Revert "xen/mmu: Add workaround "x86-64, mm: Put early page table high""

	return ret;

}

#ifdef CONFIG_X86_64

static __initdata u64 __last_pgt_set_rw = 0;

static __initdata u64 __pgt_buf_start = 0;

static __initdata u64 __pgt_buf_end = 0;

static __initdata u64 __pgt_buf_top = 0;

/*

 * As a consequence of the commit:

 * 

 * commit 4b239f458c229de044d6905c2b0f9fe16ed9e01e

 * Author: Yinghai Lu <yinghai@kernel.org>

 * Date:   Fri Dec 17 16:58:28 2010 -0800

 * 

 *     x86-64, mm: Put early page table high

 * 

 * at some point init_memory_mapping is going to reach the pagetable pages

 * area and map those pages too (mapping them as normal memory that falls

 * in the range of addresses passed to init_memory_mapping as argument).

 * Some of those pages are already pagetable pages (they are in the range

 * pgt_buf_start-pgt_buf_end) therefore they are going to be mapped RO and

 * everything is fine.

 * Some of these pages are not pagetable pages yet (they fall in the range

 * pgt_buf_end-pgt_buf_top; for example the page at pgt_buf_end) so they

 * are going to be mapped RW.  When these pages become pagetable pages and

 * are hooked into the pagetable, xen will find that the guest has already

 * a RW mapping of them somewhere and fail the operation.

 * The reason Xen requires pagetables to be RO is that the hypervisor needs

 * to verify that the pagetables are valid before using them. The validation

 * operations are called "pinning".

 * 

 * In order to fix the issue we mark all the pages in the entire range

 * pgt_buf_start-pgt_buf_top as RO, however when the pagetable allocation

 * is completed only the range pgt_buf_start-pgt_buf_end is reserved by

 * init_memory_mapping. Hence the kernel is going to crash as soon as one

 * of the pages in the range pgt_buf_end-pgt_buf_top is reused (b/c those

 * ranges are RO).

 * 

 * For this reason, 'mark_rw_past_pgt' is introduced which is called _after_

 * the init_memory_mapping has completed (in a perfect world we would

 * call this function from init_memory_mapping, but lets ignore that).

 * 

 * Because we are called _after_ init_memory_mapping the pgt_buf_[start,

 * end,top] have all changed to new values (b/c init_memory_mapping

 * is called and setting up another new page-table). Hence, the first time

 * we enter this function, we save away the pgt_buf_start value and update

 * the pgt_buf_[end,top].

 * 

 * When we detect that the "old" pgt_buf_start through pgt_buf_end

 * PFNs have been reserved (so memblock_x86_reserve_range has been called),

 * we immediately set out to RW the "old" pgt_buf_end through pgt_buf_top.

 * 

 * And then we update those "old" pgt_buf_[end|top] with the new ones

 * so that we can redo this on the next pagetable.

 */

static __init void mark_rw_past_pgt(void) {

	if (pgt_buf_end > pgt_buf_start) {

		u64 addr, size;

		/* Save it away. */

		if (!__pgt_buf_start) {

			__pgt_buf_start = pgt_buf_start;

			__pgt_buf_end = pgt_buf_end;

			__pgt_buf_top = pgt_buf_top;

			return;

		}

		/* If we get the range that starts at __pgt_buf_end that means

		 * the range is reserved, and that in 'init_memory_mapping'

		 * the 'memblock_x86_reserve_range' has been called with the

		 * outdated __pgt_buf_start, __pgt_buf_end (the "new"

		 * pgt_buf_[start|end|top] refer now to a new pagetable.

		 * Note: we are called _after_ the pgt_buf_[..] have been

		 * updated.*/

		addr = memblock_x86_find_in_range_size(PFN_PHYS(__pgt_buf_start),

						       &size, PAGE_SIZE);

		/* Still not reserved, meaning 'memblock_x86_reserve_range'

		 * hasn't been called yet. Update the _end and _top.*/

		if (addr == PFN_PHYS(__pgt_buf_start)) {

			__pgt_buf_end = pgt_buf_end;

			__pgt_buf_top = pgt_buf_top;

			return;

		}

		/* OK, the area is reserved, meaning it is time for us to

		 * set RW for the old end->top PFNs. */

		/* ..unless we had already done this. */

		if (__pgt_buf_end == __last_pgt_set_rw)

			return;

		addr = PFN_PHYS(__pgt_buf_end);

		/* set as RW the rest */

		printk(KERN_DEBUG "xen: setting RW the range %llx - %llx\n",

			PFN_PHYS(__pgt_buf_end), PFN_PHYS(__pgt_buf_top));

		while (addr < PFN_PHYS(__pgt_buf_top)) {

			make_lowmem_page_readwrite(__va(addr));

			addr += PAGE_SIZE;

		}

		/* And update everything so that we are ready for the next

		 * pagetable (the one created for regions past 4GB) */

		__last_pgt_set_rw = __pgt_buf_end;

		__pgt_buf_start = pgt_buf_start;

		__pgt_buf_end = pgt_buf_end;

		__pgt_buf_top = pgt_buf_top;

	}

	return;

}

#else

static __init void mark_rw_past_pgt(void) { }

#endif

static void xen_pgd_free(struct mm_struct *mm, pgd_t *pgd)

{

#ifdef CONFIG_X86_64

{

	unsigned long pfn = pte_pfn(pte);

	/*

	 * A bit of optimization. We do not need to call the workaround

	 * when xen_set_pte_init is called with a PTE with 0 as PFN.

	 * That is b/c the pagetable at that point are just being populated

	 * with empty values and we can save some cycles by not calling

	 * the 'memblock' code.*/

	if (pfn)

		mark_rw_past_pgt();

	/*

	 * If the new pfn is within the range of the newly allocated

	 * kernel pagetable, and it isn't being mapped into an

static __init void xen_post_allocator_init(void)

{

	mark_rw_past_pgt();

#ifdef CONFIG_XEN_DEBUG

	pv_mmu_ops.make_pte = PV_CALLEE_SAVE(xen_make_pte_debug);

#endif