Re: [PATCH v4 1/3] x86: Introduce a new constant KERNEL_MAPPING_SIZE

[Baoquan He <bhe@redhat.com>]

On 03/03/17 at 12:43pm, Borislav Petkov wrote:
> On Sun, Feb 26, 2017 at 12:09:08PM +0800, Baoquan He wrote:
> > Am I right on understanding it?
> 
> That's exactly what I mean: KERNEL_IMAGE_SIZE is 512M by default but
> we're not hard-constrained to it - we're hard-constrained to a 1G limit
> as this is the 1G which is covered by level2_kernel_pgt.
> 
> And in thinking about this more, I know I suggested making the
> KERNEL_IMAGE_SIZE by default 1G in order to simplify things.
> 
> But you're adding another KERNEL_MAPPING_SIZE which confuses things
> more. And I fail to see why we absolutely need it.

OK, I am trying to make things clearer, seems I failed. I thought kernel
iamge size is only allowed to be 512M at most, but can be mapped into 1G
region.
> 
> So we suggest kernel image size should be 512M but then we still will
> be using a whole 1G mapping for it anyway and a whole page of PMDs at
> level2_kernel_pgt.
> 
> So why even bother?
> 
> Just make it 1G and don't introduce anything new.

It's fine to me, thing can be solved anyway. Will repost with
KERNEL_IMAGE_SIZE by default 1G.

Thanks
Baoquan