linux-kernel - [V3 09/11] tools: Add atomic_test_and_set

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Date:   Wed, 10 Aug 2022 08:20:31 -0700
From:   Peter Gonda <pgonda@...gle.com>
To:     kvm@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, marcorr@...gle.com,
        seanjc@...gle.com, michael.roth@....com, thomas.lendacky@....com,
        joro@...tes.org, mizhang@...gle.com, pbonzini@...hat.com,
        andrew.jones@...ux.dev, vannapurve@...gle.com,
        Peter Gonda <pgonda@...gle.com>
Subject: [V3 09/11] tools: Add atomic_test_and_set_bit()

atomic_test_and_set_bit() allows for atomic bitmap usage from KVM
selftests.

Signed-off-by: Peter Gonda <pgonda@...gle.com>
Suggested-by: Sean Christopherson <seanjc@...gle.com>
---
 tools/arch/x86/include/asm/atomic.h    |  7 +++++++
 tools/include/asm-generic/atomic-gcc.h | 15 +++++++++++++++
 2 files changed, 22 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..8d9b2d1768bf 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 +70,18 @@ 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)
+{
+	long old, val;
+	unsigned long mask = BIT_MASK(nr);
+
+	addr += BIT_WORD(nr);
+	val = READ_ONCE(*addr);
+	if (val & mask)
+		return 1;
+
+	old = cmpxchg(addr, val, val & mask);
+	return !!(old & mask);
+}
+
 #endif /* __TOOLS_ASM_GENERIC_ATOMIC_H */
-- 
2.37.1.559.g78731f0fdb-goog