RE: [Xen-devel] [PATCH][RESEND]Nvram patch for IA64

["Yu, Ke" <ke.yu@xxxxxxxxx>]

Ian Pratt  write on 2006年10月30日 17:58:
>> Do you have comments on this patch? NVRAM is a useful feature for
>> IA64 VT-I domain, especially for windows 2003 booting.
> 
> What does it use the NVRAM for? Is the meaning common across all OSes
> that use it? How many bytes are used? Does the data actually need to
> be changed, or would initializing it to a constant work?  

NVRAM is used by IA64 guest firmware (EFI) to store non-volatile variable. EFI 
variable is a concept similar to the linux bash environment variable. EFI and 
OS (Linux, Windows 2003, Windows Vista) use variable to communicate 
information. They all use EFI interface GetVariable()/SetVariable() to handle 
variable. One usage example is: to boot Windows 2003, we need run an efi tool 
"nvrboot" to import boot option into one variable, then EFI boot manager can 
read this variable and boot windows 2003.  Without NVRAM support, we must run 
nvrboot everytime creating VT-I windows 2003 domain. with NVRAM support, 
nvrboot only need to run once. This is especially useful for nightly test. 

The size of NVRAM is implementation specific. EFI spec does not define that. In 
current implementation, it is 64KB. The data is dynamically changed, per EFI or 
guest OS SetVariable() request. 

> 
> If the data is static, I'm wandering whether it would be better to
> store this data explicitly as part of the domain config rather than
> referencing another file.  
> 
> Thanks,
> Ian
> 
The data is dynamic, so I am afraid it is hard to store NVRAM data in domain 
config.

Best Regards
Ke

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