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/*********************************************************
* Copyright (C) 2006-2015 VMware, Inc. All rights reserved.
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as published
* by the Free Software Foundation version 2.1 and no later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the Lesser GNU General Public
* License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
*********************************************************/
/*
* atomic.c --
*
* Support for atomic instructions.
*
* This is the user-level and vmkernel version.
* The monitor-only version is in vmcore/vmm/main.
*/
#include "vmware.h"
#include "vm_atomic.h"
#if defined(__i386__) || defined(__x86_64__)
#include "x86cpuid.h"
#include "x86cpuid_asm.h"
#endif
#include "vm_basic_asm.h"
#include "vmk_exports.h"
/*
* AMD Rev E/F CPUs suffer from erratum 147 (see AMD docs). Our work-around
* is to execute a "fence" after every atomic instruction. Since this is
* expensive we conditionalize on "AtomicUseFence".
* ESX no longer supports any of the CPUs, so for SERVER builds neither
* the vmx nor the vmkernel define these variables in order to force all
* code in these (performance critical) components to use the constant
* version of AtomicUseFence from vm_atomic.h.
* For other components, we continue to define the variables to allow the
* code to work whether it is compiled with VMX86_SERVER set or not. This
* is conservative but the performance penalty should be minimal. And it
* is a (longer term) temporary sitation: when we eventually remove Rev F
* support from our hosted products, this will all go away.
*/
#if !defined(VMKERNEL) && !(defined(VMX86_VMX) && defined(VMX86_SERVER))
#undef AtomicUseFence
#undef atomicFenceInitialized
Bool AtomicUseFence;
Bool atomicFenceInitialized;
#endif
/*
*-----------------------------------------------------------------------------
*
* AtomicInitFence --
*
* Compute AtomicUseFence.
*
* This version of fence initialization doesn't take into account
* the number of CPUs. Code that cares uses Atomic_SetFence() directly.
* See Atomic_Init in vm_atomic.h.
*
* This code is rather weird because while the logic belongs
* in x86cpuid.h, it's almost impossible to put this whole function
* there, so here it is. -- edward
*
* Results:
* None.
*
* Side effects:
* As described.
*
*-----------------------------------------------------------------------------
*/
void
AtomicInitFence(void)
{
Bool needFence = FALSE;
#if MAY_NEED_AMD_REVF_WORKAROUND && (defined(__i386__) || defined(__x86_64__))
{
CPUIDRegs regs;
__GET_CPUID(0, ®s);
if (CPUID_ID0RequiresFence(®s)) {
__GET_CPUID(1, ®s);
if (CPUID_ID1RequiresFence(®s)) {
needFence = TRUE;
}
}
}
#endif
Atomic_SetFence(needFence);
}
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