UefiCpuPkg/CpuDxe: Add stackless assembly AP entry points

The AP startup code simply jumps into this code with the CpuDxe driver
without setting up a stack for the processor.

Therefore, this code must setup the stack before calling into C code.

This is the basic flow:
* AP enters CpuDxe driver code (AsmApEntryPoint) without stack
  - AP grabs a lock
  - AP sets up stack
  - AP calls CpuMp.c:ApEntryPointInC
  - If ApEntryPointInC returns, the lock is freed, and another AP may
    run
  - The AP C code may call AsmApDoneWithCommonStack to indicate that
    the AP is no longer using the stack, and another may therefore
    proceed to use the stack and then call ApEntryPointInC

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Jeff Fan <jeff.fan@intel.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@16347 6f19259b-4bc3-4df7-8a09-765794883524

UefiCpuPkg/CpuDxe/X64/MpAsm.asm

@@ -0,0 +1,76 @@
+;------------------------------------------------------------------------------
+;
+; Copyright (c) 2006 - 2014, 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.
+;
+;------------------------------------------------------------------------------
+
+#include <Base.h>
+
+extern ASM_PFX(mTopOfApCommonStack):QWORD
+extern ASM_PFX(ApEntryPointInC):PROC
+
+.data
+
+;
+; This lock only allows one AP to use the mTopOfApCommonStack stack at a time
+;
+ApStackLock:
+    dd      0
+
+.code
+
+;------------------------------------------------------------------------------
+; VOID
+; EFIAPI
+; AsmApEntryPoint (
+;   VOID
+;   );
+;------------------------------------------------------------------------------
+ASM_PFX(AsmApEntryPoint) PROC PUBLIC
+
+    cli
+AsmApEntryPointAcquireLock:
+lock bts    dword ptr [ApStackLock], 0
+    pause
+    jc      AsmApEntryPointAcquireLock
+
+    mov     rsp, [ASM_PFX(mTopOfApCommonStack)]
+    call    ASM_PFX(ApEntryPointInC)
+
+    cli
+
+lock btc    dword ptr [ApStackLock], 0
+
+    mov     eax, 100h
+AsmApEntryPointShareLock:
+    pause
+    dec     eax
+    jnz     AsmApEntryPointShareLock
+
+    jmp     ASM_PFX(AsmApEntryPoint)
+
+ASM_PFX(AsmApEntryPoint) ENDP
+
+;------------------------------------------------------------------------------
+; VOID
+; EFIAPI
+; AsmApDoneWithCommonStack (
+;   VOID
+;   );
+;------------------------------------------------------------------------------
+ASM_PFX(AsmApDoneWithCommonStack) PROC PUBLIC
+
+lock btc    dword ptr [ApStackLock], 0
+    ret
+
+ASM_PFX(AsmApDoneWithCommonStack) ENDP
+
+END
+