Re: [Patch v4 09/12] memory-hotplug: remove page table of x86_64 architecture

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On 11/27/2012 06:00 PM, Wen Congyang wrote:
For hot removing memory, we sholud remove page table about the memory.
So the patch searches a page table about the removed memory, and clear
page table.

(snip)

+void __meminit
+kernel_physical_mapping_remove(unsigned long start, unsigned long end)
+{
+	unsigned long next;
+	bool pgd_changed = false;
+
+	start = (unsigned long)__va(start);
+	end = (unsigned long)__va(end);

Hi Wu,

Here, you expect start and end are physical addresses. But in
phys_xxx_remove() function, I think using virtual addresses is just
fine. Functions like pmd_addr_end() and pud_index() only calculate
an offset.

So, would you please tell me if we have to use physical addresses here ?

Thanks. :)

+
+	for (; start<  end; start = next) {
+		pgd_t *pgd = pgd_offset_k(start);
+		pud_t *pud;
+
+		next = pgd_addr_end(start, end);
+
+		if (!pgd_present(*pgd))
+			continue;
+
+		pud = map_low_page((pud_t *)pgd_page_vaddr(*pgd));
+		phys_pud_remove(pud, __pa(start), __pa(next));
+		if (free_pud_table(pud, pgd))
+			pgd_changed = true;
+		unmap_low_page(pud);
+	}
+
+	if (pgd_changed)
+		sync_global_pgds(start, end - 1);
+
+	flush_tlb_all();
+}
+
  #ifdef CONFIG_MEMORY_HOTREMOVE
  int __ref arch_remove_memory(u64 start, u64 size)
  {
@@ -692,6 +921,8 @@ int __ref arch_remove_memory(u64 start, u64 size)
  	ret = __remove_pages(zone, start_pfn, nr_pages);
  	WARN_ON_ONCE(ret);

+	kernel_physical_mapping_remove(start, start + size);
+
  	return ret;
  }
  #endif


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