299 lines
8.8 KiB
C
299 lines
8.8 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _ASM_X86_PGTABLE_3LEVEL_H
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#define _ASM_X86_PGTABLE_3LEVEL_H
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/*
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* Intel Physical Address Extension (PAE) Mode - three-level page
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* tables on PPro+ CPUs.
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*
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* Copyright (C) 1999 Ingo Molnar <mingo@redhat.com>
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*/
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#define pte_ERROR(e) \
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pr_err("%s:%d: bad pte %p(%08lx%08lx)\n", \
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__FILE__, __LINE__, &(e), (e).pte_high, (e).pte_low)
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#define pmd_ERROR(e) \
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pr_err("%s:%d: bad pmd %p(%016Lx)\n", \
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__FILE__, __LINE__, &(e), pmd_val(e))
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#define pgd_ERROR(e) \
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pr_err("%s:%d: bad pgd %p(%016Lx)\n", \
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__FILE__, __LINE__, &(e), pgd_val(e))
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/* Rules for using set_pte: the pte being assigned *must* be
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* either not present or in a state where the hardware will
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* not attempt to update the pte. In places where this is
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* not possible, use pte_get_and_clear to obtain the old pte
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* value and then use set_pte to update it. -ben
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*/
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static inline void native_set_pte(pte_t *ptep, pte_t pte)
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{
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ptep->pte_high = pte.pte_high;
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smp_wmb();
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ptep->pte_low = pte.pte_low;
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}
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#define pmd_read_atomic pmd_read_atomic
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/*
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* pte_offset_map_lock on 32bit PAE kernels was reading the pmd_t with
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* a "*pmdp" dereference done by gcc. Problem is, in certain places
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* where pte_offset_map_lock is called, concurrent page faults are
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* allowed, if the mmap_sem is hold for reading. An example is mincore
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* vs page faults vs MADV_DONTNEED. On the page fault side
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* pmd_populate rightfully does a set_64bit, but if we're reading the
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* pmd_t with a "*pmdp" on the mincore side, a SMP race can happen
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* because gcc will not read the 64bit of the pmd atomically. To fix
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* this all places running pmd_offset_map_lock() while holding the
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* mmap_sem in read mode, shall read the pmdp pointer using this
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* function to know if the pmd is null nor not, and in turn to know if
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* they can run pmd_offset_map_lock or pmd_trans_huge or other pmd
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* operations.
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*
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* Without THP if the mmap_sem is hold for reading, the pmd can only
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* transition from null to not null while pmd_read_atomic runs. So
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* we can always return atomic pmd values with this function.
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*
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* With THP if the mmap_sem is hold for reading, the pmd can become
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* trans_huge or none or point to a pte (and in turn become "stable")
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* at any time under pmd_read_atomic. We could read it really
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* atomically here with a atomic64_read for the THP enabled case (and
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* it would be a whole lot simpler), but to avoid using cmpxchg8b we
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* only return an atomic pmdval if the low part of the pmdval is later
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* found stable (i.e. pointing to a pte). And we're returning a none
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* pmdval if the low part of the pmd is none. In some cases the high
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* and low part of the pmdval returned may not be consistent if THP is
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* enabled (the low part may point to previously mapped hugepage,
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* while the high part may point to a more recently mapped hugepage),
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* but pmd_none_or_trans_huge_or_clear_bad() only needs the low part
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* of the pmd to be read atomically to decide if the pmd is unstable
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* or not, with the only exception of when the low part of the pmd is
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* zero in which case we return a none pmd.
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*/
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static inline pmd_t pmd_read_atomic(pmd_t *pmdp)
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{
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pmdval_t ret;
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u32 *tmp = (u32 *)pmdp;
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ret = (pmdval_t) (*tmp);
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if (ret) {
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/*
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* If the low part is null, we must not read the high part
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* or we can end up with a partial pmd.
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*/
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smp_rmb();
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ret |= ((pmdval_t)*(tmp + 1)) << 32;
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}
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return (pmd_t) { ret };
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}
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static inline void native_set_pte_atomic(pte_t *ptep, pte_t pte)
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{
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set_64bit((unsigned long long *)(ptep), native_pte_val(pte));
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}
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static inline void native_set_pmd(pmd_t *pmdp, pmd_t pmd)
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{
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set_64bit((unsigned long long *)(pmdp), native_pmd_val(pmd));
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}
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static inline void native_set_pud(pud_t *pudp, pud_t pud)
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{
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set_64bit((unsigned long long *)(pudp), native_pud_val(pud));
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}
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/*
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* For PTEs and PDEs, we must clear the P-bit first when clearing a page table
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* entry, so clear the bottom half first and enforce ordering with a compiler
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* barrier.
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*/
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static inline void native_pte_clear(struct mm_struct *mm, unsigned long addr,
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pte_t *ptep)
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{
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ptep->pte_low = 0;
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smp_wmb();
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ptep->pte_high = 0;
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}
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static inline void native_pmd_clear(pmd_t *pmd)
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{
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u32 *tmp = (u32 *)pmd;
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*tmp = 0;
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smp_wmb();
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*(tmp + 1) = 0;
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}
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static inline void native_pud_clear(pud_t *pudp)
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{
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}
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static inline void pud_clear(pud_t *pudp)
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{
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set_pud(pudp, __pud(0));
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/*
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* According to Intel App note "TLBs, Paging-Structure Caches,
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* and Their Invalidation", April 2007, document 317080-001,
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* section 8.1: in PAE mode we explicitly have to flush the
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* TLB via cr3 if the top-level pgd is changed...
