text: // SPDX-License-Identifier: GPL-2.0-or-later
  /*
   * Copyright 2005, Paul Mackerras, IBM Corporation.
   * Copyright 2009, Benjamin Herrenschmidt, IBM Corporation.
   * Copyright 2015-2016, Aneesh Kumar K.V, IBM Corporation.
   */
  
  #include <linux/sched.h>
  #include <linux/mm_types.h>
  #include <linux/mm.h>
  
  #include <asm/pgalloc.h>
  #include <asm/pgtable.h>
  #include <asm/sections.h>
  #include <asm/mmu.h>
  #include <asm/tlb.h>
  
  #include <mm/mmu_decl.h>
  
  #define CREATE_TRACE_POINTS
  #include <trace/events/thp.h>
  
  #if H_PGTABLE_RANGE > (USER_VSID_RANGE * (TASK_SIZE_USER64 / TASK_CONTEXT_SIZE))
  #warning Limited user VSID range means pagetable space is wasted
  #endif
  
  #ifdef CONFIG_SPARSEMEM_VMEMMAP
  /*
   * vmemmap is the starting address of the virtual address space where
   * struct pages are allocated for all possible PFNs present on the system
   * including holes and bad memory (hence sparse). These virtual struct
   * pages are stored in sequence in this virtual address space irrespective
   * of the fact whether the corresponding PFN is valid or not. This achieves
   * constant relationship between address of struct page and its PFN.
   *
   * During boot or memory hotplug operation when a new memory section is
   * added, physical memory allocation (including hash table bolting) will
   * be performed for the set of struct pages which are part of the memory
   * section. This saves memory by not allocating struct pages for PFNs
   * which are not valid.
   *
   *		----------------------------------------------
   *		| PHYSICAL ALLOCATION OF VIRTUAL STRUCT PAGES|
   *		----------------------------------------------
   *
   *	   f000000000000000                  c000000000000000
   * vmemmap +--------------+                  +--------------+
   *  +      |  page struct | +--------------> |  page struct |
   *  |      +--------------+                  +--------------+
   *  |      |  page struct | +--------------> |  page struct |
   *  |      +--------------+ |                +--------------+
   *  |      |  page struct | +       +------> |  page struct |
   *  |      +--------------+         |        +--------------+
   *  |      |  page struct |         |   +--> |  page struct |
   *  |      +--------------+         |   |    +--------------+
   *  |      |  page struct |         |   |
   *  |      +--------------+         |   |
   *  |      |  page struct |         |   |
   *  |      +--------------+         |   |
   *  |      |  page struct |         |   |
   *  |      +--------------+         |   |
   *  |      |  page struct |         |   |
   *  |      +--------------+         |   |
   *  |      |  page struct | +-------+   |
   *  |      +--------------+             |
   *  |      |  page struct | +-----------+
   *  |      +--------------+
   *  |      |  page struct | No mapping
   *  |      +--------------+
   *  |      |  page struct | No mapping
   *  v      +--------------+
   *
   *		-----------------------------------------
   *		| RELATION BETWEEN STRUCT PAGES AND PFNS|
   *		-----------------------------------------
   *
   * vmemmap +--------------+                 +---------------+
   *  +      |  page struct | +-------------> |      PFN      |
   *  |      +--------------+                 +---------------+
   *  |      |  page struct | +-------------> |      PFN      |
   *  |      +--------------+                 +---------------+
   *  |      |  page struct | +-------------> |      PFN      |
   *  |      +--------------+                 +---------------+
   *  |      |  page struct | +-------------> |      PFN      |
   *  |      +--------------+                 +---------------+
   *  |      |              |
   *  |      +--------------+
   *  |      |              |
   *  |      +--------------+
   *  |      |              |
   *  |      +--------------+                 +---------------+
   *  |      |  page struct | +-------------> |      PFN      |
   *  |      +--------------+                 +---------------+
   *  |      |              |
   *  |      +--------------+
   *  |      |              |
   *  |      +--------------+                 +---------------+
   *  |      |  page struct | +-------------> |      PFN      |
   *  |      +--------------+                 +---------------+
   *  |      |  page struct | +-------------> |      PFN      |
   *  v      +--------------+                 +---------------+
   */
  /*
   * On hash-based CPUs, the vmemmap is bolted in the hash table.
   *
   */
  int __meminit hash__vmemmap_create_mapping(unsigned long start,
  				       unsigned long page_size,
  				       unsigned long phys)
  {
  	int rc;
  
