/* * This file is subject to the terms and conditions of the GNU General Public * License. See the file "COPYING" in the main directory of this archive * for more details. * * KVM/MIPS MMU handling in the KVM module. * * Copyright (C) 2012 MIPS Technologies, Inc. All rights reserved. * Authors: Sanjay Lal */ #include #include #include #include #include /* * KVM_MMU_CACHE_MIN_PAGES is the number of GPA page table translation levels * for which pages need to be cached. */ #if defined(__PAGETABLE_PMD_FOLDED) #define KVM_MMU_CACHE_MIN_PAGES 1 #else #define KVM_MMU_CACHE_MIN_PAGES 2 #endif void kvm_mmu_free_memory_caches(struct kvm_vcpu *vcpu) { kvm_mmu_free_memory_cache(&vcpu->arch.mmu_page_cache); } /** * kvm_pgd_init() - Initialise KVM GPA page directory. * @page: Pointer to page directory (PGD) for KVM GPA. * * Initialise a KVM GPA page directory with pointers to the invalid table, i.e. * representing no mappings. This is similar to pgd_init(), however it * initialises all the page directory pointers, not just the ones corresponding * to the userland address space (since it is for the guest physical address * space rather than a virtual address space). */ static void kvm_pgd_init(void *page) { unsigned long *p, *end; unsigned long entry; #ifdef __PAGETABLE_PMD_FOLDED entry = (unsigned long)invalid_pte_table; #else entry = (unsigned long)invalid_pmd_table; #endif p = (unsigned long *)page; end = p + PTRS_PER_PGD; do { p[0] = entry; p[1] = entry; p[2] = entry; p[3] = entry; p[4] = entry; p += 8; p[-3] = entry; p[-2] = entry; p[-1] = entry; } while (p != end); } /** * kvm_pgd_alloc() - Allocate and initialise a KVM GPA page directory. * * Allocate a blank KVM GPA page directory (PGD) for representing guest physical * to host physical page mappings. * * Returns: Pointer to new KVM GPA page directory. * NULL on allocation failure. */ pgd_t *kvm_pgd_alloc(void) { pgd_t *ret; ret = (pgd_t *)__get_free_pages(GFP_KERNEL, PGD_TABLE_ORDER); if (ret) kvm_pgd_init(ret); return ret; } /** * kvm_mips_walk_pgd() - Walk page table with optional allocation. * @pgd: Page directory pointer. * @addr: Address to index page table using. * @cache: MMU page cache to allocate new page tables from, or NULL. * * Walk the page tables pointed to by @pgd to find the PTE corresponding to the * address @addr. If page tables don't exist for @addr, they will be created * from the MMU cache if @cache is not NULL. * * Returns: Pointer to pte_t corresponding to @addr. * NULL if a page table doesn't exist for @addr and !@cache. * NULL if a page table allocation failed. */ static pte_t *kvm_mips_walk_pgd(pgd_t *pgd, struct kvm_mmu_memory_cache *cache, unsigned long addr) { p4d_t *p4d; pud_t *pud; pmd_t *pmd; pgd += pgd_index(addr); if (pgd_none(*pgd)) { /* Not used on MIPS yet */ BUG(); return NULL; } p4d = p4d_offset(pgd, addr); pud = pud_offset(p4d, addr); if (pud_none(*pud)) { pmd_t *new_pmd; if (!cache) return NULL; new_pmd = kvm_mmu_memory_cache_alloc(cache); pmd_init(new_pmd); pud_populate(NULL, pud, new_pmd); } pmd = pmd_offset(pud, addr); if (pmd_none(*pmd)) { pte_t *new_pte; if (!cache) return NULL; new_pte = kvm_mmu_memory_cache_alloc(cache); clear_page(new_pte); pmd_populate_kernel(NULL, pmd, new_pte); } return pte_offset_kernel(pmd, addr); } /* Caller must hold kvm->mm_lock */ static pte_t *kvm_mips_pte_for_gpa(struct kvm *kvm, struct kvm_mmu_memory_cache *cache, unsigned long addr) { return kvm_mips_walk_pgd(kvm->arch.gpa_mm.pgd, cache, addr); } /* * kvm_mips_flush_gpa_{pte,pmd,pud,pgd,pt}. * Flush a range of guest physical