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Vol. 3 8-59
MULTIPLE-PROCESSOR MANAGEMENT
// Returns the mask bit width of a bit field from the maximum count that bit field can represent.
// This algorithm does not assume ‘address size’ to have a value equal to power of 2.
// Address size for SMT_ID can be calculated from MaxLPIDsPerPackage()/MaxCoreIDsPerPackage()
// Then use the routine below to derive the corresponding width of SMT extraction bitmask
// Address size for CORE_ID is MaxCoreIDsPerPackage(),
// Derive the bitwidth for CORE extraction mask similarly
unsigned FindMaskWidth(Unsigned Max_Count)
{unsigned int mask_width, cnt = Max_Count;
__asm {
mov eax, cnt
mov ecx, 0
mov mask_width, ecx
dec eax
bsr cx, ax
jz next
inc cx
mov mask_width, ecx
next:
mov eax, mask_width
}
return mask_width;
}
e. Extract a sub ID from an 8-bit full ID, using address size of the sub ID and shift
count.
// The routine below can extract SMT_ID, CORE_ID, and PACKAGE_ID respectively from the init
APIC_ID
// To extract SMT_ID, MaxSubIDvalue is set to the address size of SMT_ID, Shift_Count = 0
// To extract CORE_ID, MaxSubIDvalue is the address size of CORE_ID, Shift_Count is width of SMT
extraction bitmask.
// Returns the value of the sub ID, this is not a zero-based value
Unsigned char GetSubID(unsigned char Full_ID, unsigned char MaxSubIDvalue, unsigned char
Shift_Count)
{
MaskWidth = FindMaskWidth(MaxSubIDValue);
MaskBits = ((uchar) (0xff << Shift_Count)) ^ ((uchar) (0xff << Shift_Count + MaskWidth)) ;
SubID = Full_ID & MaskBits;
Return SubID;
}