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

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2014-07-03 at 12:12 +0100, Julien Grall wrote:
> 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.

The known issue is that you cannot rely going forward on the address
always being 2MB aligned. You *cannot* assume this.

Ian.


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel