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memremap.c
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memremap.c
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/* SPDX-License-Identifier: GPL-2.0 */
/* Copyright(c) 2015 Intel Corporation. All rights reserved. */
#include <linux/device.h>
#include <linux/io.h>
#include <linux/kasan.h>
#include <linux/memory_hotplug.h>
#include <linux/mm.h>
#include <linux/pfn_t.h>
#include <linux/swap.h>
#include <linux/mmzone.h>
#include <linux/swapops.h>
#include <linux/types.h>
#include <linux/wait_bit.h>
#include <linux/xarray.h>
static DEFINE_XARRAY(pgmap_array);
/*
* The memremap() and memremap_pages() interfaces are alternately used
* to map persistent memory namespaces. These interfaces place different
* constraints on the alignment and size of the mapping (namespace).
* memremap() can map individual PAGE_SIZE pages. memremap_pages() can
* only map subsections (2MB), and at least one architecture (PowerPC)
* the minimum mapping granularity of memremap_pages() is 16MB.
*
* The role of memremap_compat_align() is to communicate the minimum
* arch supported alignment of a namespace such that it can freely
* switch modes without violating the arch constraint. Namely, do not
* allow a namespace to be PAGE_SIZE aligned since that namespace may be
* reconfigured into a mode that requires SUBSECTION_SIZE alignment.
*/
#ifndef CONFIG_ARCH_HAS_MEMREMAP_COMPAT_ALIGN
unsigned long memremap_compat_align(void)
{
return SUBSECTION_SIZE;
}
EXPORT_SYMBOL_GPL(memremap_compat_align);
#endif
#ifdef CONFIG_DEV_PAGEMAP_OPS
DEFINE_STATIC_KEY_FALSE(devmap_managed_key);
EXPORT_SYMBOL(devmap_managed_key);
static atomic_t devmap_managed_enable;
static void devmap_managed_enable_put(void)
{
if (atomic_dec_and_test(&devmap_managed_enable))
static_branch_disable(&devmap_managed_key);
}
static int devmap_managed_enable_get(struct dev_pagemap *pgmap)
{
if (pgmap->type == MEMORY_DEVICE_PRIVATE &&
(!pgmap->ops || !pgmap->ops->page_free)) {
WARN(1, "Missing page_free method\n");
return -EINVAL;
}
if (atomic_inc_return(&devmap_managed_enable) == 1)
static_branch_enable(&devmap_managed_key);
return 0;
}
#else
static int devmap_managed_enable_get(struct dev_pagemap *pgmap)
{
return -EINVAL;
}
static void devmap_managed_enable_put(void)
{
}
#endif /* CONFIG_DEV_PAGEMAP_OPS */
static void pgmap_array_delete(struct resource *res)
{
xa_store_range(&pgmap_array, PHYS_PFN(res->start), PHYS_PFN(res->end),
NULL, GFP_KERNEL);
synchronize_rcu();
}
static unsigned long pfn_first(struct dev_pagemap *pgmap)
{
return PHYS_PFN(pgmap->res.start) +
vmem_altmap_offset(pgmap_altmap(pgmap));
}
static unsigned long pfn_end(struct dev_pagemap *pgmap)
{
const struct resource *res = &pgmap->res;
return (res->start + resource_size(res)) >> PAGE_SHIFT;
}
static unsigned long pfn_next(unsigned long pfn)
{
if (pfn % 1024 == 0)
cond_resched();
return pfn + 1;
}
#define for_each_device_pfn(pfn, map) \
for (pfn = pfn_first(map); pfn < pfn_end(map); pfn = pfn_next(pfn))
static void dev_pagemap_kill(struct dev_pagemap *pgmap)
{
if (pgmap->ops && pgmap->ops->kill)
pgmap->ops->kill(pgmap);
else
percpu_ref_kill(pgmap->ref);
}
static void dev_pagemap_cleanup(struct dev_pagemap *pgmap)
{
if (pgmap->ops && pgmap->ops->cleanup) {
pgmap->ops->cleanup(pgmap);
} else {
wait_for_completion(&pgmap->done);
percpu_ref_exit(pgmap->ref);
}
/*
* Undo the pgmap ref assignment for the internal case as the
* caller may re-enable the same pgmap.