  	if ((start + page_size) >= H_VMEMMAP_END) {
  		pr_warn("Outside the supported range\n");
  		return -1;
  	}
  
  	rc = htab_bolt_mapping(start, start + page_size, phys,
  			       pgprot_val(PAGE_KERNEL),
  			       mmu_vmemmap_psize, mmu_kernel_ssize);
  	if (rc < 0) {
  		int rc2 = htab_remove_mapping(start, start + page_size,
  					      mmu_vmemmap_psize,
  					      mmu_kernel_ssize);
  		BUG_ON(rc2 && (rc2 != -ENOENT));
  	}
  	return rc;
  }
  
  #ifdef CONFIG_MEMORY_HOTPLUG
  void hash__vmemmap_remove_mapping(unsigned long start,
  			      unsigned long page_size)
  {
  	int rc = htab_remove_mapping(start, start + page_size,
  				     mmu_vmemmap_psize,
  				     mmu_kernel_ssize);
  	BUG_ON((rc < 0) && (rc != -ENOENT));
  	WARN_ON(rc == -ENOENT);
  }
  #endif
  #endif /* CONFIG_SPARSEMEM_VMEMMAP */
  
  /*
   * map_kernel_page currently only called by __ioremap
   * map_kernel_page adds an entry to the ioremap page table
   * and adds an entry to the HPT, possibly bolting it
   */
  int hash__map_kernel_page(unsigned long ea, unsigned long pa, pgprot_t prot)
  {
  	pgd_t *pgdp;
  	pud_t *pudp;
  	pmd_t *pmdp;
  	pte_t *ptep;
  
  	BUILD_BUG_ON(TASK_SIZE_USER64 > H_PGTABLE_RANGE);
  	if (slab_is_available()) {
  		pgdp = pgd_offset_k(ea);
  		pudp = pud_alloc(&init_mm, pgdp, ea);
  		if (!pudp)
  			return -ENOMEM;
  		pmdp = pmd_alloc(&init_mm, pudp, ea);
  		if (!pmdp)
  			return -ENOMEM;
  		ptep = pte_alloc_kernel(pmdp, ea);
  		if (!ptep)
  			return -ENOMEM;
  		set_pte_at(&init_mm, ea, ptep, pfn_pte(pa >> PAGE_SHIFT, prot));
  	} else {
  		/*
  		 * If the mm subsystem is not fully up, we cannot create a
  		 * linux page table entry for this mapping.  Simply bolt an
  		 * entry in the hardware page table.
  		 *
  		 */
  		if (htab_bolt_mapping(ea, ea + PAGE_SIZE, pa, pgprot_val(prot),
  				      mmu_io_psize, mmu_kernel_ssize)) {
  			printk(KERN_ERR "Failed to do bolted mapping IO "
  			       "memory at %016lx !\n", pa);
  			return -ENOMEM;
  		}
  	}
  
  	smp_wmb();
  	return 0;
  }
  
  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
  
  unsigned long hash__pmd_hugepage_update(struct mm_struct *mm, unsigned long addr,
  				    pmd_t *pmdp, unsigned long clr,
  				    unsigned long set)
  {
  	__be64 old_be, tmp;
  	unsigned long old;
  
  #ifdef CONFIG_DEBUG_VM
  	WARN_ON(!hash__pmd_trans_huge(*pmdp) && !pmd_devmap(*pmdp));
  	assert_spin_locked(pmd_lockptr(mm, pmdp));
  #endif
  
  	__asm__ __volatile__(
  	"1:	ldarx	%0,0,%3\n\
  		and.	%1,%0,%6\n\
  		bne-	1b \n\
  		andc	%1,%0,%4 \n\
  		or	%1,%1,%7\n\
  		stdcx.	%1,0,%3 \n\
  		bne-	1b"
  	: "=&r" (old_be), "=&r" (tmp), "=m" (*pmdp)
  	: "r" (pmdp), "r" (cpu_to_be64(clr)), "m" (*pmdp),
  	  "r" (cpu_to_be64(H_PAGE_BUSY)), "r" (cpu_to_be64(set))
  	: "cc" );
  
  	old = be64_to_cpu(old_be);
  
  	trace_hugepage_update(addr, old, clr, set);
  	if (old & H_PAGE_HASHPTE)
  		hpte_do_hugepage_flush(mm, addr, pmdp, old);
  	return old;
  }
  
  pmd_t hash__pmdp_collapse_flush(struct vm_area_struct *vma, unsigned long address,
  			    pmd_t *pmdp)
  {
  	pmd_t pmd;
  
