Re: [PATCH] libxc: arm: Load the zImage to the rambase address + 2MB

[Julien Grall <julien.grall@linaro.org>]

On 07/03/2014 11:37 AM, Thomas Leonard wrote:
>> Using 4K alignment make impossible to use 1MB or 2MB mapping for early
>> page table. Which make the code (usually in assembly) even harder to
>> write or to impose relocation in the assembly code.
> 
> This isn't the case for Mini-OS, at least. We already use a 1MB mapping
> with the 0x8000 offset just fine. The translation table (using 1MB
> sections) is 16K, which would fit nicely in the 0x8000 gap (although
> currently we don't use that space).

As I said in Mini-OS series, the spec doesn't say anything about the
start offset of the guest kernel for the Linux boot protocol.

0x8000 offset is very inconvenient for most of the other OS than Linux.
As Linux is able to relocate itself, I don't see any known issue about
starting at an 2MB-aligned address.

> Starting at 2MB would create an inconvenient 2MB of free memory just
> before the kernel, with no obvious way to tell xmalloc about it.

That's a bug in Mini-OS in this case. Why can't you use the whole memory?

Regards,

-- 
Julien Grall