Re: [PATCH] [RESEND] arm: limit memblock base address for early_pte_alloc

Nicolas Pitre
2012-06-28T17:50:22Z

On Thu, 28 Jun 2012, Russell King - ARM Linux wrote:

> Err, I don't think you understand what's going on here.
>
> The sequence is:
>
> 1. setup the initial mappings so we can run the kernel in virtual space.
> 2. provide the memory areas to memblock
> 3. ask the platform to reserve whatever memory it wants from memblock
> [this means using memblock_reserve or arm_memblock_steal). The
> reserved memory is *not* expected to be mapped at this point, and is
> therefore inaccessible.
> 4. Setup the lowmem mappings.

I do understand that pretty well so far.

> And when we're setting up the lowmem mappings, we do *not* expect to
> create any non-section page mappings, which again means we have no reason
> to use the memblock allocator to obtain memory that we want to immediately
> use.

And why does this have to remain so?

> So I don't know where you're claim of being "fragile" is coming from.

It doesn't come from anything you've described so far. It comes from
those previous attempts at lifting this limitation. I think that my
proposal is much less fragile than the other ones.

> What is fragile is people wanting to use arm_memblock_steal() without
> following the rules for it I layed down.

What about enhancing your rules if the technical limitations they were
based on are lifted?

Nicolas