[Xen-devel] [PATCH v2 07/18] OvmfPkg/XenBusDxe: Add InterlockedCompareExchange16.

[Anthony PERARD <anthony.perard@xxxxxxxxxx>]

This is a copy of InterlockedCompareExchange32 from the
BaseSynchronizationLib.

The function will be used in the next patch.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>

---
Change in V2:
- Add intel compilation code
  MSFT code is not compied over because I don't know how it works.
---
 OvmfPkg/XenBusDxe/InterlockedCompareExchange16.h   | 15 ++++++++
 .../XenBusDxe/InterlockedCompareExchange16Intel.c  | 32 +++++++++++++++++
 .../XenBusDxe/X64/InterlockedCompareExchange16.asm | 41 ++++++++++++++++++++++
 .../XenBusDxe/X64/InterlockedCompareExchange16.c   | 41 ++++++++++++++++++++++
 OvmfPkg/XenBusDxe/XenBusDxe.inf                    |  4 +++
 5 files changed, 133 insertions(+)
 create mode 100644 OvmfPkg/XenBusDxe/InterlockedCompareExchange16.h
 create mode 100644 OvmfPkg/XenBusDxe/InterlockedCompareExchange16Intel.c
 create mode 100644 OvmfPkg/XenBusDxe/X64/InterlockedCompareExchange16.asm
 create mode 100644 OvmfPkg/XenBusDxe/X64/InterlockedCompareExchange16.c

