Re: [Xen-devel] mapping virtual address to corresponding shadow page in xen

[Tim Deegan <tim@xxxxxxx>]

Hi, 

At 16:26 +0330 on 24 Dec (1324744009), Mohamad Rezaei wrote:
> My question is when I want to read a data from domain, I use
> copy_from_guest. but now I want to map that address in domain (guest)
> to an address inside xen (hypervisor). I need to translate that
> address. somehow like this: gva -> gpfn -> gmfn -> mfn. To do this I
> have started a dom0 with dom0_shadow=1 option. So I presume that vtx
> is enabled for dom0.

Actually shadow pagetables are quite separate from VT-x (and predate it
- they were originally used for live migratoin of PV guests).  So no,
dom0_shadow=1 doesn't turn on VT-x for dom0.

Luckily, you don't need VT-x to map a page of dom0 memory (in fact it
wouldn't help).

Have a look at mem_event_enable() in xen/arch/x86/mm/mem_event.c - it
does exactly wat you need, starting with VA ring_addr and ending with a
mapping in med->ring_page.

Cheers, 

Tim.

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