This atomically test and clear a bit.
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Anthony PERARD <anthony.per...@citrix.com>
---
OvmfPkg/XenbusDxe/X64/TestAndClearBit.S | 10 ++++++++++
OvmfPkg/XenbusDxe/XenbusDxe.h | 11 +++++++++++
OvmfPkg/XenbusDxe/XenbusDxe.inf | 1 +
3 files changed, 22 insertions(+)
create mode 100644 OvmfPkg/XenbusDxe/X64/TestAndClearBit.S
diff --git a/OvmfPkg/XenbusDxe/X64/TestAndClearBit.S
b/OvmfPkg/XenbusDxe/X64/TestAndClearBit.S
new file mode 100644
index 0000000..e266f68
--- /dev/null
+++ b/OvmfPkg/XenbusDxe/X64/TestAndClearBit.S
@@ -0,0 +1,10 @@
+# TestAndClearBit (
+# IN INT32 Bit, // rcx
+# IN volatile VOID* Address // rdx
+# );
+ASM_GLOBAL ASM_PFX(TestAndClearBit)
+ASM_PFX(TestAndClearBit):
+ lock
+ btrl %ecx, (%rdx)
+ sbbl %eax, %eax
+ ret
diff --git a/OvmfPkg/XenbusDxe/XenbusDxe.h b/OvmfPkg/XenbusDxe/XenbusDxe.h
index 975fb6b..50d0925 100644
--- a/OvmfPkg/XenbusDxe/XenbusDxe.h
+++ b/OvmfPkg/XenbusDxe/XenbusDxe.h
@@ -94,4 +94,15 @@ struct _XENBUS_DEVICE {
shared_info_t *SharedInfo;
};
+/*
+ * Helpers
+ */
+
+INT32
+EFIAPI
+TestAndClearBit (
+ IN INT32 Bit,
+ IN volatile VOID *Address
+ );
+
#endif
diff --git a/OvmfPkg/XenbusDxe/XenbusDxe.inf b/OvmfPkg/XenbusDxe/XenbusDxe.inf
index d4007db..dc27c13 100644
--- a/OvmfPkg/XenbusDxe/XenbusDxe.inf
+++ b/OvmfPkg/XenbusDxe/XenbusDxe.inf
@@ -43,6 +43,7 @@
X64/hypercall.S
X64/hypercall.asm
X64/InterlockedCompareExchange16.c | GCC
+ X64/TestAndClearBit.S
[LibraryClasses]
UefiDriverEntryPoint
--
Anthony PERARD
------------------------------------------------------------------------------
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