mm/hmm/devmem: device memory hotplug using ZONE_DEVICE

This introduce a simple struct and associated helpers for device driver to
use when hotpluging un-addressable device memory as ZONE_DEVICE.  It will
find a unuse physical address range and trigger memory hotplug for it
which allocates and initialize struct page for the device memory.

Device driver should use this helper during device initialization to
hotplug the device memory.  It should only need to remove the memory once
the device is going offline (shutdown or hotremove).  There should not be
any userspace API to hotplug memory expect maybe for host device driver to
allow to add more memory to a guest device driver.

Device's memory is manage by the device driver and HMM only provides
helpers to that effect.

Link: http://lkml.kernel.org/r/20170817000548.32038-12-jglisse@redhat.com
Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Signed-off-by: Evgeny Baskakov <ebaskakov@nvidia.com>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Mark Hairgrove <mhairgrove@nvidia.com>
Signed-off-by: Sherry Cheung <SCheung@nvidia.com>
Signed-off-by: Subhash Gutti <sgutti@nvidia.com>
Signed-off-by: Balbir Singh <bsingharora@gmail.com>
Cc: Aneesh Kumar <aneesh.kumar@linux.vnet.ibm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Nellans <dnellans@nvidia.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Bob Liu <liubo95@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 378 insertions, 1 deletions

diff --git a/mm/hmm.c b/mm/hmm.c
index 3c6265d..afb5107 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -23,10 +23,16 @@
 #include <linux/swap.h>
 #include <linux/slab.h>
 #include <linux/sched.h>
+#include <linux/mmzone.h>
+#include <linux/pagemap.h>
 #include <linux/swapops.h>
 #include <linux/hugetlb.h>
+#include <linux/memremap.h>
 #include <linux/jump_label.h>
 #include <linux/mmu_notifier.h>
+#include <linux/memory_hotplug.h>
+
+#define PA_SECTION_SIZE (1UL << PA_SECTION_SHIFT)
 
 
 /*
@@ -426,7 +432,15 @@ again:
 			 * This is a special swap entry, ignore migration, use
 			 * device and report anything else as error.
 			 */
-			if (is_migration_entry(entry)) {
+			if (is_device_private_entry(entry)) {
+				pfns[i] = hmm_pfn_t_from_pfn(swp_offset(entry));
+				if (is_write_device_private_entry(entry)) {
+					pfns[i] |= HMM_PFN_WRITE;
+				} else if (write_fault)
+					goto fault;
+				pfns[i] |= HMM_PFN_DEVICE_UNADDRESSABLE;
+				pfns[i] |= flag;
+			} else if (is_migration_entry(entry)) {
 				if (hmm_vma_walk->fault) {
 					pte_unmap(ptep);
 					hmm_vma_walk->last = addr;
@@ -720,3 +734,366 @@ int hmm_vma_fault(struct vm_area_struct *vma,
 }
 EXPORT_SYMBOL(hmm_vma_fault);
 #endif /* IS_ENABLED(CONFIG_HMM_MIRROR) */
+
+
+#if IS_ENABLED(CONFIG_DEVICE_PRIVATE)
+struct page *hmm_vma_alloc_locked_page(struct vm_area_struct *vma,
+				       unsigned long addr)
+{
+	struct page *page;
+
+	page = alloc_page_vma(GFP_HIGHUSER, vma, addr);
+	if (!page)
+		return NULL;
+	lock_page(page);
+	return page;
+}
+EXPORT_SYMBOL(hmm_vma_alloc_locked_page);
+
+
+static void hmm_devmem_ref_release(struct percpu_ref *ref)
+{
+	struct hmm_devmem *devmem;
+
