unlock SMRAM of AMD Processor

1. Unlocking 0 bit of HWCR register (MSR 0xC001_0015) in BIOS

2. Checking the SMM_BASE, and disable ASeg bit (0 bit)

SMM_BASE (MSR 0xC0010111h): check smm base if it is 0xa0000

SMM_MASK (MSR 0xC001_0113h): disable ASeg for unlocking SMRAM

3. Set MtrrFixDramModEn (bit 19) in SYSCFG register (MSR 0xC001_0010h)

It enables modification of RdDram and WrDram bits in fixed MTRRs 

4. Set the RdMem (bit 4) and WrMem (bit 3) bits of Memory Range Type Reigster MTRRfix16K_A0000 (MSR: 0x259)

msr.lo=0x18181818

msr.hi=0x18181818

5. Set the  MtrrFixDramEn (bit 18) in SYSCFG register (MSR 0xC001_0010h)

It enables read and write to RAM physical memory instead I/O mapped memory

6. Copy the binary code to 0xa0000

7. Enable the Aseg bit (0 bit) in SMM_MASK register (MSR 0xC001_0113h)

Reference: 

BKDG of AMD K8

step 4 needs to ee the “Memory Type Range Registers” section in Volume 2 of the AMD64 Architecture Programmer’s Manual for more information.

http://support.amd.com/us/Processor_TechDocs/24593_APM_v2.pdf


Ignore the above steps, use the updated version: 

First, you need an unlocked SMRAM, which means 0 bit of HWCR register is not set (MSR 0xC001_0015h)

1. Enable bit 19 and bit 18 of SYSCFG register (MSR 0xC001_0010h)
In my machine, the original value is 0x160601, and I set it to 0x1e0601

2. Set bit 4 and bit 3 of MTRR memory type range register (MSR: 0x259)
msr.lo=0x18181818
msr.hi=0x18181818
In my machine, the original value is 0, and I set it to 0x1818181818181818

3. clear bit 0 of SMM_MASK register (MSR: 0xC001_0113h)
In my machine, the original value is 1, and I set it to 0.