diff options
Diffstat (limited to 'virt')
| -rw-r--r-- | virt/kvm/arm/mmu.c | 9 | ||||
| -rw-r--r-- | virt/kvm/kvm_main.c | 210 |
2 files changed, 165 insertions, 54 deletions
diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c index 8f22efa095f4..e3b9ee268823 100644 --- a/virt/kvm/arm/mmu.c +++ b/virt/kvm/arm/mmu.c @@ -1534,8 +1534,13 @@ void kvm_mmu_wp_memory_region(struct kvm *kvm, int slot) { struct kvm_memslots *slots = kvm_memslots(kvm); struct kvm_memory_slot *memslot = id_to_memslot(slots, slot); - phys_addr_t start = memslot->base_gfn << PAGE_SHIFT; - phys_addr_t end = (memslot->base_gfn + memslot->npages) << PAGE_SHIFT; + phys_addr_t start, end; + + if (WARN_ON_ONCE(!memslot)) + return; + + start = memslot->base_gfn << PAGE_SHIFT; + end = (memslot->base_gfn + memslot->npages) << PAGE_SHIFT; spin_lock(&kvm->mmu_lock); stage2_wp_range(kvm, start, end); diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index c115b78e85c3..62e45c64e443 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -566,7 +566,7 @@ static struct kvm_memslots *kvm_alloc_memslots(void) return NULL; for (i = 0; i < KVM_MEM_SLOTS_NUM; i++) - slots->id_to_index[i] = slots->memslots[i].id = i; + slots->id_to_index[i] = slots->memslots[i].id = -1; return slots; } @@ -870,63 +870,162 @@ static int kvm_create_dirty_bitmap(struct kvm_memory_slot *memslot) } /* - * Insert memslot and re-sort memslots based on their GFN, - * so binary search could be used to lookup GFN. - * Sorting algorithm takes advantage of having initially - * sorted array and known changed memslot position. + * Delete a memslot by decrementing the number of used slots and shifting all + * other entries in the array forward one spot. */ -static void update_memslots(struct kvm_memslots *slots, - struct kvm_memory_slot *new, - enum kvm_mr_change change) +static inline void kvm_memslot_delete(struct kvm_memslots *slots, + struct kvm_memory_slot *memslot) { - int id = new->id; - int i = slots->id_to_index[id]; struct kvm_memory_slot *mslots = slots->memslots; + int i; - WARN_ON(mslots[i].id != id); - switch (change) { - case KVM_MR_CREATE: - slots->used_slots++; - WARN_ON(mslots[i].npages || !new->npages); - break; - case KVM_MR_DELETE: - slots->used_slots--; - WARN_ON(new->npages || !mslots[i].npages); - break; - default: - break; - } + if (WARN_ON(slots->id_to_index[memslot->id] == -1)) + return; - while (i < KVM_MEM_SLOTS_NUM - 1 && - new->base_gfn <= mslots[i + 1].base_gfn) { - if (!mslots[i + 1].npages) - break; + slots->used_slots--; + + for (i = slots->id_to_index[memslot->id]; i < slots->used_slots; i++) { mslots[i] = mslots[i + 1]; slots->id_to_index[mslots[i].id] = i; - i++; } + mslots[i] = *memslot; + slots->id_to_index[memslot->id] = -1; +} + +/* + * "Insert" a new memslot by incrementing the number of used slots. Returns + * the new slot's initial index into the memslots array. + */ +static inline int kvm_memslot_insert_back(struct kvm_memslots *slots) +{ + return slots->used_slots++; +} + +/* + * Move a changed memslot backwards in the array by shifting existing slots + * with a higher GFN toward the front of the array. Note, the changed memslot + * itself is not preserved in the array, i.e. not swapped at this time, only + * its new index into the array is tracked. Returns the changed memslot's + * current index into the memslots array. + */ +static inline int kvm_memslot_move_backward(struct kvm_memslots *slots, + struct kvm_memory_slot *memslot) +{ + struct kvm_memory_slot *mslots = slots->memslots; + int i; + + if (WARN_ON_ONCE(slots->id_to_index[memslot->id] == -1) || + WARN_ON_ONCE(!slots->used_slots)) + return -1; /* - * The ">=" is needed when creating a slot with base_gfn == 0, - * so that it moves before all those with base_gfn == npages == 0. - * - * On the other hand, if new->npages is zero, the above loop has - * already left i pointing to the beginning of the empty part of - * mslots, and the ">=" would move the hole backwards in this - * case---which is wrong. So skip the loop when deleting a slot. + * Move the target memslot backward in the array by shifting existing + * memslots with a higher GFN (than the target memslot) towards the + * front of the array. */ - if (new->npages) { - while (i > 0 && - new->base_gfn >= mslots[i - 1].base_gfn) { - mslots[i] = mslots[i - 1]; - slots->id_to_index[mslots[i].id] = i; - i--; - } - } else - WARN_ON_ONCE(i != slots->used_slots); + for (i = slots->id_to_index[memslot->id]; i < slots->used_slots - 1; i++) { + if (memslot->base_gfn > mslots[i + 1].base_gfn) + break; + + WARN_ON_ONCE(memslot->base_gfn == mslots[i + 1].base_gfn); + + /* Shift the next memslot forward one and update its index. */ + mslots[i] = mslots[i + 1]; + slots->id_to_index[mslots[i].id] = i; + } + return i; +} + +/* + * Move a changed memslot forwards in the array by shifting existing slots with + * a lower GFN toward the back of the array. Note, the changed memslot itself + * is not preserved in the array, i.e. not swapped at this time, only its new + * index into the array is tracked. Returns the changed