mirrors
/
linux-stable
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
1
0
Fork 0
Code Issues Releases Wiki Activity

Merge branch 'x86-mm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull x86 mm fixlet from Ingo Molnar:
 "One cleanup that documents a particular detail in init_mem_mapping()"

* 'x86-mm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/mm: Add 'step_size' comments to init_mem_mapping()
This commit is contained in:
Linus Torvalds 2013-11-12 11:20:52 +09:00
parent 340286cd4e 6979287a7d
commit 2612c49db3
1 changed files with 20 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

23
arch/x86/mm/init.c
View File

@ -399,8 +399,25 @@ static unsigned long __init init_range_memory_mapping(
return mapped_ram_size;
}
/* (PUD_SHIFT-PMD_SHIFT)/2 */
#define STEP_SIZE_SHIFT 5
static unsigned long __init get_new_step_size(unsigned long step_size)
{
/*
* Explain why we shift by 5 and why we don't have to worry about
* 'step_size << 5' overflowing:
*
* initial mapped size is PMD_SIZE (2M).
* We can not set step_size to be PUD_SIZE (1G) yet.
* In worse case, when we cross the 1G boundary, and
* PG_LEVEL_2M is not set, we will need 1+1+512 pages (2M + 8k)
* to map 1G range with PTE. Use 5 as shift for now.
*
* Don't need to worry about overflow, on 32bit, when step_size
* is 0, round_down() returns 0 for start, and that turns it
* into 0x100000000ULL.
*/
return step_size << 5;
}
void __init init_mem_mapping(void)
{
unsigned long end, real_end, start, last_start;
@ -449,7 +466,7 @@ void __init init_mem_mapping(void)
min_pfn_mapped = last_start >> PAGE_SHIFT;
/* only increase step_size after big range get mapped */
if (new_mapped_ram_size > mapped_ram_size)
step_size <<= STEP_SIZE_SHIFT;
step_size = get_new_step_size(step_size);
mapped_ram_size += new_mapped_ram_size;
}