[Xen-devel] reserve e820 ram

[Francisco Rocha <f.e.liberal-rocha@xxxxxxxxxxxxxxx>]

Hello everyone,

I am trying to reserve an area of memory using e820's reserve_e820_ram.
Everything happens as expected, but then there is something that confuses me.
I have some questions regarding it.

Why is e820 being used in arch_init_memory (xen/arch/x86/mm.c in my case) and 
not boot_e820 (the one we changed)?
I am asking because from what I understand this will make my use of 
reserve_e820_ram
useless, but I think I still not have all the information I need to know how it 
all connects.

When I try to use reserve_e820_ram on the actual e820 variable the boot process 
fails in an assertion on file xen/arch/x86/mm.c
in function share_xen_page_with_guest.
It must be because the pages I reserved are not part of the Xen heap.

To create a range that I can later use as a guest's RAM can I use dom_cow 
instead of dom_io in arch_init_memory?
Or will that create problems when allocating the pages to an unprivileged 
domain?
I don't want that memory range in use by the main memory pool used by the 
allocators.

>From what I understand. The pages must have to be assigned to a particular 
>domain, dom_xen|io|cow.
I see this as keeping them mapped and usable before assigning them to the domU 
I want. Is that thought correct?
Later I want to be able to get them, and assign them to the domU when it is 
started and gets its memory allocated.

Thank you for your time,
Francisco
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