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Re: [Xen-devel] Bootstrap in mini-os

Jayaraman, Bhaskar, le Fri 27 Jun 2008 20:50:24 +0800, a écrit :
> 1] Since the bootstrap page tables are marked read-only we have our start_pfn 
> after it?


> 2] The domain loader will load the Mini-OS at pseudo physical page 0?

All PV kernels are always loaded at PFN 0. Then PFNs are mapped at the
virtual address set in the ELF notes.

> 3] I didn't understand how does deducting &_text give a physical address,

Because _text is always at PFN 0.

> since the start pfn is to begin after pt_base and not at pseudo physical 
> address 0.

_text is not at start_pfn. start_pfn is _after_ all the day0 layout,
i.e. the kernel code, the bootstrap page table etc.

> What I'm saying is what difference will it make if we don't deduct the text 
> pseudo physical address?

It does make a difference if somebody, for some reason, wants to have
the mini-os kernel virtually start at e.g. 0xc0000000. It will still
pseudo-physically start at 0.

> 4] If I'm right the shared_info pte is overwritten by the hypervisor with the 
> shared_info struct that we pass it and relocated to another mfn in the 
> mfn_list with the hypercall? However, Mini-os will still keep referring to 
> shared_info at pseudo physical page at offset 0x1000 or the 1st pseudo 
> physical frame?

Currently the PFN numbered 1 is not available from mini-os, because it
is "overmapped" by the shared info page.


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