/* * Memory subsystem support * * Written by Matt Tolentino <matthew.e.tolentino@intel.com> * Dave Hansen <haveblue@us.ibm.com> * * This file provides the necessary infrastructure to represent * a SPARSEMEM-memory-model system's physical memory in /sysfs. * All arch-independent code that assumes MEMORY_HOTPLUG requires * SPARSEMEM should be contained here, or in mm/memory_hotplug.c. */ #include <linux/module.h>#include <linux/init.h>#include <linux/topology.h>#include <linux/capability.h>#include <linux/device.h>#include <linux/memory.h>#include <linux/memory_hotplug.h>#include <linux/mm.h>#include <linux/mutex.h>#include <linux/stat.h>#include <linux/slab.h> #include <linux/atomic.h>#include <asm/uaccess.h> static DEFINE_MUTEX(mem_sysfs_mutex); #define MEMORY_CLASS_NAME "memory" #define to_memory_block(dev) container_of(dev, struct memory_block, dev) static int sections_per_block; static inline int base_memory_block_id(int section_nr){ return section_nr / sections_per_block;} static int memory_subsys_online(struct device *dev);static int memory_subsys_offline(struct device *dev); static struct bus_type memory_subsys = { .name = MEMORY_CLASS_NAME, .dev_name = MEMORY_CLASS_NAME, .online = memory_subsys_online, .offline = memory_subsys_offline,}; static BLOCKING_NOTIFIER_HEAD(memory_chain); int register_memory_notifier(struct notifier_block *nb){ return blocking_notifier_chain_register(&memory_chain, nb);}EXPORT_SYMBOL(register_memory_notifier); void unregister_memory_notifier(struct notifier_block *nb){ blocking_notifier_chain_unregister(&memory_chain, nb);}EXPORT_SYMBOL(unregister_memory_notifier); static ATOMIC_NOTIFIER_HEAD(memory_isolate_chain); int register_memory_isolate_notifier(struct notifier_block *nb){ return atomic_notifier_chain_register(&memory_isolate_chain, nb);}EXPORT_SYMBOL(register_memory_isolate_notifier); void unregister_memory_isolate_notifier(struct notifier_block *nb){ atomic_notifier_chain_unregister(&memory_isolate_chain, nb);}EXPORT_SYMBOL(unregister_memory_isolate_notifier); static void memory_block_release(struct device *dev){ struct memory_block *mem = to_memory_block(dev); kfree(mem);} unsigned long __weak memory_block_size_bytes(void){ return MIN_MEMORY_BLOCK_SIZE;} static unsigned long get_memory_block_size(void){ unsigned long block_sz; block_sz = memory_block_size_bytes(); /* Validate blk_sz is a power of 2 and not less than section size */ if ((block_sz & (block_sz - 1)) || (block_sz < MIN_MEMORY_BLOCK_SIZE)) { WARN_ON(1); block_sz = MIN_MEMORY_BLOCK_SIZE; } return block_sz;} /* * use this as the physical section index that this memsection * uses. */ static ssize_t show_mem_start_phys_index(struct device *dev, struct device_attribute *attr, char *buf){ struct memory_block *mem = to_memory_block(dev); unsigned long phys_index; phys_index = mem->start_section_nr / sections_per_block; return sprintf(buf, "%08lx\n", phys_index);} /* * Show whether the section of memory is likely to be hot-removable */static ssize_t show_mem_removable(struct device *dev, struct device_attribute *attr, char *buf){ unsigned long i, pfn; int ret = 1; struct memory_block *mem = to_memory_block(dev); for (i = 0; i < sections_per_block; i++) { if (!present_section_nr(mem->start_section_nr + i)) continue; pfn = section_nr_to_pfn(mem->start_section_nr + i); ret &= is_mem_section_removable(pfn, PAGES_PER_SECTION); } return sprintf(buf, "%d\n", ret);} /* * online, offline, going offline, etc. */static ssize_t show_mem_state(struct device *dev, struct device_attribute *attr, char *buf){ struct memory_block *mem = to_memory_block(dev); ssize_t len = 0; /* * We can probably put these states in a nice little array * so that they're not open-coded */ switch (mem->state) { case MEM_ONLINE: len = sprintf(buf, "online\n"); break; case MEM_OFFLINE: len = sprintf(buf, "offline\n"); break; case MEM_GOING_OFFLINE: len = sprintf(buf, "going-offline\n"); break; default: len = sprintf(buf, "ERROR-UNKNOWN-%ld\n", mem->state); WARN_ON(1); break; } return len;} int memory_notify(unsigned long val, void *v){ return blocking_notifier_call_chain(&memory_chain, val, v);} int memory_isolate_notify(unsigned long val, void *v){ return atomic_notifier_call_chain(&memory_isolate_chain, val, v);} /* * The probe routines leave the pages reserved, just as the bootmem code does. * Make sure they're still that way. */static bool pages_correctly_reserved(unsigned long start_pfn){ int i, j; struct page *page; unsigned long pfn = start_pfn; /* * memmap between sections is not contiguous except with * SPARSEMEM_VMEMMAP. We lookup the page once per section * and assume memmap is contiguous within each section */ for (i = 0; i < sections_per_block; i++, pfn += PAGES_PER_SECTION) { if (WARN_ON_ONCE(!pfn_valid(pfn))) return false; page = pfn_to_page(pfn); for (j = 0; j < PAGES_PER_SECTION; j++) { if (PageReserved(page + j)) continue; printk(KERN_WARNING "section number %ld page number %d " "not reserved, was it already online?\n", pfn_to_section_nr(pfn), j); return false; } } return true;} /* * MEMORY_HOTPLUG depends on SPARSEMEM in mm/Kconfig, so it is * OK to have direct references to sparsemem variables in here. */static intmemory_block_action(unsigned long phys_index, unsigned long action, int online_type){ unsigned long start_pfn; unsigned long nr_pages = PAGES_PER_SECTION * sections_per_block; struct page *first_page; int ret; first_page = pfn_to_page(phys_index << PFN_SECTION_SHIFT); start_pfn = page_to_pfn(first_page); switch (action) { case MEM_ONLINE: if (!pages_correctly_reserved(start_pfn)) return -EBUSY; ret = online_pages(start_pfn, nr_pages, online_type); break; case MEM_OFFLINE: ret = offline_pages(start_pfn, nr_pages); break; default: WARN(1, KERN_WARNING "%s(%ld, %ld) unknown action: " "%ld\n", __func__, phys_index, action, action); ret = -EINVAL; } return ret;} static int memory_block_change_state(struct memory_block *mem, unsigned long to_state, unsigned long from_state_req){ int ret = 0; if (mem->state != from_state_req) return -EINVAL; if (to_state == MEM_OFFLINE) mem->state = MEM_GOING_OFFLINE; ret = memory_block_action(mem->start_section_nr, to_state, mem->online_type); mem->state = ret ? from_state_req : to_state; return ret;} /* The device lock serializes operations on memory_subsys_[online|offline] */static int memory_subsys_online(struct device *dev){ struct memory_block *mem = to_memory_block(dev); int ret; if (mem->state == MEM_ONLINE) return 0; /* * If we are called from store_mem_state(), online_type will be * set >= 0 Otherwise we were called from the device online * attribute and need to set the online_type. */ if (mem->online_type < 0) mem->online_type = ONLINE_KEEP; ret = memory_block_change_state(mem, MEM_ONLINE, MEM_OFFLINE); /* clear online_type */ mem->online_type = -1; return ret;} static int memory_subsys_offline(struct device *dev){ struct memory_block *mem = to_memory_block(dev); if (mem->state == MEM_OFFLINE) return 0; return memory_block_change_state(mem, MEM_OFFLINE, MEM_ONLINE);} static ssize_tstore_mem_state(struct device *dev, struct device_attribute *attr, const char *buf, size_t count){ struct memory_block *mem = to_memory_block(dev); int ret, online_type; ret = lock_device_hotplug_sysfs(); if (ret) return ret; if (!strncmp(buf, "online_kernel", min_t(int, count, 13))) online_type = ONLINE_KERNEL; else if (!strncmp(buf, "online_movable", min_t(int, count, 14))) online_type = ONLINE_MOVABLE; else if (!strncmp(buf, "online", min_t(int, count, 6))) online_type = ONLINE_KEEP; else if (!strncmp(buf, "offline", min_t(int, count, 7))) online_type = -1; else { ret = -EINVAL; goto err; } switch (online_type) { case ONLINE_KERNEL: case ONLINE_MOVABLE: case ONLINE_KEEP: /* * mem->online_type is not protected so there can be a * race here. However, when racing online, the first * will succeed and the second will just return as the * block will already be