*/
if (pgmap->ref == &pgmap->internal_ref)
pgmap->ref = NULL;
}
void memunmap_pages(struct dev_pagemap *pgmap)
{
struct resource *res = &pgmap->res;
struct page *first_page;
unsigned long pfn;
int nid;
dev_pagemap_kill(pgmap);
for_each_device_pfn(pfn, pgmap)
put_page(pfn_to_page(pfn));
dev_pagemap_cleanup(pgmap);
/* make sure to access a memmap that was actually initialized */
first_page = pfn_to_page(pfn_first(pgmap));
/* pages are dead and unused, undo the arch mapping */
nid = page_to_nid(first_page);
mem_hotplug_begin();
remove_pfn_range_from_zone(page_zone(first_page), PHYS_PFN(res->start),
PHYS_PFN(resource_size(res)));
if (pgmap->type == MEMORY_DEVICE_PRIVATE) {
__remove_pages(PHYS_PFN(res->start),
PHYS_PFN(resource_size(res)), NULL);
} else {
arch_remove_memory(nid, res->start, resource_size(res),
pgmap_altmap(pgmap));
kasan_remove_zero_shadow(__va(res->start), resource_size(res));
}
mem_hotplug_done();
untrack_pfn(NULL, PHYS_PFN(res->start), resource_size(res));
pgmap_array_delete(res);
WARN_ONCE(pgmap->altmap.alloc, "failed to free all reserved pages\n");
devmap_managed_enable_put();
}
EXPORT_SYMBOL_GPL(memunmap_pages);
static void devm_memremap_pages_release(void *data)
{
memunmap_pages(data);
}
static void dev_pagemap_percpu_release(struct percpu_ref *ref)
{
struct dev_pagemap *pgmap =
container_of(ref, struct dev_pagemap, internal_ref);
complete(&pgmap->done);
}
/*
* Not device managed version of dev_memremap_pages, undone by
* memunmap_pages(). Please use dev_memremap_pages if you have a struct
* device available.
*/
void *memremap_pages(struct dev_pagemap *pgmap, int nid)
{
struct resource *res = &pgmap->res;
struct dev_pagemap *conflict_pgmap;
struct mhp_params params = {
/*
* We do not want any optional features only our own memmap
*/
.altmap = pgmap_altmap(pgmap),
};
pgprot_t pgprot = PAGE_KERNEL;
int error, is_ram;
bool need_devmap_managed = true;
switch (pgmap->type) {
case MEMORY_DEVICE_PRIVATE:
if (!IS_ENABLED(CONFIG_DEVICE_PRIVATE)) {
WARN(1, "Device private memory not supported\n");
return ERR_PTR(-EINVAL);
}
if (!pgmap->ops || !pgmap->ops->migrate_to_ram) {
WARN(1, "Missing migrate_to_ram method\n");
return ERR_PTR(-EINVAL);
}
if (!pgmap->owner) {
WARN(1, "Missing owner\n");
return ERR_PTR(-EINVAL);
}
break;
case MEMORY_DEVICE_FS_DAX:
if (!IS_ENABLED(CONFIG_ZONE_DEVICE) ||
IS_ENABLED(CONFIG_FS_DAX_LIMITED)) {
WARN(1, "File system DAX not supported\n");
return ERR_PTR(-EINVAL);
}
break;
case MEMORY_DEVICE_DEVDAX:
case MEMORY_DEVICE_PCI_P2PDMA:
need_devmap_managed = false;
break;
default:
WARN(1, "Invalid pgmap type %d\n", pgmap->type);
break;
}
if (!pgmap->ref) {
if (pgmap->ops && (pgmap->ops->kill || pgmap->ops->cleanup))
return ERR_PTR(-EINVAL);
init_completion(&pgmap->done);
error = percpu_ref_init(&pgmap->internal_ref,
dev_pagemap_percpu_release, 0, GFP_KERNEL);
if (error)
return ERR_PTR(error);
pgmap->ref = &pgmap->internal_ref;
} else {
if (!pgmap->ops || !pgmap->ops->kill || !pgmap->ops->cleanup) {
WARN(1, "Missing reference count teardown definition\n");
return ERR_PTR(-EINVAL);
}
}
if (need_devmap_managed) {
error = devmap_managed_enable_get(pgmap);
