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8-58 Vol. 3
MULTIPLE-PROCESSOR MANAGEMENT
unsigned char MaxLPIDsPerPackage(void)
{
if (!HWMTSupported()) return 1;
execute cpuid with eax = 1
store returned value of ebx
return (unsigned char) ((reg_ebx & NUM_LOGICAL_BITS) >> 16);
}
b. Find the size of address space for processor cores in a physical processor package.
// Returns the max number of addressable IDs for processor cores in a physical processor package;
// Software should not assume cpuid reports this value to be a power of 2.
unsigned MaxCoreIDsPerPackage(void)
{
if (!HWMTSupported()) return (unsigned char) 1;
if cpuid supports leaf number 4
{ // we can retrieve multi-core topology info using leaf 4
execute cpuid with eax = 4, ecx = 0
store returned value of eax
return (unsigned) ((reg_eax >> 26) +1);
}
else // must be a single-core processor
return 1;
}
c. Query the initial APIC ID of a logical processor.
#define INITIAL_APIC_ID_BITS 0xFF000000 // CPUID.1.EBX[31:24] initial APIC ID
// Returns the 8-bit unique initial APIC ID for the processor running the code.
// Software can use OS services to affinitize the current thread to each logical processor
// available under the OS to gather the initial APIC_IDs for each logical processor.
unsigned GetInitAPIC_ID (void)
{
unsigned int reg_ebx = 0;
execute cpuid with eax = 1
store returned value of ebx
return (unsigned) ((reg_ebx & INITIAL_APIC_ID_BITS) >> 24;
}
d. Find the width of an extraction bitmask from the maximum count of the bit-field
(address size).