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

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2014-06-11 at 16:02 +0100, Jeenu Viswambharan wrote:
> > > Xen is now launching DOM0. But next issue I'm now facing is that
> > > Linux refusing to run when loaded at 0xa0008000 - it panics and
> > > complains about failing to allocate memory in
> > > mm/memblock.c:memblock_alloc_base().  FWIW, I've built the kernel
> > > v3.14 with vexpress_defconfig and enabled Xen and highmem support.
> > > The kernel however is happy to boot when loaded at 0x80008000
> > > (without Xen). The same with Xen though, the kernel reports
> > > 'uncompression error'.
> > >
> > > It's little to do with Xen, but are there any other options required
> > > to be enabled in the DOM0 Kernel to run from 0xa0008000?
> >
> > Your kernel needs to be relocatable. I'm not 100% which option that is
> > (perhaps CONFIG_ARM_PATCH_PHYS_VIRT) but if you build a multiplatform
> > kernel (CONFIG_ARCH_MULTIPLATFORM) it certainly will be.
> 
> Just found out that both of the configs are enabled in my build, and
> I've no idea what's going on.
> 
> Like I said, when loaded at 0xa0008000, the kernel didn't boot neither
> on bare metal nor Xen. But at 0x80008000, the kernel was happy to boot
> bare metal but not with Xen. Does Xen care where the kernel is, as long
> as the kernel is happy to execute from wherever it's loaded?

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.

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).

Can you post your boot logs, perhaps they will give me a clue.

Ian.


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