Re: [PATCH 1/2 v2] x86: add max_addr boot option

H. Peter Anvin
2012-06-13T03:30:11Z

On 06/12/2012 07:21 PM, Kamezawa Hiroyuki wrote:
>
> But now, we know mem= boot option is buggy....it acts as max_addr=
> option, we have concerns that 'someone may fix mem= option as sane as ia64. because
> it's buggy".
>
> We'd like to fix mem= boot option by ourselves and preserve old behavior
> with max_addr= boot option, which ia64 has.
>

Now I'm *really* confused.

Realistically, there is no point in the old mem= behavior of assuming a
contiguous chunk of memory up to that point; it simply doesn't match how
modern hardware is constructed. Your notion that ia64 is "sane" is
probably more of "outdated" in my opinion.

As such, the current behavior for mem= seems like the right thing and
the change was intentional (not to mention has been in place since
kernel 2.5.65, back in 2003); it also solves your requirements. If you
are concerned about it, it would make more sense to make sure it is
documented as intentional.

In fact, it looks like IA64 introduced a divergence when the max_addr=
patch was introduced in 2004. You're basically proposing the same
divergence for x86 now; talk about having the tail wag the dog.

Sorry. NAK.

-hpa