if (error)
return ERR_PTR(error);
}
conflict_pgmap = get_dev_pagemap(PHYS_PFN(res->start), NULL);
if (conflict_pgmap) {
WARN(1, "Conflicting mapping in same section\n");
put_dev_pagemap(conflict_pgmap);
error = -ENOMEM;
goto err_array;
}
conflict_pgmap = get_dev_pagemap(PHYS_PFN(res->end), NULL);
if (conflict_pgmap) {
WARN(1, "Conflicting mapping in same section\n");
put_dev_pagemap(conflict_pgmap);
error = -ENOMEM;
goto err_array;
}
is_ram = region_intersects(res->start, resource_size(res),
IORESOURCE_SYSTEM_RAM, IORES_DESC_NONE);
if (is_ram != REGION_DISJOINT) {
WARN_ONCE(1, "%s attempted on %s region %pr\n", __func__,
is_ram == REGION_MIXED ? "mixed" : "ram", res);
error = -ENXIO;
goto err_array;
}
error = xa_err(xa_store_range(&pgmap_array, PHYS_PFN(res->start),
PHYS_PFN(res->end), pgmap, GFP_KERNEL));
if (error)
goto err_array;
if (nid < 0)
nid = numa_mem_id();
error = track_pfn_remap(NULL, &pgprot, PHYS_PFN(res->start), 0,
resource_size(res));
if (error)
goto err_pfn_remap;
mem_hotplug_begin();
/*
* For device private memory we call add_pages() as we only need to
* allocate and initialize struct page for the device memory. More-
* over the device memory is un-accessible thus we do not want to
* create a linear mapping for the memory like arch_add_memory()
* would do.
*
* For all other device memory types, which are accessible by
* the CPU, we do want the linear mapping and thus use
* arch_add_memory().
*/
if (pgmap->type == MEMORY_DEVICE_PRIVATE) {
error = add_pages(nid, PHYS_PFN(res->start),
PHYS_PFN(resource_size(res)), ¶ms);
} else {
error = kasan_add_zero_shadow(__va(res->start), resource_size(res));
if (error) {
mem_hotplug_done();
goto err_kasan;
}
error = arch_add_memory(nid, res->start, resource_size(res),
¶ms);
}
if (!error) {
struct zone *zone;
zone = &NODE_DATA(nid)->node_zones[ZONE_DEVICE];
move_pfn_range_to_zone(zone, PHYS_PFN(res->start),
PHYS_PFN(resource_size(res)), params.altmap);
}
mem_hotplug_done();
if (error)
goto err_add_memory;
/*
* Initialization of the pages has been deferred until now in order
* to allow us to do the work while not holding the hotplug lock.
*/
memmap_init_zone_device(&NODE_DATA(nid)->node_zones[ZONE_DEVICE],
PHYS_PFN(res->start),
PHYS_PFN(resource_size(res)), pgmap);
percpu_ref_get_many(pgmap->ref, pfn_end(pgmap) - pfn_first(pgmap));
return __va(res->start);
err_add_memory:
kasan_remove_zero_shadow(__va(res->start), resource_size(res));
err_kasan:
untrack_pfn(NULL, PHYS_PFN(res->start), resource_size(res));
err_pfn_remap:
pgmap_array_delete(res);
err_array:
dev_pagemap_kill(pgmap);
dev_pagemap_cleanup(pgmap);
devmap_managed_enable_put();
return ERR_PTR(error);
}
EXPORT_SYMBOL_GPL(memremap_pages);
/**
* devm_memremap_pages - remap and provide memmap backing for the given resource
* @dev: hosting device for @res
* @pgmap: pointer to a struct dev_pagemap
*
* Notes:
* 1/ At a minimum the res and type members of @pgmap must be initialized
* by the caller before passing it to this function
*
* 2/ The altmap field may optionally be initialized, in which case
* PGMAP_ALTMAP_VALID must be set in pgmap->flags.