online. The online type * could be either one, but that is expected. */ mem->online_type = online_type; ret = device_online(&mem->dev); break; case -1: ret = device_offline(&mem->dev); break; default: ret = -EINVAL; /* should never happen */ } err: unlock_device_hotplug(); if (ret) return ret; return count;} /* * phys_device is a bad name for this. What I really want * is a way to differentiate between memory ranges that * are part of physical devices that constitute * a complete removable unit or fru. * i.e. do these ranges belong to the same physical device, * s.t. if I offline all of these sections I can then * remove the physical device? */static ssize_t show_phys_device(struct device *dev, struct device_attribute *attr, char *buf){ struct memory_block *mem = to_memory_block(dev); return sprintf(buf, "%d\n", mem->phys_device);} static DEVICE_ATTR(phys_index, 0444, show_mem_start_phys_index, NULL);static DEVICE_ATTR(state, 0644, show_mem_state, store_mem_state);static DEVICE_ATTR(phys_device, 0444, show_phys_device, NULL);static DEVICE_ATTR(removable, 0444, show_mem_removable, NULL); /* * Block size attribute stuff */static ssize_tprint_block_size(struct device *dev, struct device_attribute *attr, char *buf){ return sprintf(buf, "%lx\n", get_memory_block_size());} static DEVICE_ATTR(block_size_bytes, 0444, print_block_size, NULL); /* * Some architectures will have custom drivers to do this, and * will not need to do it from userspace. The fake hot-add code * as well as ppc64 will do all of their discovery in userspace * and will require this interface. */#ifdef CONFIG_ARCH_MEMORY_PROBEstatic ssize_tmemory_probe_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count){ u64 phys_addr; int nid; int i, ret; unsigned long pages_per_block = PAGES_PER_SECTION * sections_per_block; phys_addr = simple_strtoull(buf, NULL, 0); if (phys_addr & ((pages_per_block << PAGE_SHIFT) - 1)) return -EINVAL; for (i = 0; i < sections_per_block; i++) { nid = memory_add_physaddr_to_nid(phys_addr); ret = add_memory(nid, phys_addr, PAGES_PER_SECTION << PAGE_SHIFT); if (ret) goto out; phys_addr += MIN_MEMORY_BLOCK_SIZE; } ret = count;out: return ret;} static DEVICE_ATTR(probe, S_IWUSR, NULL, memory_probe_store);#endif #ifdef CONFIG_MEMORY_FAILURE/* * Support for offlining pages of memory */ /* Soft offline a page */static ssize_tstore_soft_offline_page(struct device *dev, struct device_attribute *attr, const char *buf, size_t count){ int ret; u64 pfn; if (!capable(CAP_SYS_ADMIN)) return -EPERM; if (kstrtoull(buf, 0, &pfn) < 0) return -EINVAL; pfn >>= PAGE_SHIFT; if (!pfn_valid(pfn)) return -ENXIO; ret = soft_offline_page(pfn_to_page(pfn), 0); return ret == 0 ? count : ret;} /* Forcibly offline a page, including killing processes. */static ssize_tstore_hard_offline_page(struct device *dev, struct device_attribute *attr, const char *buf, size_t count){ int ret; u64 pfn; if (!capable(CAP_SYS_ADMIN)) return -EPERM; if (kstrtoull(buf, 0, &pfn) < 0) return -EINVAL; pfn >>= PAGE_SHIFT; ret = memory_failure(pfn, 0, 0); return ret ? ret : count;} static DEVICE_ATTR(soft_offline_page, S_IWUSR, NULL, store_soft_offline_page);static DEVICE_ATTR(hard_offline_page, S_IWUSR, NULL, store_hard_offline_page);#endif /* * Note that phys_device is optional. It is here to allow for * differentiation between which *physical* devices each * section belongs to... */int __weak arch_get_memory_phys_device(unsigned long start_pfn){ return 0;} /* * A reference for the returned object is held and the reference for the * hinted object is released. */struct memory_block *find_memory_block_hinted(struct mem_section *section, struct memory_block *hint){ int block_id = base_memory_block_id(__section_nr(section)); struct device *hintdev = hint ? &hint->dev : NULL; struct device *dev; dev = subsys_find_device_by_id(&memory_subsys, block_id, hintdev); if (hint) put_device(&hint->dev);Lines 1–500 of 732. Load more
