diff options
Diffstat (limited to 'arch/arm64/kvm/hyp/nvhe/page_alloc.c')
-rw-r--r-- | arch/arm64/kvm/hyp/nvhe/page_alloc.c | 262 |
1 files changed, 262 insertions, 0 deletions
diff --git a/arch/arm64/kvm/hyp/nvhe/page_alloc.c b/arch/arm64/kvm/hyp/nvhe/page_alloc.c new file mode 100644 index 000000000..d40f0b30b --- /dev/null +++ b/arch/arm64/kvm/hyp/nvhe/page_alloc.c @@ -0,0 +1,262 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (C) 2020 Google LLC + * Author: Quentin Perret <qperret@google.com> + */ + +#include <asm/kvm_hyp.h> +#include <nvhe/gfp.h> + +u64 __hyp_vmemmap; + +/* + * Index the hyp_vmemmap to find a potential buddy page, but make no assumption + * about its current state. + * + * Example buddy-tree for a 4-pages physically contiguous pool: + * + * o : Page 3 + * / + * o-o : Page 2 + * / + * / o : Page 1 + * / / + * o---o-o : Page 0 + * Order 2 1 0 + * + * Example of requests on this pool: + * __find_buddy_nocheck(pool, page 0, order 0) => page 1 + * __find_buddy_nocheck(pool, page 0, order 1) => page 2 + * __find_buddy_nocheck(pool, page 1, order 0) => page 0 + * __find_buddy_nocheck(pool, page 2, order 0) => page 3 + */ +static struct hyp_page *__find_buddy_nocheck(struct hyp_pool *pool, + struct hyp_page *p, + unsigned short order) +{ + phys_addr_t addr = hyp_page_to_phys(p); + + addr ^= (PAGE_SIZE << order); + + /* + * Don't return a page outside the pool range -- it belongs to + * something else and may not be mapped in hyp_vmemmap. + */ + if (addr < pool->range_start || addr >= pool->range_end) + return NULL; + + return hyp_phys_to_page(addr); +} + +/* Find a buddy page currently available for allocation */ +static struct hyp_page *__find_buddy_avail(struct hyp_pool *pool, + struct hyp_page *p, + unsigned short order) +{ + struct hyp_page *buddy = __find_buddy_nocheck(pool, p, order); + + if (!buddy || buddy->order != order || buddy->refcount) + return NULL; + + return buddy; + +} + +/* + * Pages that are available for allocation are tracked in free-lists, so we use + * the pages themselves to store the list nodes to avoid wasting space. As the + * allocator always returns zeroed pages (which are zeroed on the hyp_put_page() + * path to optimize allocation speed), we also need to clean-up the list node in + * each page when we take it out of the list. + */ +static inline void page_remove_from_list(struct hyp_page *p) +{ + struct list_head *node = hyp_page_to_virt(p); + + __list_del_entry(node); + memset(node, 0, sizeof(*node)); +} + +static inline void page_add_to_list(struct hyp_page *p, struct list_head *head) +{ + struct list_head *node = hyp_page_to_virt(p); + + INIT_LIST_HEAD(node); + list_add_tail(node, head); +} + +static inline struct hyp_page *node_to_page(struct list_head *node) +{ + return hyp_virt_to_page(node); +} + +static void __hyp_attach_page(struct hyp_pool *pool, + struct hyp_page *p) +{ + unsigned short order = p->order; + struct hyp_page *buddy; + + memset(hyp_page_to_virt(p), 0, PAGE_SIZE << p->order); + + /* + * Only the first struct hyp_page of a high-order page (otherwise known + * as the 'head') should have p->order set. The non-head pages should + * have p->order = HYP_NO_ORDER. Here @p may no longer be the head + * after coalescing, so make sure to mark it HYP_NO_ORDER proactively. + */ + p->order = HYP_NO_ORDER; + for (; (order + 1) < pool->max_order; order++) { + buddy = __find_buddy_avail(pool, p, order); + if (!buddy) + break; + + /* Take the buddy out of its list, and coalesce with @p */ + page_remove_from_list(buddy); + buddy->order = HYP_NO_ORDER; + p = min(p, buddy); + } + + /* Mark the new head, and