+	devmem = container_of(ref, struct hmm_devmem, ref);
+	complete(&devmem->completion);
+}
+
+static void hmm_devmem_ref_exit(void *data)
+{
+	struct percpu_ref *ref = data;
+	struct hmm_devmem *devmem;
+
+	devmem = container_of(ref, struct hmm_devmem, ref);
+	percpu_ref_exit(ref);
+	devm_remove_action(devmem->device, &hmm_devmem_ref_exit, data);
+}
+
+static void hmm_devmem_ref_kill(void *data)
+{
+	struct percpu_ref *ref = data;
+	struct hmm_devmem *devmem;
+
+	devmem = container_of(ref, struct hmm_devmem, ref);
+	percpu_ref_kill(ref);
+	wait_for_completion(&devmem->completion);
+	devm_remove_action(devmem->device, &hmm_devmem_ref_kill, data);
+}
+
+static int hmm_devmem_fault(struct vm_area_struct *vma,
+			    unsigned long addr,
+			    const struct page *page,
+			    unsigned int flags,
+			    pmd_t *pmdp)
+{
+	struct hmm_devmem *devmem = page->pgmap->data;
+
+	return devmem->ops->fault(devmem, vma, addr, page, flags, pmdp);
+}
+
+static void hmm_devmem_free(struct page *page, void *data)
+{
+	struct hmm_devmem *devmem = data;
+
+	devmem->ops->free(devmem, page);
+}
+
+static DEFINE_MUTEX(hmm_devmem_lock);
+static RADIX_TREE(hmm_devmem_radix, GFP_KERNEL);
+
+static void hmm_devmem_radix_release(struct resource *resource)
+{
+	resource_size_t key, align_start, align_size, align_end;
+
+	align_start = resource->start & ~(PA_SECTION_SIZE - 1);
+	align_size = ALIGN(resource_size(resource), PA_SECTION_SIZE);
+	align_end = align_start + align_size - 1;
+
+	mutex_lock(&hmm_devmem_lock);
+	for (key = resource->start;
+	     key <= resource->end;
+	     key += PA_SECTION_SIZE)
+		radix_tree_delete(&hmm_devmem_radix, key >> PA_SECTION_SHIFT);
+	mutex_unlock(&hmm_devmem_lock);
+}
+
+static void hmm_devmem_release(struct device *dev, void *data)
+{
+	struct hmm_devmem *devmem = data;
+	struct resource *resource = devmem->resource;
+	unsigned long start_pfn, npages;
+	struct zone *zone;
+	struct page *page;
+
+	if (percpu_ref_tryget_live(&devmem->ref)) {
+		dev_WARN(dev, "%s: page mapping is still live!\n", __func__);
+		percpu_ref_put(&devmem->ref);
+	}
+
+	/* pages are dead and unused, undo the arch mapping */
+	start_pfn = (resource->start & ~(PA_SECTION_SIZE - 1)) >> PAGE_SHIFT;
+	npages = ALIGN(resource_size(resource), PA_SECTION_SIZE) >> PAGE_SHIFT;
+
+	page = pfn_to_page(start_pfn);
+	zone = page_zone(page);
+
+	mem_hotplug_begin();
+	__remove_pages(zone, start_pfn, npages);
+	mem_hotplug_done();
+
+	hmm_devmem_radix_release(resource);
+}
+
+static struct hmm_devmem *hmm_devmem_find(resource_size_t phys)
+{
+	WARN_ON_ONCE(!rcu_read_lock_held());
+
+	return radix_tree_lookup(&hmm_devmem_radix, phys >> PA_SECTION_SHIFT);
+}
+
+static int hmm_devmem_pages_create(struct hmm_devmem *devmem)
+{
+	resource_size_t key, align_start, align_size, align_end;
+	struct device *device = devmem->device;
+	int ret, nid, is_ram;
+	unsigned long pfn;
+
+	align_start = devmem->resource->start & ~(PA_SECTION_SIZE - 1);
+	align_size = ALIGN(devmem->resource->start +
+			   resource_size(devmem->resource),
+			   PA_SECTION_SIZE) - align_start;
+
+	is_ram = region_intersects(align_start, align_size,
+				   IORESOURCE_SYSTEM_RAM,
