Hi,
as par SDM section 34.5.1. not sure if its a hardware limitation.
"After saving the current context of the processor, the processor
initializes its core registers to the values shown in Table 34-4. Upon
entering SMM, the PE and PG flags in control register CR0 are cleared,
which places the processor
in an environment similar to real-address mode. The differences between the
SMM execution environment and the
real-address mode execution environment are as follows:
• The addressable address space ranges from 0 to FFFFFFFFH (4 GBytes).
• The normal 64-KByte segment limit for real-address mode is increased to 4
GBytes.
• The default operand and address sizes are set to 16 bits, which restricts
the addressable SMRAM address space
to the 1-MByte real-address mode limit for native real-address-mode code.
However, operand-size and
address-size override prefixes can be used to access the address space
beyond the 1-MByte.
I am just curious, what kind of limitations you are facing in 4 GB limit?
Neeraj
On Sat, Sep 6, 2014 at 10:08 PM, Andrew Fish <[email protected]> wrote:
>
> On Sep 6, 2014, at 3:52 AM, stanley.ganyezu <[email protected]>
> wrote:
>
> Hi Experts,
> Currently, X86 cpu run SMM in 32-bit. There are a lot of
> limitation about 32-bit. I want to run SMM in 64-bit to access whole cpu
> address space，but I can’t figure it out.
>
>
> UEFI/PI systems run SMM in 64-bit mode? See UEFI Platform Initialization
> Specification Version 1.3. http://www.uefi.org/specifications
>
> Can you give me some tips? Any suggestion will be appreciated.
>
>
>
>
> Put the system in Long mode, this requires page tables. The DXE IPL and
> 64-bit SEC in Ovmf both have code that transitions to 64-bit long mode.
>
> https://svn.code.sf.net/p/edk2/code/trunk/edk2/MdeModulePkg/Core/DxeIplPeim/
> https://svn.code.sf.net/p/edk2/code/trunk/edk2/OvmfPkg/ResetVector/
>
> It is really dangerous to modify the SMM code if you do not fully
> understand it, since SMM runs at a higher privilege than the OS it is an
> attack point that the OS can not defend against.
>
> Thanks,
>
> Andrew Fish
>
>
>
>
>
>
> Best wishes,
> Stanley
>
>
>
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--
Thanks
Neeraj
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