/* * Memory subsystem support * * Written by Matt Tolentino <matthew.e.tolentino@intel.com> * Dave Hansen <haveblue@us.ibm.com> * * This file provides the necessary infrastructure to represent * a SPARSEMEM-memory-model system's physical memory in /sysfs. * All arch-independent code that assumes MEMORY_HOTPLUG requires * SPARSEMEM should be contained here, or in mm/memory_hotplug.c. */ #include <linux/module.h> #include <linux/init.h> #include <linux/topology.h> #include <linux/capability.h> #include <linux/device.h> #include <linux/memory.h> #include <linux/memory_hotplug.h> #include <linux/mm.h> #include <linux/mutex.h> #include <linux/stat.h> #include <linux/slab.h> #include <linux/atomic.h> #include <asm/uaccess.h> static DEFINE_MUTEX(mem_sysfs_mutex); #define MEMORY_CLASS_NAME "memory" #define to_memory_block(dev) container_of(dev, struct memory_block, dev) static int sections_per_block; static inline int base_memory_block_id(int section_nr) { return section_nr / sections_per_block; } static int memory_subsys_online(struct device *dev); static int memory_subsys_offline(struct device *dev); static struct bus_type memory_subsys = { .name = MEMORY_CLASS_NAME, .dev_name = MEMORY_CLASS_NAME, .online = memory_subsys_online, .offline = memory_subsys_offline, }; static BLOCKING_NOTIFIER_HEAD(memory_chain); int register_memory_notifier(struct notifier_block *nb) { return blocking_notifier_chain_register(&memory_chain, nb); } EXPORT_SYMBOL(register_memory_notifier); void unregister_memory_notifier(struct notifier_block *nb) { blocking_notifier_chain_unregister(&memory_chain, nb); } EXPORT_SYMBOL(unregister_memory_notifier); static ATOMIC_NOTIFIER_HEAD(memory_isolate_chain); int register_memory_isolate_notifier(struct notifier_block *nb) { return atomic_notifier_chain_register(&memory_isolate_chain, nb); } EXPORT_SYMBOL(register_memory_isolate_notifier); void unregister_memory_isolate_notifier(struct notifier_block *nb) { atomic_notifier_chain_unregister(&memory_isolate_chain, nb); } EXPORT_SYMBOL(unregister_memory_isolate_notifier); static void memory_block_release(struct device *dev) { struct memory_block *mem = to_memory_block(dev); kfree(mem); } unsigned long __weak memory_block_size_bytes(void) { return MIN_MEMORY_BLOCK_SIZE; } static unsigned long get_memory_block_size(void) { unsigned long block_sz; block_sz = memory_block_size_bytes(); /* Validate blk_sz is a power of 2 and not less than section size */ if ((block_sz & (block_sz - 1)) || (block_sz < MIN_MEMORY_BLOCK_SIZE)) { WARN_ON(1); block_sz = MIN_MEMORY_BLOCK_SIZE; } return block_sz; } /* * use this as the physical section index that this memsection * uses. */ static ssize_t show_mem_start_phys_index(struct device *dev, struct device_attribute *attr, char *buf) { struct memory_block *mem = to_memory_block(dev); unsigned long phys_index; phys_index = mem->start_section_nr / sections_per_block; return sprintf(buf, "%08lx\n", phys_index); } /* * Show whether the section of memory is likely to be hot-removable */ static ssize_t show_mem_removable(struct device *dev, struct device_attribute *attr, char *buf) { unsigned long i, pfn; int ret = 1; struct memory_block *mem = to_memory_block(dev); for (i = 0; i < sections_per_block; i++) { if (!present_section_nr(mem->start_section_nr + i)) continue; pfn = section_nr_to_pfn(mem->start_section_nr + i); ret &= is_mem_section_removable(pfn, PAGES_PER_SECTION); } return sprintf(buf, "%d\n", ret); } /* * online, offline, going offline, etc. */ static ssize_t show_mem_state(struct device *dev, struct device_attribute *attr, char *buf) { struct memory_block *mem = to_memory_block(dev); ssize_t len = 0; /* * We can probably put these states in a nice little array * so that they're not open-coded */ switch (mem->state) { case MEM_ONLINE: len = sprintf(buf, "online\n"); break; case MEM_OFFLINE: len = sprintf(buf, "offline\n"); break; case MEM_GOING_OFFLINE: len = sprintf(buf, "going-offline\n"); break; default: len = sprintf(buf, "ERROR-UNKNOWN-%ld\n", mem->state); WARN_ON(1); break; } return len; } int memory_notify(unsigned long val, void *v) { return blocking_notifier_call_chain(&memory_chain, val, v); } int memory_isolate_notify(unsigned long val, void *v) { return atomic_notifier_call_chain(&memory_isolate_chain, val, v); } /* * The probe routines leave the pages reserved, just as the bootmem code does. * Make sure they're still that way. */ static bool pages_correctly_reserved(unsigned long start_pfn) { int i, j; struct page *page; unsigned long pfn = start_pfn; /* * memmap between sections is not contiguous except with * SPARSEMEM_VMEMMAP. We lookup the page once per section * and assume memmap is contiguous within each section */ for (i = 0; i < sections_per_block; i++, pfn += PAGES_PER_SECTION) { if (WARN_ON_ONCE(!pfn_valid(pfn))) return false; page = pfn_to_page(pfn); for (j = 0; j < PAGES_PER_SECTION; j++) { if (PageReserved(page + j)) continue; printk(KERN_WARNING "section number %ld page number %d " "not reserved, was it already online?\n", pfn_to_section_nr(pfn), j); return false; } } return true; } /* * MEMORY_HOTPLUG depends on SPARSEMEM in mm/Kconfig, so it is * OK to have direct references to sparsemem variables in here. */ static int memory_block_action(unsigned long phys_index, unsigned long action, int online_type) { unsigned long start_pfn; unsigned long nr_pages = PAGES_PER_SECTION * sections_per_block; struct page *first_page; int ret; first_page = pfn_to_page(phys_index << PFN_SECTION_SHIFT); start_pfn = page_to_pfn(first_page); switch (action) { case MEM_ONLINE: if (!pages_correctly_reserved(start_pfn)) return -EBUSY; ret = online_pages(start_pfn, nr_pages, online_type); break; case MEM_OFFLINE: ret = offline_pages(start_pfn, nr_pages); break; default: WARN(1, KERN_WARNING "%s(%ld, %ld) unknown action: " "%ld\n", __func__, phys_index, action, action); ret = -EINVAL; } return ret; } static int memory_block_change_state(struct memory_block *mem, unsigned long to_state, unsigned long from_state_req) { int ret = 0; if (mem->state != from_state_req) return -EINVAL; if (to_state == MEM_OFFLINE) mem->state = MEM_GOING_OFFLINE; ret = memory_block_action(mem->start_section_nr, to_state, mem->online_type); mem->state = ret ? from_state_req : to_state; return ret; } /* The device lock serializes operations on memory_subsys_[online|offline] */ static int memory_subsys_online(struct device *dev) { struct memory_block *mem = to_memory_block(dev); int ret; if (mem->state == MEM_ONLINE) return 0; /* * If we are called from store_mem_state(), online_type will be * set >= 0 Otherwise we were called from the device online * attribute and need to set the online_type. */ if (mem->online_type < 0) mem->online_type = ONLINE_KEEP; ret = memory_block_change_state(mem, MEM_ONLINE, MEM_OFFLINE); /* clear online_type */ mem->online_type = -1; return ret; } static int memory_subsys_offline(struct device *dev) { struct memory_block *mem = to_memory_block(dev); if (mem->state == MEM_OFFLINE) return 0; return memory_block_change_state(mem, MEM_OFFLINE, MEM_ONLINE); } static ssize_t store_mem_state(struct device *dev, struct device_attribute *attr, const char *buf, size_t count) { struct memory_block *mem = to_memory_block(dev); int ret, online_type; ret = lock_device_hotplug_sysfs(); if (ret) return ret; if (!strncmp(buf, "online_kernel", min_t(int, count, 13))) online_type = ONLINE_KERNEL; else if (!strncmp(buf, "online_movable", min_t(int, count, 14))) online_type = ONLINE_MOVABLE; else if (!strncmp(buf, "online", min_t(int, count, 6))) online_type = ONLINE_KEEP; else if (!strncmp(buf, "offline", min_t(int, count, 7))) online_type = -1; else { ret = -EINVAL; goto err; } switch (online_type) { case ONLINE_KERNEL: case ONLINE_MOVABLE: case ONLINE_KEEP: /* * mem->online_type is not protected so there can be a * race here. However, when racing online, the first * will succeed and the second will just return as the * block will already be online. The online type * could be either one, but that is expected. */ mem->online_type = online_type; ret = device_online(&mem->dev); break; case -1: ret = device_offline(&mem->dev); break; default: ret = -EINVAL; /* should never happen */ } err: unlock_device_hotplug(); if (ret) return ret; return count; } /* * phys_device is a bad name for this. What I really want * is a way to differentiate between memory ranges that * are part of physical devices that constitute * a complete removable unit or fru. * i.e. do these ranges belong to the same physical device, * s.t. if I offline all of these sections I can then * remove the physical device? */ static ssize_t show_phys_device(struct device *dev, struct device_attribute *attr, char *buf) { struct memory_block *mem = to_memory_block(dev); return sprintf(buf, "%d\n", mem->phys_device); } static DEVICE_ATTR(phys_index, 0444, show_mem_start_phys_index, NULL); static DEVICE_ATTR(state, 0644, show_mem_state, store_mem_state); static DEVICE_ATTR(phys_device, 0444, show_phys_device, NULL); static DEVICE_ATTR(removable, 0444, show_mem_removable, NULL); /* * Block size attribute stuff */ static ssize_t print_block_size(struct device *dev, struct device_attribute *attr, char *buf) { return sprintf(buf, "%lx\n", get_memory_block_size()); } static DEVICE_ATTR(block_size_bytes, 0444, print_block_size, NULL); /* * Some architectures will have custom drivers to do this, and * will not need to do it from userspace. The fake hot-add code * as well as ppc64 will do all of their discovery in userspace * and will require this interface. */ #ifdef CONFIG_ARCH_MEMORY_PROBE static ssize_t memory_probe_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count) { u64 phys_addr; int nid; int i, ret; unsigned long pages_per_block = PAGES_PER_SECTION * sections_per_block; phys_addr = simple_strtoull(buf, NULL, 0); if (phys_addr & ((pages_per_block << PAGE_SHIFT) - 1)) return -EINVAL; for (i = 0; i < sections_per_block; i++) { nid = memory_add_physaddr_to_nid(phys_addr); ret = add_memory(nid, phys_addr, PAGES_PER_SECTION << PAGE_SHIFT); if (ret) goto out; phys_addr += MIN_MEMORY_BLOCK_SIZE; } ret = count; out: return ret; } static DEVICE_ATTR(probe, S_IWUSR, NULL, memory_probe_store); #endif #ifdef CONFIG_MEMORY_FAILURE /* * Support for offlining pages of memory */ /* Soft offline a page */ static ssize_t store_soft_offline_page(struct device *dev, struct device_attribute *attr, const char *buf, size_t count) { int ret; u64 pfn; if (!capable(CAP_SYS_ADMIN)) return -EPERM; if (kstrtoull(buf, 0, &pfn) < 0) return -EINVAL; pfn >>= PAGE_SHIFT; if (!pfn_valid(pfn)) return -ENXIO; ret = soft_offline_page(pfn_to_page(pfn), 0); return ret == 0 ? count : ret; } /* Forcibly offline a page, including killing processes. */ static ssize_t store_hard_offline_page(struct device *dev, struct device_attribute *attr, const char *buf, size_t count) { int ret; u64 pfn; if (!capable(CAP_SYS_ADMIN)) return -EPERM; if (kstrtoull(buf, 0, &pfn) < 0) return -EINVAL; pfn >>= PAGE_SHIFT; ret = memory_failure(pfn, 0, 0); return ret ? ret : count; } static DEVICE_ATTR(soft_offline_page, S_IWUSR, NULL, store_soft_offline_page); static DEVICE_ATTR(hard_offline_page, S_IWUSR, NULL, store_hard_offline_page); #endif /* * Note that phys_device is optional. It is here to allow for * differentiation between which *physical* devices each * section belongs to... */ int __weak arch_get_memory_phys_device(unsigned long start_pfn) { return 0; } /* * A reference for the returned object is held and the reference for the * hinted object is released. */ struct memory_block *find_memory_block_hinted(struct mem_section *section, struct memory_block *hint) { int block_id = base_memory_block_id(__section_nr(section)); struct device *hintdev = hint ? &hint->dev : NULL; struct device *dev; dev = subsys_find_device_by_id(&memory_subsys, block_id, hintdev); if (hint) put_device(&hint->dev);