+				   IORES_DESC_NONE);
+	if (is_ram == REGION_MIXED) {
+		WARN_ONCE(1, "%s attempted on mixed region %pr\n",
+				__func__, devmem->resource);
+		return -ENXIO;
+	}
+	if (is_ram == REGION_INTERSECTS)
+		return -ENXIO;
+
+	devmem->pagemap.type = MEMORY_DEVICE_PRIVATE;
+	devmem->pagemap.res = devmem->resource;
+	devmem->pagemap.page_fault = hmm_devmem_fault;
+	devmem->pagemap.page_free = hmm_devmem_free;
+	devmem->pagemap.dev = devmem->device;
+	devmem->pagemap.ref = &devmem->ref;
+	devmem->pagemap.data = devmem;
+
+	mutex_lock(&hmm_devmem_lock);
+	align_end = align_start + align_size - 1;
+	for (key = align_start; key <= align_end; key += PA_SECTION_SIZE) {
+		struct hmm_devmem *dup;
+
+		rcu_read_lock();
+		dup = hmm_devmem_find(key);
+		rcu_read_unlock();
+		if (dup) {
+			dev_err(device, "%s: collides with mapping for %s\n",
+				__func__, dev_name(dup->device));
+			mutex_unlock(&hmm_devmem_lock);
+			ret = -EBUSY;
+			goto error;
+		}
+		ret = radix_tree_insert(&hmm_devmem_radix,
+					key >> PA_SECTION_SHIFT,
+					devmem);
+		if (ret) {
+			dev_err(device, "%s: failed: %d\n", __func__, ret);
+			mutex_unlock(&hmm_devmem_lock);
+			goto error_radix;
+		}
+	}
+	mutex_unlock(&hmm_devmem_lock);
+
+	nid = dev_to_node(device);
+	if (nid < 0)
+		nid = numa_mem_id();
+
+	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.
+	 */
+	ret = add_pages(nid, align_start >> PAGE_SHIFT,
+			align_size >> PAGE_SHIFT, false);
+	if (ret) {
+		mem_hotplug_done();
+		goto error_add_memory;
+	}
+	move_pfn_range_to_zone(&NODE_DATA(nid)->node_zones[ZONE_DEVICE],
+				align_start >> PAGE_SHIFT,
+				align_size >> PAGE_SHIFT);
+	mem_hotplug_done();
+
+	for (pfn = devmem->pfn_first; pfn < devmem->pfn_last; pfn++) {
+		struct page *page = pfn_to_page(pfn);
+
+		page->pgmap = &devmem->pagemap;
+	}
+	return 0;
+
+error_add_memory:
+	untrack_pfn(NULL, PHYS_PFN(align_start), align_size);
+error_radix:
+	hmm_devmem_radix_release(devmem->resource);
+error:
+	return ret;
+}
+
+static int hmm_devmem_match(struct device *dev, void *data, void *match_data)
+{
+	struct hmm_devmem *devmem = data;
+
+	return devmem->resource == match_data;
+}
+
+static void hmm_devmem_pages_remove(struct hmm_devmem *devmem)
+{
+	devres_release(devmem->device, &hmm_devmem_release,
+		       &hmm_devmem_match, devmem->resource);
+}
+
+/*
+ * hmm_devmem_add() - hotplug ZONE_DEVICE memory for device memory
+ *
+ * @ops: memory event device driver callback (see struct hmm_devmem_ops)
+ * @device: device struct to bind the resource too
+ * @size: size in bytes of the device memory to add
+ * Returns: pointer to new hmm_devmem struct ERR_PTR otherwise
+ *
+ * This function first finds an empty range of physical address big enough to
+ * contain the new resource, and then hotplugs it as ZONE_DEVICE memory, which
+ * in turn allocates struct pages. It does not do anything beyond that; all
+ * events affecting the memory will go through the various callbacks provided
+ * by hmm_devmem_ops struct.
+ *
+ * Device driver should call this function during device initialization and
+ * is then responsible of memory management. HMM only provides helpers.
