful for
@@ -69,4 +70,15 @@ static inline int atomic_cmpxchg(atomic_t *v, int oldval, int newval)
return cmpxchg(&(v)->counter, oldval, newval);
}

+static inline int atomic_test_and_set_bit(long nr, unsigned long *addr)
+{
+ unsigned long mask = BIT_MASK(nr);
+ long old;
+
+ addr += BIT_WORD(nr);
+
+ old = __sync_fetch_and_or(addr, mask);
+ return !!(old & mask);
+}
+
#endif /* __TOOLS_ASM_GENERIC_ATOMIC_H */