On Sep 6, 2014, at 11:40 AM, stanley.ganyezu <[email protected]> wrote:
> Hi Andrew,
> Do Neeraj mentioned limitation have any influence on your method?
>
>
No the SDM is defining the initial state. It is a form of big real mode. You
can still put the processor in protected mode (32-bit) and from protected mode
you can enable PAE (32-bit, uses page tables to access memory > 4GB) or
transition to Long mode (64-bit).
Thanks,
Andrew Fish
>
>
>
> Best wishes,
> Stanley
>
> 发件人: Andrew Fish [mailto:[email protected]]
> 发送时间: 2014年9月7日 1:57
> 收件人: [email protected]
> 主题: Re: [edk2] 答复: run SMM in 64-bit
>
>
> On Sep 6, 2014, at 10:50 AM, stanley.ganyezu <[email protected]>
> wrote:
>
>
> Hi Neeraj,
> Some server have multi PCI segment. These PCI segment are put above
> 4GB to save more memory space belowme
> 4GB for legacy device(some device only use 32-bit Memory Mapped IO space).My
> SMI want to access these PCI segment.
> But I can’t find a method to touch it in X64.
>
>
>
> You need to enable PAE or put the processor in Long mode to access memory >
> 4GB.
>
> Thanks,
>
> Andrew Fish
>
>
>
> Best wishes,
> Stanley
>
> 发件人: Neeraj Ladkani [mailto:[email protected]]
> 发送时间: 2014年9月7日 0:58
> 收件人: [email protected]
> 主题: Re: [edk2] run SMM in 64-bit
>
> Hi,
>
> as par SDM section 34.5.1. not sure if its a hardware limitation.
> be
>
> "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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