Re: [Xen-users] ARM: Xen on Vexpress

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2014-06-12 at 10:44 +0100, Jeenu Viswambharan wrote:
> On Wed, Jun 11, 2014 at 17:36:02, Ian Campbell wrote:
> > On Wed, 2014-06-11 at 17:28 +0100, Jeenu Viswambharan wrote:
> > > On Wed, Jun 11, 2014 at 17:24:49, Ian Campbell wrote:
> > > > It's all the Xen output from before this which I am interested in.
> > > > Since that answers the questions I have about where Xen has placed
> > > > guest RAM etc.
> > >
> > > OK, Xen logs attached.
> >
> > Thanks. These contain:
> >
> > (XEN) Populate P2M 0xa8000000->0xb0000000 (1:1 mapping for dom0)
> > (XEN) Loading kernel from boot module 2
> > (XEN) Loading zImage from 00000000a0008000 to 
> > 00000000afc00000-00000000aff26fb8
> > (XEN) Loading dom0 DTB to 0x00000000afa00000-0x00000000afa02f10
> >
> > In that message 0xa0008000 is the *source* address (which makes sense,
> > since that is where you loaded it to). The kernel is being loaded to
> > address 0xafc00000 within dom0 RAM, which spans
> > 0xa8000000->0xb0000000.  That load address is about where I would
> > expect given the constraints (just under 128M).
> 
> I now get that Xen moves the kernel image to 0xafc00000 (PA), and DTB to
> 0xafa00000 (PA).
> 
> Few questions:
> 
>   - What does P2M stand for, and what is it?

"physical to machine". It's the Xen term for what you would call the
second stage paging.

>   - What does DOM0 see as its PC at entry?

The load address of the kernel image, since the zImage protocol requires
us to enter the kernel at that offset.

>   - Is DOM0 FDT's memory node modified at all, move base IPA or shrink
>     size etc.? Or Does DOM0 still see the RAM at 0x80000000 to
>     0xc0000000?

dom0's FDT is changed to only reflect things which dom0 has access to,
which includes adjusting the RAM to only the region which has been
allocated to dom0.

Ian.



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