*
* 3/ The ref field may optionally be provided, in which pgmap->ref must be
* 'live' on entry and will be killed and reaped at
* devm_memremap_pages_release() time, or if this routine fails.
*
* 4/ res is expected to be a host memory range that could feasibly be
* treated as a "System RAM" range, i.e. not a device mmio range, but
* this is not enforced.
*/
void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
{
int error;
void *ret;
ret = memremap_pages(pgmap, dev_to_node(dev));
if (IS_ERR(ret))
return ret;
error = devm_add_action_or_reset(dev, devm_memremap_pages_release,
pgmap);
if (error)
return ERR_PTR(error);
return ret;
}
EXPORT_SYMBOL_GPL(devm_memremap_pages);
void devm_memunmap_pages(struct device *dev, struct dev_pagemap *pgmap)
{
devm_release_action(dev, devm_memremap_pages_release, pgmap);
}
EXPORT_SYMBOL_GPL(devm_memunmap_pages);
unsigned long vmem_altmap_offset(struct vmem_altmap *altmap)
{
/* number of pfns from base where pfn_to_page() is valid */
if (altmap)
return altmap->reserve + altmap->free;
return 0;
}
void vmem_altmap_free(struct vmem_altmap *altmap, unsigned long nr_pfns)
{
altmap->alloc -= nr_pfns;
}
/**
* get_dev_pagemap() - take a new live reference on the dev_pagemap for @pfn
* @pfn: page frame number to lookup page_map
* @pgmap: optional known pgmap that already has a reference
*
* If @pgmap is non-NULL and covers @pfn it will be returned as-is. If @pgmap
* is non-NULL but does not cover @pfn the reference to it will be released.
*/
struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
struct dev_pagemap *pgmap)
{
resource_size_t phys = PFN_PHYS(pfn);
/*
* In the cached case we're already holding a live reference.
*/
if (pgmap) {
if (phys >= pgmap->res.start && phys <= pgmap->res.end)
return pgmap;
put_dev_pagemap(pgmap);
}
/* fall back to slow path lookup */
rcu_read_lock();
pgmap = xa_load(&pgmap_array, PHYS_PFN(phys));
if (pgmap && !percpu_ref_tryget_live(pgmap->ref))
pgmap = NULL;
rcu_read_unlock();
return pgmap;
}
EXPORT_SYMBOL_GPL(get_dev_pagemap);
#ifdef CONFIG_DEV_PAGEMAP_OPS
void free_devmap_managed_page(struct page *page)
{
/* notify page idle for dax */
if (!is_device_private_page(page)) {
wake_up_var(&page->_refcount);
return;
}
/* Clear Active bit in case of parallel mark_page_accessed */
__ClearPageActive(page);
__ClearPageWaiters(page);
mem_cgroup_uncharge(page);
/*
* When a device_private page is freed, the page->mapping field
* may still contain a (stale) mapping value. For example, the
* lower bits of page->mapping may still identify the page as an
* anonymous page. Ultimately, this entire field is just stale
* and wrong, and it will cause errors if not cleared. One
* example is:
*
* migrate_vma_pages()
* migrate_vma_insert_page()
* page_add_new_anon_rmap()
* __page_set_anon_rmap()
* ...checks page->mapping, via PageAnon(page) call,
* and incorrectly concludes that the page is an
* anonymous page. Therefore, it incorrectly,
* silently fails to set up the new anon rmap.
*
* For other types of ZONE_DEVICE pages, migration is either
* handled differently or not done at all, so there is no need
* to clear page->mapping.
*/
page->mapping = NULL;
page->pgmap->ops->page_free(page);
}
#endif /* CONFIG_DEV_PAGEMAP_OPS */