Re: [Qemu-discuss] Qemu-system-sparc: What would I need to change to add functionality to save the nvram content between boots ?

[Bodo Eggert]

On Sun, 13 Sep 2015, Programmingkid wrote:
> On Sep 13, 2015, at 5:50 PM, Bodo Eggert wrote:
> > On Sun, 13 Sep 2015, Mark Cave-Ayland wrote:
> >> On 11/09/15 19:01, Programmingkid wrote:

> >>> Mark, do you think it is possible for a QEMU command line option to
> >>> actually load the
> >>> saved OpenBIOS settings from a file and restore them into memory? I'm
> >>> thinking something
> >>> along the lines of -prom-memory <file name>. 
> > 
> >>> From memory the reason this hasn't been done is because the NVRAM
> >> interface is used across multiple architectures and there hasn't been a
> >> solution devised that would work well enough for all of them. Then again
> >> as the BIOSs involved have continued to develop, it may be now that some
> >> of the issues can now be solved so it never hurts to ask on the -devel 
> >> list.
> > 
> > I'm wondering, why wouldn't it be enough to memmap a nvram file instead of 
> > mallocing (or whatever) the memory area?
> 
> What advantage does mmap() have over malloc()? I think malloc() is a lot more
> familiar to use than mmap().

The advantage is that it's file-backed (optionally, but intended here).  
Everything you write into that memory area will be automatically 
saved and restored just like a nvram should be. At least, that's what the 
documentation promises, I never used it myself, therefore I ask.