x2apic.c

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/*
 * PROJECT:     ReactOS Hardware Abstraction Layer
 * LICENSE:     MIT (https://spdx.org/licenses/MIT)
 * PURPOSE:     x2APIC detection and mode enable
 * COPYRIGHT:   Copyright 2026 Alex Mendoza <05alex.mendozaa@gmail.com>
 */
 
/* INCLUDES *******************************************************************/
 
#include <hal.h>
#include <x86x64/Cpuid.h>
#include "x2apicp.h"
 
#define NDEBUG
#include <debug.h>
 
/* FUNCTIONS ******************************************************************/
 
BOOLEAN
NTAPI
X2ApicIsSupported(VOID)
{
    CPUID_VERSION_INFO_REGS VersionInfo;
 
    __cpuid(VersionInfo.AsInt32, CPUID_VERSION_INFO);
 
    return VersionInfo.Ecx.Bits.x2APIC != 0;
}
 
 
VOID
NTAPI
X2ApicEnable(VOID)
{
    X2APIC_BASE_ADDRESS_REGISTER BaseRegister;
 
    BaseRegister.LongLong = __readmsr(MSR_APIC_BASE);
 
    /* xAPIC (Enable) must already be set before x2APIC can be enabled */
    BaseRegister.Enable = 1;
    BaseRegister.EnableX2Apic = 1;
 
    __writemsr(MSR_APIC_BASE, BaseRegister.LongLong);
}