insert it */ + p->order = order; + page_add_to_list(p, &pool->free_area[order]); +} + +static struct hyp_page *__hyp_extract_page(struct hyp_pool *pool, + struct hyp_page *p, + unsigned short order) +{ + struct hyp_page *buddy; + + page_remove_from_list(p); + while (p->order > order) { + /* + * The buddy of order n - 1 currently has HYP_NO_ORDER as it + * is covered by a higher-level page (whose head is @p). Use + * __find_buddy_nocheck() to find it and inject it in the + * free_list[n - 1], effectively splitting @p in half. + */ + p->order--; + buddy = __find_buddy_nocheck(pool, p, p->order); + buddy->order = p->order; + page_add_to_list(buddy, &pool->free_area[buddy->order]); + } + + return p; +} + +static inline void hyp_page_ref_inc(struct hyp_page *p) +{ + BUG_ON(p->refcount == USHRT_MAX); + p->refcount++; +} + +static inline int hyp_page_ref_dec_and_test(struct hyp_page *p) +{ + BUG_ON(!p->refcount); + p->refcount--; + return (p->refcount == 0); +} + +static inline void hyp_set_page_refcounted(struct hyp_page *p) +{ + BUG_ON(p->refcount); + p->refcount = 1; +} + +static void __hyp_put_page(struct hyp_pool *pool, struct hyp_page *p) +{ + if (hyp_page_ref_dec_and_test(p)) + __hyp_attach_page(pool, p); +} + +/* + * Changes to the buddy tree and page refcounts must be done with the hyp_pool + * lock held. If a refcount change requires an update to the buddy tree (e.g. + * hyp_put_page()), both operations must be done within the same critical + * section to guarantee transient states (e.g. a page with null refcount but + * not yet attached to a free list) can't be observed by well-behaved readers. + */ +void hyp_put_page(struct hyp_pool *pool, void *addr) +{ + struct hyp_page *p = hyp_virt_to_page(addr); + + hyp_spin_lock(&pool->lock); + __hyp_put_page(pool, p); + hyp_spin_unlock(&pool->lock); +} + +void hyp_get_page(struct hyp_pool *pool, void *addr) +{ + struct hyp_page *p = hyp_virt_to_page(addr); + + hyp_spin_lock(&pool->lock); + hyp_page_ref_inc(p); + hyp_spin_unlock(&pool->lock); +} + +void hyp_split_page(struct hyp_page *p) +{ + unsigned short order = p->order; + unsigned int i; + + p->order = 0; + for (i = 1; i < (1 << order); i++) { + struct hyp_page *tail = p + i; + + tail->order = 0; + hyp_set_page_refcounted(tail); + } +} + +void *hyp_alloc_pages(struct hyp_pool *pool, unsigned short order) +{ + unsigned short i = order; + struct hyp_page *p; + + hyp_spin_lock(&pool->lock); + + /* Look for a high-enough-order page */ + while (i < pool->max_order && list_empty(&pool->free_area[i])) + i++; + if (i >= pool->max_order) { + hyp_spin_unlock(&pool->lock); + return NULL; + } + + /* Extract it from the tree at the right order */ + p = node_to_page(pool->free_area[i].next); + p = __hyp_extract_page(pool, p, order); + + hyp_set_page_refcounted(p); + hyp_spin_unlock(&pool->lock); + + return hyp_page_to_virt(p); +} + +int hyp_pool_init(struct hyp_pool *pool, u64 pfn, unsigned int nr_pages, + unsigned int reserved_pages) +{ + phys_addr_t phys = hyp_pfn_to_phys(pfn); + struct hyp_page *p; + int i; + + hyp_spin_lock_init(&pool->lock); + pool->max_order = min(MAX_ORDER, get_order((nr_pages + 1) << PAGE_SHIFT)); + for (i = 0; i < pool->max_order; i++) + INIT_LIST_HEAD(&pool->free_area[i]); + pool->range_start = phys; + pool->range_end = phys + (nr_pages << PAGE_SHIFT); + + /* Init the vmemmap portion */ + p = hyp_phys_to_page(phys); + for (i = 0; i < nr_pages; i++) { + p[i].order = 0; + hyp_set_page_refcounted(&p[i]); + } + + /* Attach the unused pages to the buddy tree */ + for (i = reserved_pages; i < nr_pages; i++) + __hyp_put_page(pool, &p[i]); + + return 0; +} |