  	VM_BUG_ON(address & ~HPAGE_PMD_MASK);
  	VM_BUG_ON(pmd_trans_huge(*pmdp));
  	VM_BUG_ON(pmd_devmap(*pmdp));
  
  	pmd = *pmdp;
  	pmd_clear(pmdp);
  	/*
  	 * Wait for all pending hash_page to finish. This is needed
  	 * in case of subpage collapse. When we collapse normal pages
  	 * to hugepage, we first clear the pmd, then invalidate all
  	 * the PTE entries. The assumption here is that any low level
  	 * page fault will see a none pmd and take the slow path that
  	 * will wait on mmap_sem. But we could very well be in a
  	 * hash_page with local ptep pointer value. Such a hash page
  	 * can result in adding new HPTE entries for normal subpages.
  	 * That means we could be modifying the page content as we
  	 * copy them to a huge page. So wait for parallel hash_page
  	 * to finish before invalidating HPTE entries. We can do this
  	 * by sending an IPI to all the cpus and executing a dummy
  	 * function there.
  	 */
  	serialize_against_pte_lookup(vma->vm_mm);
  	/*
  	 * Now invalidate the hpte entries in the range
  	 * covered by pmd. This make sure we take a
  	 * fault and will find the pmd as none, which will
  	 * result in a major fault which takes mmap_sem and
  	 * hence wait for collapse to complete. Without this
  	 * the __collapse_huge_page_copy can result in copying
  	 * the old content.
  	 */
  	flush_tlb_pmd_range(vma->vm_mm, &pmd, address);
  	return pmd;
  }
  
  /*
   * We want to put the pgtable in pmd and use pgtable for tracking
   * the base page size hptes
   */
  void hash__pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,
  				  pgtable_t pgtable)
  {
  	pgtable_t *pgtable_slot;
  
  	assert_spin_locked(pmd_lockptr(mm, pmdp));
  	/*
  	 * we store the pgtable in the second half of PMD
  	 */
  	pgtable_slot = (pgtable_t *)pmdp + PTRS_PER_PMD;
  	*pgtable_slot = pgtable;
  	/*
  	 * expose the deposited pgtable to other cpus.
  	 * before we set the hugepage PTE at pmd level
  	 * hash fault code looks at the deposted pgtable
  	 * to store hash index values.
  	 */
  	smp_wmb();
  }
  
  pgtable_t hash__pgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t *pmdp)
  {
  	pgtable_t pgtable;
  	pgtable_t *pgtable_slot;
  
  	assert_spin_locked(pmd_lockptr(mm, pmdp));
  
  	pgtable_slot = (pgtable_t *)pmdp + PTRS_PER_PMD;
  	pgtable = *pgtable_slot;
  	/*
  	 * Once we withdraw, mark the entry NULL.
  	 */
  	*pgtable_slot = NULL;
  	/*
  	 * We store HPTE information in the deposited PTE fragment.
  	 * zero out the content on withdraw.
  	 */
  	memset(pgtable, 0, PTE_FRAG_SIZE);
  	return pgtable;
  }
  
  /*
   * A linux hugepage PMD was changed and the corresponding hash table entries
   * neesd to be flushed.
   */
  void hpte_do_hugepage_flush(struct mm_struct *mm, unsigned long addr,
  			    pmd_t *pmdp, unsigned long old_pmd)
  {
  	int ssize;
  	unsigned int psize;
  	unsigned long vsid;
  	unsigned long flags = 0;
  
  	/* get the base page size,vsid and segment size */
  #ifdef CONFIG_DEBUG_VM
  	psize = get_slice_psize(mm, addr);
  	BUG_ON(psize == MMU_PAGE_16M);
  #endif
  	if (old_pmd & H_PAGE_COMBO)
  		psize = MMU_PAGE_4K;
  	else
  		psize = MMU_PAGE_64K;
  
  	if (!is_kernel_addr(addr)) {
  		ssize = user_segment_size(addr);
  		vsid = get_user_vsid(&mm->context, addr, ssize);
  		WARN_ON(vsid == 0);
  	} else {
  		vsid = get_kernel_vsid(addr, mmu_kernel_ssize);
  		ssize = mmu_kernel_ssize;
  	}
  