memslot's final index + * into the memslots array. + */ +static inline int kvm_memslot_move_forward(struct kvm_memslots *slots, + struct kvm_memory_slot *memslot, + int start) +{ + struct kvm_memory_slot *mslots = slots->memslots; + int i; + + for (i = start; i > 0; i--) { + if (memslot->base_gfn < mslots[i - 1].base_gfn) + break; + + WARN_ON_ONCE(memslot->base_gfn == mslots[i - 1].base_gfn); - mslots[i] = *new; - slots->id_to_index[mslots[i].id] = i; + /* Shift the next memslot back one and update its index. */ + mslots[i] = mslots[i - 1]; + slots->id_to_index[mslots[i].id] = i; + } + return i; +} + +/* + * Re-sort memslots based on their GFN to account for an added, deleted, or + * moved memslot. Sorting memslots by GFN allows using a binary search during + * memslot lookup. + * + * IMPORTANT: Slots are sorted from highest GFN to lowest GFN! I.e. the entry + * at memslots[0] has the highest GFN. + * + * The sorting algorithm takes advantage of having initially sorted memslots + * and knowing the position of the changed memslot. Sorting is also optimized + * by not swapping the updated memslot and instead only shifting other memslots + * and tracking the new index for the update memslot. Only once its final + * index is known is the updated memslot copied into its position in the array. + * + * - When deleting a memslot, the deleted memslot simply needs to be moved to + * the end of the array. + * + * - When creating a memslot, the algorithm "inserts" the new memslot at the + * end of the array and then it forward to its correct location. + * + * - When moving a memslot, the algorithm first moves the updated memslot + * backward to handle the scenario where the memslot's GFN was changed to a + * lower value. update_memslots() then falls through and runs the same flow + * as creating a memslot to move the memslot forward to handle the scenario + * where its GFN was changed to a higher value. + * + * Note, slots are sorted from highest->lowest instead of lowest->highest for + * historical reasons. Originally, invalid memslots where denoted by having + * GFN=0, thus sorting from highest->lowest naturally sorted invalid memslots + * to the end of the array. The current algorithm uses dedicated logic to + * delete a memslot and thus does not rely on invalid memslots having GFN=0. + * + * The other historical motiviation for highest->lowest was to improve the + * performance of memslot lookup. KVM originally used a linear search starting + * at memslots[0]. On x86, the largest memslot usually has one of the highest, + * if not *the* highest, GFN, as the bulk of the guest's RAM is located in a + * single memslot above the 4gb boundary. As the largest memslot is also the + * most likely to be referenced, sorting it to the front of the array was + * advantageous. The current binary search starts from the middle of the array + * and uses an LRU pointer to improve performance for all memslots and GFNs. + */ +static void update_memslots(struct kvm_memslots *slots, + struct kvm_memory_slot *memslot, + enum kvm_mr_change change) +{ + int i; + + if (change == KVM_MR_DELETE) { + kvm_memslot_delete(slots, memslot); + } else { + if (change == KVM_MR_CREATE) + i = kvm_memslot_insert_back(slots); + else + i = kvm_memslot_move_backward(slots, memslot); + i = kvm_memslot_move_forward(slots, memslot, i); + + /* + * Copy the memslot to its new position in memslots and update + * its index accordingly. + */ + slots->memslots[i] = *memslot; + slots->id_to_index[memslot->id] = i; + } } static int check_memory_region_flags(const struct kvm_userspace_memory_region *mem) @@ -1106,7 +1205,14 @@ int __kvm_set_memory_region(struct kvm *kvm, * memslot needs to be referenced after calling update_memslots(), e.g. * to free its resources and for arch specific behavior. */ - old = *id_to_memslot(__kvm_memslots(kvm, as_id), id); + tmp = id_to_memslot(__kvm_memslots(kvm, as_id), id); + if (tmp) { + old = *tmp; + tmp = NULL; + } else { + memset(&old, 0, sizeof(old)); + old.id = id; + } if (!mem->memory_size) return kvm_delete_memslot(kvm, mem, &old, as_id); @@ -1224,7 +1330,7 @@ int kvm_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log, slots = __kvm_memslots(kvm, as_id); *memslot = id_to_memslot(slots, id); - if (!(*memslot)->dirty_bitmap) + if (!(*memslot) || !(*memslot)->dirty_bitmap) return -ENOENT; kvm_arch_sync_dirty_log(kvm, *memslot); @@ -1282,10 +1388,10 @@ static int kvm_get_dirty_log_protect(struct kvm *kvm, struct kvm_dirty_log *log) slots = __kvm_memslots(kvm, as_id); memslot = id_to_memslot(slots, id); + if (!memslot || !memslot->dirty_bitmap) + return -ENOENT; dirty_bitmap = memslot->dirty_bitmap; - if (!dirty_bitmap) - return -ENOENT; kvm_arch_sync_dirty_log(kvm, memslot); @@ -1393,10 +1499,10 @@ static int kvm_clear_dirty_log_protect(struct kvm *kvm, slots = __kvm_memslots(kvm, as_id); memslot = id_to_memslot(slots, id); + if (!memslot || !memslot->dirty_bitmap) + return -ENOENT; dirty_bitmap = memslot->dirty_bitmap; - if (!dirty_bitmap) - return -ENOENT; n = ALIGN(log->num_pages, BITS_PER_LONG) / 8; |