x86: fix pte allocation in "x86: introduce init_memory_mapping for 32bit"

The patch "x86: introduce init_memory_mapping for 32bit" does not allocate enough space for PTEs if the CPU does not implement PSE.

---
arch/x86/mm/init_32.c | 5 +++++

1 file changed, 5 insertions(+)

===================================================================

@@ -733,6 +733,11 @@

	pmds = (end + PMD_SIZE - 1) >> PMD_SHIFT;
	tables += PAGE_ALIGN(pmds * sizeof(pmd_t));

+ if (!cpu_has_pse) {
+ int ptes = (end + PAGE_SIZE - 1) >> PAGE_SHIFT;
+ tables += PAGE_ALIGN(ptes * sizeof(pte_t));
+ }
+
/*
* RED-PEN putting page tables only on node 0 could
* cause a hotspot and fill up ZONE_DMA. The page tables

This code looks just like the 64-bit code (I guess it's becoming prime for unification), and I'd just spent some time debugging a bug in Xen64 caused by an overrun of the allocated area when creating non-PSE mappings of physical memory. I didn't observe a specific problem with this code, but consistency and pattern matching made it seem like a necessary addition. It only ends up reserving the amount of space actually used, so there's no wasted memory.

If you use PSE to create the mapping and have enough mapped pages anyway (small kernel), then you may not end up using any of this space.

J

applied to tip/x86/unify-setup - thanks Jeremy!

Ingo