From 2ec41967189cd65a8f79c760dd1b50c4f56e8ac6 Mon Sep 17 00:00:00 2001 From: Ankit Agrawal Date: Sun, 2 Nov 2025 18:44:33 +0000 Subject: [PATCH] mm: handle poisoning of pfn without struct pages MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Poison (or ECC) errors can be very common on a large size cluster. The kernel MM currently does not handle ECC errors / poison on a memory region that is not backed by struct pages. If a memory region mapped using remap_pfn_range() for example, but not added to the kernel, MM will not have associated struct pages. Add a new mechanism to handle memory failure on such memory. Make kernel MM expose a function to allow modules managing the device memory to register the device memory SPA and the address space associated it. MM maintains this information as an interval tree. On poison, MM can search for the range that the poisoned PFN belong and use the address_space to determine the mapping VMA. In this implementation, kernel MM follows the following sequence that is largely similar to the memory_failure() handler for struct page backed memory: 1. memory_failure() is triggered on reception of a poison error. An absence of struct page is detected and consequently memory_failure_pfn() is executed. 2. memory_failure_pfn() collects the processes mapped to the PFN. 3. memory_failure_pfn() sends SIGBUS to all the processes mapping the faulty PFN using kill_procs(). Note that there is one primary difference versus the handling of the poison on struct pages, which is to skip unmapping to the faulty PFN. This is done to handle the huge PFNMAP support added recently [1] that enables VM_PFNMAP vmas to map at PMD or PUD level. A poison to a PFN mapped in such as way would need breaking the PMD/PUD mapping into PTEs that will get mirrored into the S2. This can greatly increase the cost of table walks and have a major performance impact. Link: https://lore.kernel.org/all/20240826204353.2228736-1-peterx@redhat.com/ [1] Link: https://lkml.kernel.org/r/20251102184434.2406-3-ankita@nvidia.com Signed-off-by: Ankit Agrawal Cc: Aniket Agashe Cc: Borislav Betkov Cc: David Hildenbrand Cc: Hanjun Guo Cc: Ira Weiny Cc: Jason Gunthorpe Cc: Joanthan Cameron Cc: Kevin Tian Cc: Kirti Wankhede Cc: Len Brown Cc: Liam Howlett Cc: Lorenzo Stoakes Cc: "Luck, Tony" Cc: Matthew R. Ochs Cc: Mauro Carvalho Chehab Cc: Miaohe Lin Cc: Michal Hocko Cc: Mike Rapoport Cc: Naoya Horiguchi Cc: Neo Jia Cc: Peter Zijlstra Cc: Shuai Xue Cc: Smita Koralahalli Channabasappa Cc: Suren Baghdasaryan Cc: Tarun Gupta Cc: Uwe Kleine-König Cc: Vikram Sethi Cc: Vlastimil Babka Cc: Zhi Wang Signed-off-by: Andrew Morton --- MAINTAINERS | 1 + include/linux/memory-failure.h | 17 ++++ include/linux/mm.h | 1 + include/ras/ras_event.h | 1 + mm/Kconfig | 1 + mm/memory-failure.c | 145 ++++++++++++++++++++++++++++++++- 6 files changed, 165 insertions(+), 1 deletion(-) create mode 100644 include/linux/memory-failure.h diff --git a/MAINTAINERS b/MAINTAINERS index 2625bc3d53d8..5cf6873569d3 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -11557,6 +11557,7 @@ M: Miaohe Lin R: Naoya Horiguchi L: linux-mm@kvack.org S: Maintained +F: include/linux/memory-failure.h F: mm/hwpoison-inject.c F: mm/memory-failure.c diff --git a/include/linux/memory-failure.h b/include/linux/memory-failure.h new file