mce: Uncorrected hardware memory error in user-access at af34214200
{1}[Hardware Error]: It has been corrected by h/w and requires no further action
mce: [Hardware Error]: Machine check events logged
{1}[Hardware Error]: event severity: corrected
Memory failure: 0xaf34214: reserved kernel page still referenced by 1 users
[..]
Memory failure: 0xaf34214: recovery action for reserved kernel page: Failed
mce: Memory error not recovered
In contrast to typical memory, dev_pagemap pages may be dax mapped. With
dax there is no possibility to map in another page dynamically since dax
establishes 1:1 physical address to file offset associations. Also
dev_pagemap pages associated with NVDIMM / persistent memory devices can
internal remap/repair addresses with poison. While memory_failure()
assumes that it can discard typical poisoned pages and keep them
unmapped indefinitely, dev_pagemap pages may be returned to service
after the error is cleared.
Teach memory_failure() to detect and handle MEMORY_DEVICE_HOST
dev_pagemap pages that have poison consumed by userspace. Mark the
memory as UC instead of unmapping it completely to allow ongoing access
via the device driver (nd_pmem). Later, nd_pmem will grow support for
marking the page back to WB when the error is cleared.
Cc: Jan Kara <jack@xxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Jérôme Glisse <jglisse@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Cc: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
include/linux/mm.h | 1
mm/memory-failure.c | 125 ++++++++++++++++++++++++++++++++++++++++++++++++++-
2 files changed, 124 insertions(+), 2 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index a0fbb9ffe380..374e5e9284f7 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2725,6 +2725,7 @@ enum mf_action_page_type {
MF_MSG_TRUNCATED_LRU,
MF_MSG_BUDDY,
MF_MSG_BUDDY_2ND,
+ MF_MSG_DAX,
MF_MSG_UNKNOWN,
};
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 8a81680d00dd..effaa7c7a1a4 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -55,6 +55,7 @@
#include <linux/hugetlb.h>
#include <linux/memory_hotplug.h>
#include <linux/mm_inline.h>
+#include <linux/memremap.h>
#include <linux/kfifo.h>
#include <linux/ratelimit.h>
#include "internal.h"
@@ -263,6 +264,40 @@ void shake_page(struct page *p, int access)
}
EXPORT_SYMBOL_GPL(shake_page);
+static unsigned long dev_pagemap_mapping_size(struct page *page,
+ struct vm_area_struct *vma)
+{
+ unsigned long address = vma_address(page, vma);
+ pgd_t *pgd;
+ p4d_t *p4d;
+ pud_t *pud;
+ pmd_t *pmd;
+ pte_t *pte;
+
+ pgd = pgd_offset(vma->vm_mm, address);
+ if (!pgd_present(*pgd))
+ return 0;
+ p4d = p4d_offset(pgd, address);
+ if (!p4d_present(*p4d))
+ return 0;
+ pud = pud_offset(p4d, address);
+ if (!pud_present(*pud))
+ return 0;
+ if (pud_devmap(*pud))
+ return PUD_SIZE;
+ pmd = pmd_offset(pud, address);
+ if (!pmd_present(*pmd))
+ return 0;
+ if (pmd_devmap(*pmd))
+ return PMD_SIZE;
+ pte = pte_offset_map(pmd, address);
+ if (!pte_present(*pte))
+ return 0;
+ if (pte_devmap(*pte))
+ return PAGE_SIZE;
+ return 0;
+}
+
/*
* Failure handling: if we can't find or can't kill a process there's
* not much we can do. We just print a message and ignore otherwise.
@@ -292,7 +327,10 @@ static void add_to_kill(struct task_struct *tsk, struct page *p,
}
tk->addr = page_address_in_vma(p, vma);
tk->addr_valid = 1;
- tk->size_shift = compound_order(compound_head(p)) + PAGE_SHIFT;
+ if (is_zone_device_page(p))
+ tk->size_shift = ilog2(dev_pagemap_mapping_size(p, vma));
+ else
+ tk->size_shift = compound_order(compound_head(p)) + PAGE_SHIFT;
/*
* In theory we don't have to kill when the page was
@@ -300,7 +338,7 @@ static void add_to_kill(struct task_struct *tsk, struct page *p,
* likely very rare kill anyways just out of paranoia, but use
* a SIGKILL because the error is not contained anymore.
