The MCRS method returns a 64-bit memory range descriptor. The
calculation is supposed to be done as follows:
max = min + len - 1
However, every operand is represented not as a QWORD but as combination
of two DWORDs for high and low part. Till now, the calculation was done
this way, please see also inline comments:
max.lo = min.lo + len.lo //this may overflow, need to carry over to high
max.hi = min.hi + len.hi
max.hi = max.hi - 1 // subtraction needs to happen on the low part
This calculation has been corrected the following way:
max.lo = min.lo + len.lo
max.hi = min.hi + len.hi + (max.lo < min.lo) // check for overflow
max.lo = max.lo - 1 // subtract from low part
The relevant part from the generated ASL for the MCRS method:
```
Method (MCRS, 1, Serialized)
{
Acquire (MLCK, 0xFFFF)
\_SB.MHPC.MSEL = Arg0
Name (MR64, ResourceTemplate ()
{
QWordMemory (ResourceProducer, PosDecode, MinFixed, MaxFixed, Cacheable, ReadWrite,
0x0000000000000000, // Granularity
0x0000000000000000, // Range Minimum
0xFFFFFFFFFFFFFFFE, // Range Maximum
0x0000000000000000, // Translation Offset
0xFFFFFFFFFFFFFFFF, // Length
,, _Y00, AddressRangeMemory, TypeStatic)
})
CreateQWordField (MR64, \_SB.MHPC.MCRS._Y00._MIN, MINL) // _MIN: Minimum Base Address
CreateDWordField (MR64, 0x12, MINH)
CreateQWordField (MR64, \_SB.MHPC.MCRS._Y00._MAX, MAXL) // _MAX: Maximum Base Address
CreateDWordField (MR64, 0x1A, MAXH)
CreateQWordField (MR64, \_SB.MHPC.MCRS._Y00._LEN, LENL) // _LEN: Length
CreateDWordField (MR64, 0x2A, LENH)
MINL = \_SB.MHPC.MHBL
MINH = \_SB.MHPC.MHBH
LENL = \_SB.MHPC.MHLL
LENH = \_SB.MHPC.MHLH
MAXL = (MINL + LENL) /* \_SB_.MHPC.MCRS.LENL */
MAXH = (MINH + LENH) /* \_SB_.MHPC.MCRS.LENH */
If ((MAXL < MINL))
{
MAXH += One /* \_SB_.MHPC.MCRS.MAXH */
}
MAXL -= One
Release (MLCK)
Return (MR64) /* \_SB_.MHPC.MCRS.MR64 */
}
```
Fixes#1800.
Signed-off-by: Anatol Belski <anbelski@linux.microsoft.com>
Both changes aim to document the absence of the CPU hot-remove
functionality on Windows.
Closes#2457.
Signed-off-by: Anatol Belski <anbelski@linux.microsoft.com>
This changeset extends the documentation with the UEFI and Windows
related info. The focus is on providing consumer with a minimum
necessary and proper piece of the information to enter the features
quickly. While UEFI is a cross platform topic, it is a required
prerequisite for the Windows usage.
Signed-off-by: Anatol Belski <anbelski@linux.microsoft.com>
