Use of __pa() with CONFIG_NONLINEAR

Dave Hansen
2004-07-27T22:00:48Z

So, for CONFIG_NONLINEAR, we introduce a new indirection layer for
virtual to physical conversions (and the inverse as well). Our
implementation uses some data structures to do this (patch is here:
http://lwn.net/Articles/79124/), and the side-effect is that we can't
use __pa() or __va() until after the initialization has run, which is
early in setup_arch().

But, there are quite a few things that obviously need physical addresses
earlier than that, such as cr3 initialization at compile-time. So, in
Dave McCracken's patch, he introduced a new function: __boot_pa() that
does what the old __pa() did.

This is the largest and hardest to maintain part of the CONFIG_NONLINEAR
patch at this point, and I'd love to start merging bits of it back in.
Would anybody object to a patch that just does this for a bunch of
architectures?

--- include/asm-i386/page.h.orig 2004-07-27 14:31:09.000000000 -0700
+++ include/asm-i386/page.h 2004-07-27 14:31:36.000000000 -0700
@@ -128,8 +128,10 @@ static __inline__ int get_order(unsigned
#define PAGE_OFFSET ((unsigned long)__PAGE_OFFSET)
#define VMALLOC_RESERVE ((unsigned long)__VMALLOC_RESERVE)
#define MAXMEM (-__PAGE_OFFSET-__VMALLOC_RESERVE)
-#define __pa(x) ((unsigned long)(x)-PAGE_OFFSET)
-#define __va(x) ((void *)((unsigned long)(x)+PAGE_OFFSET))
+#define __boot_pa(x) ((unsigned long)(x)-PAGE_OFFSET)
+#define __boot_va(x) ((void *)((unsigned long)(x)+PAGE_OFFSET))
+#define __pa(x) __boot_pa(x)
+#define __va(x) __boot_va(x)
#define pfn_to_kaddr(pfn) __va((pfn) << PAGE_SHIFT)
#ifndef CONFIG_DISCONTIGMEM
#define pfn_to_page(pfn) (mem_map + (pfn))

We will, of course be overriding __{v,p}a() for any architectures that
we do nonlinear with, later on.

The only other thing I can think of is to make __pa() effectively the
boot-time, simple one, and make virt_to_phys() the more sophisticated
one that we override with nonlinear. But, some architectures '#define
__pa() virt_to_phys()', while others do the opposite, so that approach
could be significantly more work.

Does anybody really remember what the different between the __{p,v}a()
functions and the virt_to_phys() ones is supposed to be?

-- Dave