  	if (mm_is_thread_local(mm))
  		flags |= HPTE_LOCAL_UPDATE;
  
  	return flush_hash_hugepage(vsid, addr, pmdp, psize, ssize, flags);
  }
  
  pmd_t hash__pmdp_huge_get_and_clear(struct mm_struct *mm,
  				unsigned long addr, pmd_t *pmdp)
  {
  	pmd_t old_pmd;
  	pgtable_t pgtable;
  	unsigned long old;
  	pgtable_t *pgtable_slot;
  
  	old = pmd_hugepage_update(mm, addr, pmdp, ~0UL, 0);
  	old_pmd = __pmd(old);
  	/*
  	 * We have pmd == none and we are holding page_table_lock.
  	 * So we can safely go and clear the pgtable hash
  	 * index info.
  	 */
  	pgtable_slot = (pgtable_t *)pmdp + PTRS_PER_PMD;
  	pgtable = *pgtable_slot;
  	/*
  	 * Let's zero out old valid and hash index details
  	 * hash fault look at them.
  	 */
  	memset(pgtable, 0, PTE_FRAG_SIZE);
  	/*
  	 * Serialize against find_current_mm_pte variants which does lock-less
  	 * lookup in page tables with local interrupts disabled. For huge pages
  	 * it casts pmd_t to pte_t. Since format of pte_t is different from
  	 * pmd_t we want to prevent transit from pmd pointing to page table
  	 * to pmd pointing to huge page (and back) while interrupts are disabled.
  	 * We clear pmd to possibly replace it with page table pointer in
  	 * different code paths. So make sure we wait for the parallel
  	 * find_curren_mm_pte to finish.
  	 */
  	serialize_against_pte_lookup(mm);
  	return old_pmd;
  }
  
  int hash__has_transparent_hugepage(void)
  {
  
  	if (!mmu_has_feature(MMU_FTR_16M_PAGE))
  		return 0;
  	/*
  	 * We support THP only if PMD_SIZE is 16MB.
  	 */
  	if (mmu_psize_defs[MMU_PAGE_16M].shift != PMD_SHIFT)
  		return 0;
  	/*
  	 * We need to make sure that we support 16MB hugepage in a segement
  	 * with base page size 64K or 4K. We only enable THP with a PAGE_SIZE
  	 * of 64K.
  	 */
  	/*
  	 * If we have 64K HPTE, we will be using that by default
  	 */
  	if (mmu_psize_defs[MMU_PAGE_64K].shift &&
  	    (mmu_psize_defs[MMU_PAGE_64K].penc[MMU_PAGE_16M] == -1))
  		return 0;
  	/*
  	 * Ok we only have 4K HPTE
  	 */
  	if (mmu_psize_defs[MMU_PAGE_4K].penc[MMU_PAGE_16M] == -1)
  		return 0;
  
  	return 1;
  }
  #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
  
  #ifdef CONFIG_STRICT_KERNEL_RWX
  static bool hash__change_memory_range(unsigned long start, unsigned long end,
  				      unsigned long newpp)
  {
  	unsigned long idx;
  	unsigned int step, shift;
  
  	shift = mmu_psize_defs[mmu_linear_psize].shift;
  	step = 1 << shift;
  
  	start = ALIGN_DOWN(start, step);
  	end = ALIGN(end, step); // aligns up
  
  	if (start >= end)
  		return false;
  
  	pr_debug("Changing page protection on range 0x%lx-0x%lx, to 0x%lx, step 0x%x\n",
  		 start, end, newpp, step);
  
  	for (idx = start; idx < end; idx += step)
  		/* Not sure if we can do much with the return value */
  		mmu_hash_ops.hpte_updateboltedpp(newpp, idx, mmu_linear_psize,
  							mmu_kernel_ssize);
  
  	return true;
  }
  
  void hash__mark_rodata_ro(void)
  {
  	unsigned long start, end;
  
  	start = (unsigned long)_stext;
  	end = (unsigned long)__init_begin;
  
  	WARN_ON(!hash__change_memory_range(start, end, PP_RXXX));
  }
  
  void hash__mark_initmem_nx(void)
  {
  	unsigned long start, end, pp;
  
  	start = (unsigned long)__init_begin;
  	end = (unsigned long)__init_end;
  
  	pp = htab_convert_pte_flags(pgprot_val(PAGE_KERNEL));
  
  	WARN_ON(!hash__change_memory_range(start, end, pp));
  }
  #endif
  