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*
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* Currently all places where pud_clear() is called either have
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* flush_tlb_mm() followed or don't need TLB flush (x86_64 code or
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* pud_clear_bad()), so we don't need TLB flush here.
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*/
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}
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#ifdef CONFIG_SMP
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static inline pte_t native_ptep_get_and_clear(pte_t *ptep)
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{
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pte_t res;
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/* xchg acts as a barrier before the setting of the high bits */
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res.pte_low = xchg(&ptep->pte_low, 0);
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res.pte_high = ptep->pte_high;
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ptep->pte_high = 0;
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return res;
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}
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#else
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#define native_ptep_get_and_clear(xp) native_local_ptep_get_and_clear(xp)
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#endif
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union split_pmd {
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struct {
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u32 pmd_low;
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u32 pmd_high;
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};
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pmd_t pmd;
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};
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#ifdef CONFIG_SMP
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static inline pmd_t native_pmdp_get_and_clear(pmd_t *pmdp)
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{
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union split_pmd res, *orig = (union split_pmd *)pmdp;
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/* xchg acts as a barrier before setting of the high bits */
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res.pmd_low = xchg(&orig->pmd_low, 0);
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res.pmd_high = orig->pmd_high;
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orig->pmd_high = 0;
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return res.pmd;
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}
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#else
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#define native_pmdp_get_and_clear(xp) native_local_pmdp_get_and_clear(xp)
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#endif
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#ifndef pmdp_establish
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#define pmdp_establish pmdp_establish
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static inline pmd_t pmdp_establish(struct vm_area_struct *vma,
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unsigned long address, pmd_t *pmdp, pmd_t pmd)
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{
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pmd_t old;
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/*
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* If pmd has present bit cleared we can get away without expensive
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* cmpxchg64: we can update pmdp half-by-half without racing with
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* anybody.
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*/
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if (!(pmd_val(pmd) & _PAGE_PRESENT)) {
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union split_pmd old, new, *ptr;
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ptr = (union split_pmd *)pmdp;
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new.pmd = pmd;
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/* xchg acts as a barrier before setting of the high bits */
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old.pmd_low = xchg(&ptr->pmd_low, new.pmd_low);
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old.pmd_high = ptr->pmd_high;
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ptr->pmd_high = new.pmd_high;
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return old.pmd;
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}
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do {
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old = *pmdp;
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} while (cmpxchg64(&pmdp->pmd, old.pmd, pmd.pmd) != old.pmd);
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return old;
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}
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#endif
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#ifdef CONFIG_SMP
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union split_pud {
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struct {
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u32 pud_low;
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u32 pud_high;
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};
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pud_t pud;
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};
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static inline pud_t native_pudp_get_and_clear(pud_t *pudp)
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{
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union split_pud res, *orig = (union split_pud *)pudp;
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/* xchg acts as a barrier before setting of the high bits */
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res.pud_low = xchg(&orig->pud_low, 0);
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res.pud_high = orig->pud_high;
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orig->pud_high = 0;
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return res.pud;
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}
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#else
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#define native_pudp_get_and_clear(xp) native_local_pudp_get_and_clear(xp)
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#endif
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/* Encode and de-code a swap entry */
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#define MAX_SWAPFILES_CHECK() BUILD_BUG_ON(MAX_SWAPFILES_SHIFT > 5)
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#define __swp_type(x) (((x).val) & 0x1f)
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#define __swp_offset(x) ((x).val >> 5)
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#define __swp_entry(type, offset) ((swp_entry_t){(type) | (offset) << 5})
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#define __pte_to_swp_entry(pte) ((swp_entry_t){ (pte).pte_high })
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#define __swp_entry_to_pte(x) ((pte_t){ { .pte_high = (x).val } })
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#define gup_get_pte gup_get_pte
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/*
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* WARNING: only to be used in the get_user_pages_fast() implementation.
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*
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* With get_user_pages_fast(), we walk down the pagetables without taking
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* any locks. For this we would like to load the pointers atomically,
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* but that is not possible (without expensive cmpxchg8b) on PAE. What
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* we do have is the guarantee that a PTE will only either go from not
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* present to present, or present to not present or both -- it will not
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* switch to a completely different present page without a TLB flush in
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* between; something that we are blocking by holding interrupts off.
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*
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* Setting ptes from not present to present goes:
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*
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* ptep->pte_high = h;
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* smp_wmb();
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* ptep->pte_low = l;
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*
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* And present to not present goes:
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*
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* ptep->pte_low = 0;
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* smp_wmb();
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* ptep->pte_high = 0;
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*
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* We must ensure here that the load of pte_low sees 'l' iff pte_high
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* sees 'h'. We load pte_high *after* loading pte_low, which ensures we
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* don't see an older value of pte_high. *Then* we recheck pte_low,
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* which ensures that we haven't picked up a changed pte high. We might
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* have gotten rubbish values from pte_low and pte_high, but we are
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* guaranteed that pte_low will not have the present bit set *unless*
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* it is 'l'. Because get_user_pages_fast() only operates on present ptes
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* we're safe.
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*/
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static inline pte_t gup_get_pte(pte_t *ptep)
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{
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pte_t pte;
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do {
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pte.pte_low = ptep->pte_low;
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smp_rmb();
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pte.pte_high = ptep->pte_high;
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smp_rmb();
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} while (unlikely(pte.pte_low != ptep->pte_low));
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return pte;
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}
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#endif /* _ASM_X86_PGTABLE_3LEVEL_H */
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