mode 100644 index 000000000000..bc326503d2d2 --- /dev/null +++ b/include/linux/memory-failure.h @@ -0,0 +1,17 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _LINUX_MEMORY_FAILURE_H +#define _LINUX_MEMORY_FAILURE_H + +#include + +struct pfn_address_space; + +struct pfn_address_space { + struct interval_tree_node node; + struct address_space *mapping; +}; + +int register_pfn_address_space(struct pfn_address_space *pfn_space); +void unregister_pfn_address_space(struct pfn_address_space *pfn_space); + +#endif /* _LINUX_MEMORY_FAILURE_H */ diff --git a/include/linux/mm.h b/include/linux/mm.h index 7bcd9e6fbc3c..b636d12bb651 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -4285,6 +4285,7 @@ enum mf_action_page_type { MF_MSG_DAX, MF_MSG_UNSPLIT_THP, MF_MSG_ALREADY_POISONED, + MF_MSG_PFN_MAP, MF_MSG_UNKNOWN, }; diff --git a/include/ras/ras_event.h b/include/ras/ras_event.h index c8cd0f00c845..fecfeb7c8be7 100644 --- a/include/ras/ras_event.h +++ b/include/ras/ras_event.h @@ -375,6 +375,7 @@ TRACE_EVENT(aer_event, EM ( MF_MSG_DAX, "dax page" ) \ EM ( MF_MSG_UNSPLIT_THP, "unsplit thp" ) \ EM ( MF_MSG_ALREADY_POISONED, "already poisoned" ) \ + EM ( MF_MSG_PFN_MAP, "non struct page pfn" ) \ EMe ( MF_MSG_UNKNOWN, "unknown page" ) /* diff --git a/mm/Kconfig b/mm/Kconfig index eae03b14f7de..d548976d0e0a 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -741,6 +741,7 @@ config MEMORY_FAILURE depends on ARCH_SUPPORTS_MEMORY_FAILURE bool "Enable recovery from hardware memory errors" select RAS + select INTERVAL_TREE help Enables code to recover from some memory failures on systems with MCA recovery. This allows a system to continue running diff --git a/mm/memory-failure.c b/mm/memory-failure.c index 560884dd6250..77391b6f9f76 100644 --- a/mm/memory-failure.c +++ b/mm/memory-failure.c @@ -38,6 +38,7 @@ #include #include +#include #include #include #include @@ -154,6 +155,10 @@ static const struct ctl_table memory_failure_table[] = { } }; +static struct rb_root_cached pfn_space_itree = RB_ROOT_CACHED; + +static DEFINE_MUTEX(pfn_space_lock); + /* * Return values: * 1: the page is dissolved (if needed) and taken off from buddy, @@ -885,6 +890,7 @@ static const char * const action_page_types[] = { [MF_MSG_DAX] = "dax page", [MF_MSG_UNSPLIT_THP] = "unsplit thp", [MF_MSG_ALREADY_POISONED] = "already poisoned page", + [MF_MSG_PFN_MAP] = "non struct page pfn", [MF_MSG_UNKNOWN] = "unknown page", }; @@ -1277,7 +1283,7 @@ static int action_result(unsigned long pfn, enum mf_action_page_type type, { trace_memory_failure_event(pfn, type, result); - if (type != MF_MSG_ALREADY_POISONED) { + if (type != MF_MSG_ALREADY_POISONED && type != MF_MSG_PFN_MAP) { num_poisoned_pages_inc(pfn); update_per_node_mf_stats(pfn, result); } @@ -2147,6 +2153,135 @@ static void kill_procs_now(struct page *p, unsigned long pfn, int flags, kill_procs(&tokill, true, pfn, flags); } +int register_pfn_address_space(struct pfn_address_space *pfn_space) +{ + guard(mutex)(&pfn_space_lock); + + if (interval_tree_iter_first(&pfn_space_itree, + pfn_space->node.start, + pfn_space->node.last)) + return -EBUSY; + + interval_tree_insert(&pfn_space->node, &pfn_space_itree); + + return 0; +} +EXPORT_SYMBOL_GPL(register_pfn_address_space); + +void unregister_pfn_address_space(struct pfn_address_space *pfn_space) +{ + guard(mutex)(&pfn_space_lock); + + if (interval_tree_iter_first(&pfn_space_itree, + pfn_space->node.start, + pfn_space->node.last)) + interval_tree_remove(&pfn_space->node, &pfn_space_itree); +} +EXPORT_SYMBOL_GPL(unregister_pfn_address_space); + +static void add_to_kill_pfn(struct task_struct *tsk, + struct vm_area_struct *vma, + struct list_head *to_kill, + unsigned long pfn) +{ + struct to_kill *tk; + + tk = kmalloc(sizeof(*tk), GFP_ATOMIC); + if (!tk) { + pr_info("Unable to kill proc %d\n", tsk->pid); + return; + } + + /* Check for pgoff not backed by struct page */ + tk->addr = vma_address(vma, pfn, 1); + tk->size_shift = PAGE_SHIFT; + + if (tk->addr == -EFAULT) + pr_info("Unable to find address %lx in %s\n", + pfn, tsk->comm); + + get_task_struct(tsk); + tk->tsk = tsk; + list_add_tail(&tk->nd, to_kill); +} + +/* + * Collect processes when the error hit a PFN not backed by struct page. + */ +static void collect_procs_pfn(struct address_space *mapping, + unsigned long pfn, struct list_head *to_kill) +{ + struct vm_area_struct *vma; + struct task_struct *tsk; + + i_mmap_lock_read(mapping); + rcu_read_lock(); + for_each_process(tsk) { + struct task_struct *t = tsk; + + t = task_early_kill(tsk, true); + if (!t) + continue; + vma_interval_tree_foreach(vma, &mapping->i_mmap, pfn, pfn) { + if (vma->vm_mm == t->mm) + add_to_kill_pfn(t, vma, to_kill, pfn); + } + } + rcu_read_unlock(); + i_mmap_unlock_read(mapping); +} + +/** + * memory_failure_pfn - Handle memory failure on a page not backed by + * struct page. + * @pfn: Page Number of the corrupted page + * @flags: fine tune action taken + * + * Return: + * 0 - success, + * -EBUSY - Page PFN does not belong to any address space mapping. + */ +static int memory_failure_pfn(unsigned long pfn, int flags) +{ + struct interval_tree_node *node; + LIST_HEAD(tokill); + + scoped_guard(mutex, &pfn_space_lock) { + bool mf_handled = false; + + /* + * Modules registers with MM the address space mapping to + * the device memory they manage. Iterate to identify + * exactly which address space has mapped to this failing + * PFN. + */ + for (node = interval_tree_iter_first(&pfn_space_itree, pfn, pfn); node; + node = interval_tree_iter_next(node, pfn, pfn)) { + struct pfn_address_space *pfn_space = + container_of(node, struct pfn_address_space, node); + + collect_procs_pfn(pfn_space->mapping, pfn, &tokill); + + mf_handled = true; + } + + if (!mf_handled) + return action_result(pfn, MF_MSG_PFN_MAP, MF_IGNORED); + } + + /* + * Unlike System-RAM there is no possibility to swap in a different + * physical page at a given virtual address, so all userspace + * consumption of direct PFN memory necessitates SIGBUS (i.e. + * MF_MUST_KILL) + */ + flags |= MF_ACTION_REQUIRED | MF_MUST_KILL; + + kill_procs(&tokill, true, pfn, flags); + + return action_result(pfn, MF_MSG_PFN_MAP, MF_RECOVERED); +} + /** * memory_failure - Handle memory failure of a page. * @pfn: Page Number of the corrupted page @@ -2196,6 +2331,14 @@ int memory_failure(unsigned long pfn, int flags) if (res == 0) goto unlock_mutex; + if (!pfn_valid(pfn) && !arch_is_platform_page(PFN_PHYS(pfn))) { + /* + * The PFN is not backed by struct page. + */ + res = memory_failure_pfn(pfn, flags); + goto unlock_mutex; + } + if (pfn_valid(pfn)) { pgmap = get_dev_pagemap(pfn); put_ref_page(pfn, flags);