diff --git a/OvmfPkg/XenBusDxe/InterlockedCompareExchange16.h 
b/OvmfPkg/XenBusDxe/InterlockedCompareExchange16.h
new file mode 100644
index 0000000..9067882
--- /dev/null
+++ b/OvmfPkg/XenBusDxe/InterlockedCompareExchange16.h
@@ -0,0 +1,15 @@
+UINT16
+EFIAPI
+InternalSyncCompareExchange16 (
+  IN      UINT16                    *Value,
+  IN      UINT16                    CompareValue,
+  IN      UINT16                    ExchangeValue
+  );
+
+UINT16
+EFIAPI
+InterlockedCompareExchange16 (
+  IN OUT volatile  UINT16           *Value,
+  IN      UINT16                    CompareValue,
+  IN      UINT16                    ExchangeValue
+  );
diff --git a/OvmfPkg/XenBusDxe/InterlockedCompareExchange16Intel.c 
b/OvmfPkg/XenBusDxe/InterlockedCompareExchange16Intel.c
new file mode 100644
index 0000000..bb40e70
--- /dev/null
+++ b/OvmfPkg/XenBusDxe/InterlockedCompareExchange16Intel.c
@@ -0,0 +1,32 @@
+#include "InterlockedCompareExchange16.h"
+
+/**
+  Performs an atomic compare exchange operation on a 16-bit unsigned integer.
+
+  Performs an atomic compare exchange operation on the 16-bit unsigned integer
+  specified by Value.  If Value is equal to CompareValue, then Value is set to
+  ExchangeValue and CompareValue is returned.  If Value is not equal to 
CompareValue,
+  then Value is returned.  The compare exchange operation must be performed 
using
+  MP safe mechanisms.
+
+  If Value is NULL, then ASSERT().
+
+  @param  Value         A pointer to the 16-bit value for the compare exchange
+                        operation.
+  @param  CompareValue  16-bit value used in compare operation.
+  @param  ExchangeValue 16-bit value used in exchange operation.
+
+  @return The original *Value before exchange.
+
+**/
+UINT16
+EFIAPI
+InterlockedCompareExchange16 (
+  IN OUT  UINT16                    *Value,
+  IN      UINT16                    CompareValue,
+  IN      UINT16                    ExchangeValue
+  )
+{
+  ASSERT (Value != NULL);
+  return InternalSyncCompareExchange16 (Value, CompareValue, ExchangeValue);
+}
diff --git a/OvmfPkg/XenBusDxe/X64/InterlockedCompareExchange16.asm 
b/OvmfPkg/XenBusDxe/X64/InterlockedCompareExchange16.asm
new file mode 100644
index 0000000..b23e421
--- /dev/null
+++ b/OvmfPkg/XenBusDxe/X64/InterlockedCompareExchange16.asm
@@ -0,0 +1,41 @@
+;------------------------------------------------------------------------------
+;
+; Copyright (c) 2006, Intel Corporation. All rights reserved.<BR>
+; This program and the accompanying materials
+; are licensed and made available under the terms and conditions of the BSD 
License
+; which accompanies this distribution.  The full text of the license may be 
found at
+; http://opensource.org/licenses/bsd-license.php.
+;
+; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
+; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
+;
+; Module Name:
+;
+;   InterlockedCompareExchange16.Asm
+;
+; Abstract:
+;
+;   InterlockedCompareExchange16 function
+;
+; Notes:
+;
+;------------------------------------------------------------------------------
+
+    .code
+
+;------------------------------------------------------------------------------
+; UINT16
+; EFIAPI
+; InterlockedCompareExchange16 (
+;   IN      UINT16                    *Value,
+;   IN      UINT16                    CompareValue,
+;   IN      UINT16                    ExchangeValue
+;   );
+;------------------------------------------------------------------------------
+InternalSyncCompareExchange16   PROC
+    mov     eax, edx
+    lock    cmpxchg [rcx], r8w
+    ret
+InternalSyncCompareExchange16   ENDP
+
+    END
diff --git a/OvmfPkg/XenBusDxe/X64/InterlockedCompareExchange16.c 
b/OvmfPkg/XenBusDxe/X64/InterlockedCompareExchange16.c
new file mode 100644
index 0000000..64962ba
--- /dev/null
+++ b/OvmfPkg/XenBusDxe/X64/InterlockedCompareExchange16.c
@@ -0,0 +1,41 @@
+// Took from BaseSynchronizationLib, and replaced 32 by 16
+/**
+  Performs an atomic compare exchange operation on a 16-bit unsigned integer.
+
+  Performs an atomic compare exchange operation on the 16-bit unsigned integer
+  specified by Value.  If Value is equal to CompareValue, then Value is set to
+  ExchangeValue and CompareValue is returned.  If Value is not equal to 
CompareValue,
+  then Value is returned.  The compare exchange operation must be performed 
using
+  MP safe mechanisms.
+
+
+  @param  Value         A pointer to the 16-bit value for the compare exchange
+                        operation.
+  @param  CompareValue  16-bit value used in compare operation.
+  @param  ExchangeValue 16-bit value used in exchange operation.
+
+  @return The original *Value before exchange.
+
+**/
+UINT16
+EFIAPI
+InterlockedCompareExchange16 (
+  IN OUT volatile  UINT16           *Value,
+  IN      UINT16                    CompareValue,
+  IN      UINT16                    ExchangeValue
+  )
+{
+  __asm__ __volatile__ (
+    "lock                 \n\t"
+    "cmpxchgw    %3, %1       "
+    : "=a" (CompareValue),    // %0
+      "=m" (*Value)           // %1
+    : "a"  (CompareValue),    // %2
+      "r"  (ExchangeValue),   // %3 
+      "m"  (*Value)
+    : "memory",
+      "cc"
+    );
+    
+  return CompareValue;
+}
diff --git a/OvmfPkg/XenBusDxe/XenBusDxe.inf b/OvmfPkg/XenBusDxe/XenBusDxe.inf
index aed2359..612c3db 100644
--- a/OvmfPkg/XenBusDxe/XenBusDxe.inf
+++ b/OvmfPkg/XenBusDxe/XenBusDxe.inf
@@ -33,10 +33,14 @@
   ComponentName.h
   XenHypercall.c
   XenHypercall.h
+  InterlockedCompareExchange16.h
 
 [Sources.X64]
   X64/hypercall.S
   X64/hypercall.asm
+  X64/InterlockedCompareExchange16.c | GCC
+  X64/InterlockedCompareExchange16.asm | INTEL
+  InterlockedCompareExchange16Intel.c | INTEL
 
 [LibraryClasses]
   UefiDriverEntryPoint
-- 
Anthony PERARD


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