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xen-devel
RE: [Xen-devel] start of day mem layout
> I am working on updating the mini-os to work on XEN 2.0. I am
> currently working on the memory management part of mini-os. I am
> trying to undestand the start of day memory layout that the guest
> domain (mini-os) gets from XEN when it 1st boots up. From what I
> undestand, 4 MB of memory are already mapped and virtual memory
> from 0xC000_0000 to 0xC040_0000 (4MB) are accessible. XEN already
> allocates a pgd and ONE page table for this 4MB vritual memory
> mapping.
A worthy effort, thanks for doing this.
I can't remember this stuff off-hand, but hopefully someone who's done a
port recently will speak up.
Ian
> I am booting mini-os with 16 MB of memory and these are the
> information I get:
>
> shared_info 0xc0001000
> pfn_to_mfn 0xc0010000
> Page Global Directory 0xc0014000
> Page Table 0xc0015000
> start_info 0xc0016000
>
> Also, I think my kernel image contains some symbols such as _text,
> _etext, _edata, _end.
>
> _text 0xc0000000
> _etext 0xc0007c04
> _edata 0xc000d2c0
> _end 0x819
>
> I try to draw the virtual mem layout below. Sorry if it does not
> appear correctly because of different fonts.
>
> _edata start_info
> c000d2c0 c0016000
> shared_info | PGD |
> c0001000 | c0014000 |
> | | | |
> ------------------------------------------
> | | | | | | | |
> | | | | | | | |
> | | | | | | | |
> ------------------------------------------
> | | | |
> c0000000 | c0010000 c0015000
> _text | pfn_to_mfn PT
> |
> _etext
> c0007c04
>
> I have a few questions. If someone could give some feedback that
> would be very appreciated.
>
> I am not sure if those symbols _text, _etext, _edata and _end are
> meaningful or not, but is it correct to have the shared_info in the
> middle of my kernel image between _text and _etext ?
>
> The default control ring between domain0 and a guest OS is found
> at shared_info + 2048 offset, is that still valid ?
>
> Is there anything important after the start_info structure ?
> Is address starting at c0016000 + sizeof(start_info) available
> to use ?
>
> Also my _end symbol is found at address 0x819, so I don't quite
> udnestand that. Maybe something wrong I am doing in the linking
> process of my kernel image.
>
> Thanks
> Richard
>
>
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