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

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2014-06-11 at 17:12 +0100, Jeenu Viswambharan wrote:

> > The kernel wants to be loaded within 128M of the start of RAM. Does
> > 0xa0008000 meet that? What is loading the kernel there -- I don't
> > think Xen will (it knows about the 128MB thing). How much RAM does
> > your vexpress have? Is 0xa0008000 even in RAM on a vexpress? I thought
> > it had up to 1GB at 0x60000000-0xa0000000.
> 
> The TC2 has 1GB RAM from 0x80000000 to 0xc0000000.

Ah, I think I was looking at the older one.

>  The instructions on
> the Wiki tells u-boot to load it at 0xa0008000 and modifies the DTB
> accordingly.

Right, so this is the host load address which I was talking about
before. This doesn't have any relationship to the address where Xen will
place the kernel in the dom0 address space.

> > And just to be clear we are talking about the load address of the
> > kernel within the dom0 IPA space, aren't we? Not the host address
> > where the kernel is loaded to be passed to Xen (it doesn't matter what
> > that is really).
> 
> I think, upon guest entry, the PC will be at 0xa0008000, making both IPA
> and PA same [1]. Is that what you were asking?

On guest entry the PC will be at the start of the kernel image, at
whatever address Xen has loaded it. Xen will load the dom0 kernel near
the start of dom0's RAM. Xen allocates dom0 RAM using a 1:1 mapping.
Perhaps Xen has allocated addresses starting at 0xa0000000 to dom0?
(that seems unlikely if you have loaded the kenrel module to pass to Xen
to that address though, since they would then clash)

> > Can you post your boot logs, perhaps they will give me a clue.
> 
> I only have
> 
>   (XEN) DOM0: Uncompressing Linux... done, booting the kernel.

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.

Ian.


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