Re: [PATCH 0/3] x86/pvh: Support relocating dom0 kernel

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Wed, Mar 06, 2024 at 01:50:29PM -0500, Jason Andryuk wrote:
> Xen tries to load a PVH dom0 kernel at the fixed guest physical address
> from the elf headers.  For Linux, this defaults to 0x1000000 (16MB), but
> it can be configured.
> 
> Unfortunately there exist firmwares that have reserved regions at this
> address, so Xen fails to load the dom0 kernel since it's not RAM.
> 
> The other issue is that the Linux PVH entry point is not
> position-independent.  It expects to run at the compiled
> CONFIG_PHYSICAL_ADDRESS.
> 
> This patch set expands the PVH dom0 builder to try to relocate the
> kernel if needed and possible.  XENFEAT_pvh_relocatable is added for
> kernels to indicate they are relocatable.  However, we may want to
> switch to an additional ELF note with the kernel alignment.  Linux
> specifies a kernel alignment in the bzImage boot_params.setup_header,
> but that is not present the ELF vmlinux file.

I wonder whether we need a pair of notes, to signal the min/max
addresses the kernel supports being relocated to.

Thanks, Roger.