address space from the VM's GPA page tables. */ static bool kvm_mips_flush_gpa_pte(pte_t *pte, unsigned long start_gpa, unsigned long end_gpa) { int i_min = pte_index(start_gpa); int i_max = pte_index(end_gpa); bool safe_to_remove = (i_min == 0 && i_max == PTRS_PER_PTE - 1); int i; for (i = i_min; i <= i_max; ++i) { if (!pte_present(pte[i])) continue; set_pte(pte + i, __pte(0)); } return safe_to_remove; } static bool kvm_mips_flush_gpa_pmd(pmd_t *pmd, unsigned long start_gpa, unsigned long end_gpa) { pte_t *pte; unsigned long end = ~0ul; int i_min = pmd_index(start_gpa); int i_max = pmd_index(end_gpa); bool safe_to_remove = (i_min == 0 && i_max == PTRS_PER_PMD - 1); int i; for (i = i_min; i <= i_max; ++i, start_gpa = 0) { if (!pmd_present(pmd[i])) continue; pte = pte_offset_kernel(pmd + i, 0); if (i == i_max) end = end_gpa; if (kvm_mips_flush_gpa_pte(pte, start_gpa, end)) { pmd_clear(pmd + i); pte_free_kernel(NULL, pte); } else { safe_to_remove = false; } } return safe_to_remove; } static bool kvm_mips_flush_gpa_pud(pud_t *pud, unsigned long start_gpa, unsigned long end_gpa) { pmd_t *pmd; unsigned long end = ~0ul; int i_min = pud_index(start_gpa); int i_max = pud_index(end_gpa); bool safe_to_remove = (i_min == 0 && i_max == PTRS_PER_PUD - 1); int i; for (i = i_min; i <= i_max; ++i, start_gpa = 0) { if (!pud_present(pud[i])) continue; pmd = pmd_offset(pud + i, 0); if (i == i_max) end = end_gpa; if (kvm_mips_flush_gpa_pmd(pmd, start_gpa, end)) { pud_clear(pud + i); pmd_free(NULL, pmd); } else { safe_to_remove = false; } } return safe_to_remove; } static bool kvm_mips_flush_gpa_pgd(pgd_t *pgd, unsigned long start_gpa, unsigned long end_gpa) { p4d_t *p4d; pud_t *pud; unsigned long end = ~0ul; int i_min = pgd_index(start_gpa); int i_max = pgd_index(end_gpa); bool safe_to_remove = (i_min == 0 && i_max == PTRS_PER_PGD - 1); int i; for (i = i_min; i <= i_max; ++i, start_gpa = 0) { if (!pgd_present(pgd[i])) continue; p4d = p4d_offset(pgd, 0); pud = pud_offset(p4d + i, 0); if (i == i_max) end = end_gpa; if (kvm_mips_flush_gpa_pud(pud, start_gpa, end)) { pgd_clear(pgd + i); pud_free(NULL, pud); } else { safe_to_remove = false; } } return safe_to_remove; } /** * kvm_mips_flush_gpa_pt() - Flush a range of guest physical addresses. * @kvm: KVM pointer. * @start_gfn: Guest frame number of first page in GPA range to flush. * @end_gfn: Guest frame number of last page in GPA range to flush. * * Flushes a range of GPA mappings from the GPA page tables. * * The caller must hold the @kvm->mmu_lock spinlock. * * Returns: Whether its safe to remove the top level page directory because * all lower levels have been removed. */ bool kvm_mips_flush_gpa_pt(struct kvm *kvm, gfn_t start_gfn, gfn_t end_gfn) { return kvm_mips_flush_gpa_pgd(kvm->arch.gpa_mm.pgd, start_gfn << PAGE_SHIFT, end_gfn << PAGE_SHIFT); } #define BUILD_PTE_RANGE_OP(name, op) \ static int kvm_mips_##name##_pte(pte_t *pte, unsigned long start, \ unsigned long end) \ { \ int ret = 0; \ int i_min = pte_index(start); \ int i_max = pte_index(end); \ int i; \ pte_t old, new; \ \ for (i = i_min; i <= i_max; ++i) { \ if (!pte_present(pte[i])) \ continue; \ \ old = pte[i]; \ new = op(old); \ if (pte_val(new) == pte_val(old)) \ continue; \ set_pte(pte + i, new); \ ret = 1; \ } \ return ret; \ } \ \ /* returns true if anything was done */ \ static int kvm_mips_##name##_pmd(pmd_t *pmd, unsigned long start, \ unsigned long end) \ { \ int ret = 0; \ pte_t *pte; \ unsigned long cur_end = ~0ul; \ int i_min = pmd_index(start); \ int i_max = pmd_index(end); \ int i; \ \ for (i = i_min; i <= i_max; ++i, start = 0) { \ if (!pmd_present(pmd[i])) \ continue; \ \ pte = pte_offset_kernel(pmd + i, 0); \ if (i == i_max) \ cur_end = end; \ \ ret |= kvm_mips_##name##_pte(pte, start, cur_end); \ } \ return ret; \ } \ \ static int kvm_mips_##name##_pud(pud_t *pud, unsigned long start, \ unsigned long end) \ { \ int ret = 0; \ pmd_t *pmd; \ unsigned long cur_end = ~0ul; \ int i_min = pud_index(start); \ int i_max = pud_index(end); \ int i; \ \ for (i = i_min; i <= i_max; ++i, start = 0) { \ if (!pud_present(pud[i])) \ continue; \ \ pmd = pmd_offset(pud + i, 0); \ if (i == i_max) \ cur_end = end; \ \ ret |= kvm_mips_##name##_pmd(pmd, start, cur_end); \ } \ return ret; \ } \ \ static int kvm_mips_##name##_pgd(pgd_t *pgd, unsigned long start, \ unsigned long end) \ { \ int ret = 0; \ p4d_t *p4d; \ pud_t *pud; \ unsigned long cur_end = ~0ul; \ int i_min = pgd_index(start); \ int i_max = pgd_index(end); \ int i; \ \ for (i = i_min; i <= i_max; ++i, start = 0) { \ if (!pgd_present(pgd[i])) \ continue; \ \ p4d = p4d_offset(pgd, 0); \ pud = pud_offset(p4d + i, 0); \ if (i == i_max) \ cur_end = end; \ \ ret |= kvm_mips_##name##_pud(pud, start, cur_end); \ } \ return ret; \ } /* * kvm_mips_mkclean_gpa_pt. * Mark a range of guest physical address space clean (writes fault) in the VM's * GPA page table to allow dirty page tracking. */ BUILD_PTE_RANGE_OP(mkclean, pte_mkclean) /** * kvm_mips_mkclean_gpa_pt() - Make a range of guest physical addresses clean. * @kvm: KVM pointer. * @start_gfn: Guest frame number of first page in GPA range to flush. * @end_gfn: Guest frame number of last page in GPA range to flush. * * Make a range of GPA mappings clean so that guest writes will fault and * trigger dirty page logging. * * The caller must hold the @kvm->mmu_lock spinlock. * * Returns: Whether any GPA mappings were modified, which would require * derived mappings (GVA page tables & TLB enties) to be * invalidated. */ int kvm_mips_mkclean_gpa_pt(struct kvm *kvm, gfn_t start_gfn, gfn_t end_gfn) { return kvm_mips_mkclean_pgd(kvm->arch.gpa_mm.pgd, start_gfn << PAGE_SHIFT, end_gfn << PAGE_SHIFT); } /** * kvm_arch_mmu_enable_log_dirty_pt_masked() - write protect dirty pages * @kvm: The KVM pointer * @slot: The memory slot associated with mask * @gfn_offset: The gfn offset in memory slot * @mask: The mask of dirty pages at offset 'gfn_offset' in this memory * slot to be write protected * * Walks bits set in mask write protects the associated pte's. Caller must * acquire @kvm->mmu_lock. */ void kvm_arch_mmu_enable_log_dirty_pt_masked(struct kvm *kvm, struct kvm_memory_slot *slot, gfn_t gfn_offset, unsigned long mask) { gfn_t base_gfn = slot->base_gfn + gfn_offset; gfn_t start = base_gfn + __ffs(mask); gfn_t end = base_gfn + __fls(mask); kvm_mips_mkclean_gpa_pt(kvm, start, end); } /* * kvm_mips_mkold_gpa_pt. * Mark a range of guest physical address space old (all accesses fault) in the * VM's GPA page table to allow detection of commonly used pages. */ BUILD_PTE_RANGE_OP(mkold, pte_mkold) static int kvm_mips_mkold_gpa_pt(struct kvm *kvm, gfn_t start_gfn, gfn_t end_gfn) { return kvm_mips_mkold_pgd(kvm->arch.gpa_mm.pgd, start_gfn << PAGE_SHIFT, end_gfn << PAGE_SHIFT); } bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range) { kvm_mips_flush_gpa_pt(kvm, range->start, range->end); return true; } bool kvm_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range) { return kvm_mips_mkold_gpa_pt(kvm, range->start, range->end); } bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range) { gpa_t gpa = range->start << PAGE_SHIFT; pte_t *gpa_pte = kvm_mips_pte_for_gpa(kvm, NULL, gpa); if (!gpa_pte) return false; return pte_young(*gpa_pte); } /** * _kvm_mips_map_page_fast() - Fast path GPA fault handler. * @vcpu: VCPU pointer. * @gpa: Guest physical address of fault. * @write_fault: Whether the fault was due to a write. * @out_entry: New PTE for @gpa (written on success unless NULL). * @out_buddy: New PTE for @gpa's buddy (written on success unless * NULL). * * Perform fast path GPA fault handling, doing all that can be done without * calling into KVM. This handles marking old pages young (for idle page * tracking), and dirtying of clean pages (for dirty page logging). * * Returns: 0 on success, in which case we can update derived mappings and * resume guest execution. * -EFAULT on failure due to absent GPA mapping or write to * read-only page, in which case KVM must be consulted. */ static int _kvm_mips_map_page_fast(struct kvm_vcpu *vcpu, unsigned long gpa, bool write_fault, pte_t *out_entry, pte_t *out_buddy) { struct kvm *kvm = vcpu->kvm; gfn_t gfn = gpa >> PAGE_SHIFT; pte_t *ptep; int ret = 0; spin_lock(&kvm->mmu_lock); /* Fast path - just check GPA page table for an existing entry */ ptep = kvm_mips_pte_for_gpa(kvm, NULL, gpa); if (!ptep || !pte_present(*ptep)) { ret = -EFAULT; goto out; } /* Track access to pages marked old */ if (!pte_young(*ptep)) set_pte(ptep, pte_mkyoung(*ptep)); if (write_fault && !pte_dirty(*ptep)) { if (!pte_write(*ptep)) { ret = -EFAULT; goto out; } /* Track dirtying of writeable pages */ set_pte(ptep, pte_mkdirty(*ptep)); mark_page_dirty(kvm, gfn); } if (out_entry) *out_entry = *ptep; if (out_buddy) *out_buddy = *ptep_buddy(ptep); out: spin_unlock(&kvm->mmu_lock); return ret; } /** * kvm_mips_map_page() - Map a guest physical page. * @vcpu: VCPU pointer. * @gpa: Guest physical address of fault. * @write_fault: Whether the fault was due to a write. * @out_entry: New PTE for @gpa (written on success unless NULL). * @out_buddy: New PTE for @gpa's buddy (written on success unless * NULL). * * Handle GPA faults by creating a new GPA mapping (or updating an existing * one). * * This takes care of marking pages young or dirty (idle/dirty page tracking), * asking KVM for the corresponding PFN, and creating a mapping in the GPA page * tables. Derived mappings (GVA page tables and TLBs) must be handled by the * caller. * * Returns: 0 on success, in which case the caller may use the @out_entry * and @out_buddy PTEs to update derived mappings and resume guest * execution. * -EFAULT if there is no memory region at @gpa or a write was * attempted to a read-only memory region. This is usually handled * as an MMIO access. */ static int kvm_mips_map_page(struct kvm_vcpu *vcpu, unsigned long gpa, bool write_fault, pte_t *out_entry, pte_t *out_buddy) { struct kvm *kvm = vcpu->kvm; struct kvm_mmu_memory_cache *memcache = &vcpu->arch.mmu_page_cache; gfn_t gfn = gpa >> PAGE_SHIFT; int srcu_idx, err; kvm_pfn_t pfn; pte_t *ptep, entry; bool writeable; unsigned long prot_bits; unsigned long mmu_seq; struct page *page; /* Try the fast path to handle old / clean pages */ srcu_idx = srcu_read_lock(&kvm->srcu); err = _kvm_mips_map_page_fast(vcpu, gpa, write_fault, out_entry, out_buddy); if (!err) goto out; /* We need a minimum of cached pages ready for page table creation */ err = kvm_mmu_topup_memory_cache(memcache, KVM_MMU_CACHE_MIN_PAGES); if (err) goto out; retry: /* * Used to check for invalidations in progress, of the pfn that is * returned by pfn_to_pfn_prot below. */ mmu_seq = kvm->mmu_invalidate_seq; /* * Ensure the read of mmu_invalidate_seq isn't reordered with PTE reads * in kvm_faultin_pfn() (which calls get_user_pages()), so that we don't * risk the page we get a reference to getting unmapped before we have a * chance to grab the mmu_lock without mmu_invalidate_retry() noticing. * * This smp_rmb() pairs with the effective smp_wmb() of the combination * of the pte_unmap_unlock() after the PTE is zapped, and the * spin_lock() in kvm_mmu_notifier_invalidate_() before * mmu_invalidate_seq is incremented. */ smp_rmb(); /* Slow path - ask KVM core whether we can access this GPA */ pfn = kvm_faultin_pfn(vcpu, gfn, write_fault, &writeable, &page); if (is_error_noslot_pfn(pfn)) { err = -EFAULT; goto out; } spin_lock(&kvm->mmu_lock); /* Check if an invalidation has taken place since we got pfn */ if (mmu_invalidate_retry(kvm, mmu_seq)) { /* * This can happen when mappings are changed asynchronously, but * also synchronously if a COW is triggered by * kvm_faultin_pfn(). */ spin_unlock(&kvm->mmu_lock); kvm_release_page_unused(page); goto retry; } /* Ensure page tables are allocated */ ptep = kvm_mips_pte_for_gpa(kvm, memcache, gpa); /* Set up the PTE */ prot_bits = _PAGE_PRESENT | __READABLE | _page_cachable_default; if (writeable) { prot_bits |= _PAGE_WRITE; if (write_fault) { prot_bits |= __WRITEABLE; mark_page_dirty(kvm, gfn); } } entry = pfn_pte(pfn, __pgprot(prot_bits)); /* Write the PTE */ set_pte(ptep, entry); err = 0; if (out_entry) *out_entry = *ptep; if (out_buddy) *out_buddy = *ptep_buddy(ptep); kvm_release_faultin_page(kvm, page, false, writeable); spin_unlock(&kvm->mmu_lock); out: srcu_read_unlock(&kvm->srcu, srcu_idx); return err; } int kvm_mips_handle_vz_root_tlb_fault(unsigned long badvaddr, struct kvm_vcpu *vcpu, bool write_fault) { int ret; ret = kvm_mips_map_page(vcpu, badvaddr, write_fault, NULL, NULL); if (ret) return ret; /* Invalidate this entry in the TLB */ return kvm_vz_host_tlb_inv(vcpu, badvaddr); } /** * kvm_mips_migrate_count() - Migrate timer. * @vcpu: Virtual CPU. * * Migrate CP0_Count hrtimer to the current CPU by cancelling and restarting it * if it was running prior to being cancelled. * * Must be called when the VCPU is migrated to a different CPU to ensure that * timer expiry during guest execution interrupts the guest and causes the * interrupt to be delivered in a timely manner. */ static void kvm_mips_migrate_count(struct kvm_vcpu *vcpu) { if (hrtimer_cancel(&vcpu->arch.comparecount_timer)) hrtimer_restart(&vcpu->arch.comparecount_timer); } /* Restore ASID once we are scheduled back after preemption */ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) { unsigned long flags; kvm_debug("%s: vcpu %p, cpu: %d\n", __func__, vcpu, cpu); local_irq_save(flags); vcpu->cpu = cpu; if (vcpu->arch.last_sched_cpu != cpu) { kvm_debug("[%d->%d]KVM VCPU[%d] switch\n", vcpu->arch.last_sched_cpu, cpu, vcpu->vcpu_id); /* * Migrate the timer interrupt to the current CPU so that it * always interrupts the guest and synchronously triggers a * guest timer interrupt. */ kvm_mips_migrate_count(vcpu); } /* restore guest state to registers */ kvm_mips_callbacks->vcpu_load(vcpu, cpu); local_irq_restore(flags); } /* ASID can change if another task is scheduled during preemption */ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu) { unsigned long flags; int cpu; local_irq_save(flags); cpu = smp_processor_id(); vcpu->arch.last_sched_cpu = cpu; vcpu->cpu = -1; /* save guest state in registers */ kvm_mips_callbacks->vcpu_put(vcpu, cpu); local_irq_restore(flags); }