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Subject[PATCH] [15/36] CPA: Change kernel_map_pages to not use c_p_a()
Date

CONFIG_DEBUG_PAGEALLOC uses change_page_attr to map/unmap mappings for catching
stray kernel mappings. But standard c_p_a() does a lot of unnecessary work for
this simple case with pre-split mappings.

Change kernel_map_pages to just access the page table directly which
is simpler and faster.

I also fixed it to use INVLPG if available.

This is required for changes to c_p_a() later that make it use kmalloc. Without
this we would risk infinite recursion. Also in general things are easier when
sleeping is allowed.

Signed-off-by: Andi Kleen <ak@suse.de>
Acked-by: Jan Beulich <jbeulich@novell.com>

---
arch/x86/mm/pageattr_32.c | 34 ++++++++++++++++++++++++----------
1 file changed, 24 insertions(+), 10 deletions(-)
Index: linux/arch/x86/mm/pageattr_32.c
===================================================================
--- linux.orig/arch/x86/mm/pageattr_32.c
+++ linux/arch/x86/mm/pageattr_32.c
@@ -274,22 +274,36 @@ void global_flush_tlb(void)
}

#ifdef CONFIG_DEBUG_PAGEALLOC
+/* Map or unmap pages in the kernel direct mapping for kernel debugging. */
void kernel_map_pages(struct page *page, int numpages, int enable)
{
+ unsigned long addr;
+ int i;
+
if (PageHighMem(page))
return;
+ addr = (unsigned long)page_address(page);
if (!enable)
- debug_check_no_locks_freed(page_address(page),
- numpages * PAGE_SIZE);
+ debug_check_no_locks_freed((void *)addr, numpages * PAGE_SIZE);
+
+ /* Bootup has forced 4K pages so this is very simple */
+
+ for (i = 0; i < numpages; i++, addr += PAGE_SIZE, page++) {
+ int level;
+ pte_t *pte = lookup_address(addr, &level);

- /* the return value is ignored - the calls cannot fail,
- * large pages are disabled at boot time.
- */
- change_page_attr(page, numpages, enable ? PAGE_KERNEL : __pgprot(0));
- /* we should perform an IPI and flush all tlbs,
- * but that can deadlock->flush only current cpu.
- */
- __flush_tlb_all();
+ BUG_ON(level != 3);
+ if (enable) {
+ set_pte_atomic(pte, mk_pte(page, PAGE_KERNEL));
+ /*
+ * We should perform an IPI and flush all tlbs,
+ * but that can deadlock->flush only current cpu.
+ */
+ __flush_tlb_one(addr);
+ } else {
+ kpte_clear_flush(pte, addr);
+ }
+ }
}
#endif


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