+ */
+struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops,
+				  struct device *device,
+				  unsigned long size)
+{
+	struct hmm_devmem *devmem;
+	resource_size_t addr;
+	int ret;
+
+	static_branch_enable(&device_private_key);
+
+	devmem = devres_alloc_node(&hmm_devmem_release, sizeof(*devmem),
+				   GFP_KERNEL, dev_to_node(device));
+	if (!devmem)
+		return ERR_PTR(-ENOMEM);
+
+	init_completion(&devmem->completion);
+	devmem->pfn_first = -1UL;
+	devmem->pfn_last = -1UL;
+	devmem->resource = NULL;
+	devmem->device = device;
+	devmem->ops = ops;
+
+	ret = percpu_ref_init(&devmem->ref, &hmm_devmem_ref_release,
+			      0, GFP_KERNEL);
+	if (ret)
+		goto error_percpu_ref;
+
+	ret = devm_add_action(device, hmm_devmem_ref_exit, &devmem->ref);
+	if (ret)
+		goto error_devm_add_action;
+
+	size = ALIGN(size, PA_SECTION_SIZE);
+	addr = min((unsigned long)iomem_resource.end,
+		   (1UL << MAX_PHYSMEM_BITS) - 1);
+	addr = addr - size + 1UL;
+
+	/*
+	 * FIXME add a new helper to quickly walk resource tree and find free
+	 * range
+	 *
+	 * FIXME what about ioport_resource resource ?
+	 */
+	for (; addr > size && addr >= iomem_resource.start; addr -= size) {
+		ret = region_intersects(addr, size, 0, IORES_DESC_NONE);
+		if (ret != REGION_DISJOINT)
+			continue;
+
+		devmem->resource = devm_request_mem_region(device, addr, size,
+							   dev_name(device));
+		if (!devmem->resource) {
+			ret = -ENOMEM;
+			goto error_no_resource;
+		}
+		break;
+	}
+	if (!devmem->resource) {
+		ret = -ERANGE;
+		goto error_no_resource;
+	}
+
+	devmem->resource->desc = IORES_DESC_DEVICE_PRIVATE_MEMORY;
+	devmem->pfn_first = devmem->resource->start >> PAGE_SHIFT;
+	devmem->pfn_last = devmem->pfn_first +
+			   (resource_size(devmem->resource) >> PAGE_SHIFT);
+
+	ret = hmm_devmem_pages_create(devmem);
+	if (ret)
+		goto error_pages;
+
+	devres_add(device, devmem);
+
+	ret = devm_add_action(device, hmm_devmem_ref_kill, &devmem->ref);
+	if (ret) {
+		hmm_devmem_remove(devmem);
+		return ERR_PTR(ret);
+	}
+
+	return devmem;
+
+error_pages:
+	devm_release_mem_region(device, devmem->resource->start,
+				resource_size(devmem->resource));
+error_no_resource:
+error_devm_add_action:
+	hmm_devmem_ref_kill(&devmem->ref);
+	hmm_devmem_ref_exit(&devmem->ref);
+error_percpu_ref:
+	devres_free(devmem);
+	return ERR_PTR(ret);
+}
+EXPORT_SYMBOL(hmm_devmem_add);
+
+/*
+ * hmm_devmem_remove() - remove device memory (kill and free ZONE_DEVICE)
+ *
+ * @devmem: hmm_devmem struct use to track and manage the ZONE_DEVICE memory
+ *
+ * This will hot-unplug memory that was hotplugged by hmm_devmem_add on behalf
+ * of the device driver. It will free struct page and remove the resource that
+ * reserved the physical address range for this device memory.
+ */
+void hmm_devmem_remove(struct hmm_devmem *devmem)
+{
+	resource_size_t start, size;
+	struct device *device;
+
+	if (!devmem)
+		return;
+
+	device = devmem->device;
+	start = devmem->resource->start;
+	size = resource_size(devmem->resource);
+
+	hmm_devmem_ref_kill(&devmem->ref);
+	hmm_devmem_ref_exit(&devmem->ref);
+	hmm_devmem_pages_remove(devmem);
+
+	devm_release_mem_region(device, start, size);
+}
+EXPORT_SYMBOL(hmm_devmem_remove);
+#endif /* IS_ENABLED(CONFIG_DEVICE_PRIVATE) */