*/
- if (tk->addr == -EFAULT) {
+ if (tk->addr == -EFAULT || tk->size_shift == 0) {
pr_info("Memory failure: Unable to find user space address %lx in %s\n",
page_to_pfn(p), tsk->comm);
tk->addr_valid = 0;
@@ -514,6 +552,7 @@ static const char * const action_page_types[] = {
[MF_MSG_TRUNCATED_LRU] = "already truncated LRU page",
[MF_MSG_BUDDY] = "free buddy page",
[MF_MSG_BUDDY_2ND] = "free buddy page (2nd try)",
+ [MF_MSG_DAX] = "dax page",
[MF_MSG_UNKNOWN] = "unknown page",
};
@@ -1111,6 +1150,83 @@ static int memory_failure_hugetlb(unsigned long pfn, int flags)
return res;
}
+static int memory_failure_dev_pagemap(unsigned long pfn, int flags,
+ struct dev_pagemap *pgmap)
+{
+ struct page *page = pfn_to_page(pfn);
+ const bool unmap_success = true;
+ unsigned long size = 0;
+ struct to_kill *tk;
+ LIST_HEAD(tokill);
+ int rc = -EBUSY;
+ loff_t start;
+
+ /*
+ * Prevent the inode from being freed while we are interrogating
+ * the address_space, typically this would be handled by
+ * lock_page(), but dax pages do not use the page lock. This
+ * also prevents changes to the mapping of this pfn until
+ * poison signaling is complete.
+ */
+ if (!dax_lock_mapping_entry(page))
+ goto out;
+
+ if (hwpoison_filter(page)) {
+ rc = 0;
+ goto unlock;
+ }
+
+ switch (pgmap->type) {
+ case MEMORY_DEVICE_PRIVATE:
+ case MEMORY_DEVICE_PUBLIC:
+ /*
+ * TODO: Handle HMM pages which may need coordination
+ * with device-side memory.
+ */
+ goto unlock;
+ default:
+ break;
+ }
+
+ /*
+ * Use this flag as an indication that the dax page has been
+ * remapped UC to prevent speculative consumption of poison.
+ */
+ SetPageHWPoison(page);
+
+ /*
+ * Unlike System-RAM there is no possibility to swap in a
+ * different physical page at a given virtual address, so all
+ * userspace consumption of ZONE_DEVICE memory necessitates
+ * SIGBUS (i.e. MF_MUST_KILL)
+ */
+ flags |= MF_ACTION_REQUIRED | MF_MUST_KILL;
+ collect_procs(page, &tokill, flags & MF_ACTION_REQUIRED);
+
+ list_for_each_entry(tk, &tokill, nd)
+ if (tk->size_shift)
+ size = max(size, 1UL << tk->size_shift);
+ if (size) {
+ /*
+ * Unmap the largest mapping to avoid breaking up
+ * device-dax mappings which are constant size. The
+ * actual size of the mapping being torn down is
+ * communicated in siginfo, see kill_proc()
+ */
+ start = (page->index << PAGE_SHIFT) & ~(size - 1);
+ unmap_mapping_range(page->mapping, start, start + size, 0);
+ }
+ kill_procs(&tokill, flags & MF_MUST_KILL, !unmap_success, pfn, flags);
+ rc = 0;
+unlock:
+ dax_unlock_mapping_entry(page);
+out:
+ /* drop pgmap ref acquired in caller */
+ put_dev_pagemap(pgmap);
+ action_result(pfn, MF_MSG_DAX, rc ? MF_FAILED : MF_RECOVERED);
+ return rc;
+}
+
/**
* memory_failure - Handle memory failure of a page.
* @pfn: Page Number of the corrupted page
@@ -1133,6 +1249,7 @@ int memory_failure(unsigned long pfn, int flags)
struct page *p;
struct page *hpage;
struct page *orig_head;
+ struct dev_pagemap *pgmap;
int res;
unsigned long page_flags;
@@ -1145,6 +1262,10 @@ int memory_failure(unsigned long pfn, int flags)
return -ENXIO;
}
+ pgmap = get_dev_pagemap(pfn, NULL);
+ if (pgmap)
+ return memory_failure_dev_pagemap(pfn, flags, pgmap);
+
p = pfn_to_page(pfn);
if (PageHuge(p))
return memory_failure_hugetlb(pfn, flags);
