![Dan Williams](/assets/img/avatar_default.png)
Logan noticed that devm_memremap_pages_release() kills the percpu_ref
drops all the page references that were acquired at init and then
immediately proceeds to unplug, arch_remove_memory(), the backing pages
for the pagemap. If for some reason device shutdown actually collides
with a busy / elevated-ref-count page then arch_remove_memory() should
be deferred until after that reference is dropped.
As it stands the "wait for last page ref drop" happens *after*
devm_memremap_pages_release() returns, which is obviously too late and
can lead to crashes.
Fix this situation by assigning the responsibility to wait for the
percpu_ref to go idle to devm_memremap_pages() with a new ->cleanup()
callback. Implement the new cleanup callback for all
devm_memremap_pages() users: pmem, devdax, hmm, and p2pdma.
Link: http://lkml.kernel.org/r/155727339156.292046.5432007428235387859.stgit@dwillia2-desk3.amr.corp.intel.com
Fixes: 41e94a8513
("add devm_memremap_pages")
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reported-by: Logan Gunthorpe <logang@deltatee.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: "Jérôme Glisse" <jglisse@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
375 lines
10 KiB
C
375 lines
10 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/* Copyright(c) 2015 Intel Corporation. All rights reserved. */
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#include <linux/device.h>
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#include <linux/io.h>
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#include <linux/kasan.h>
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#include <linux/memory_hotplug.h>
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#include <linux/mm.h>
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#include <linux/pfn_t.h>
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#include <linux/swap.h>
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#include <linux/swapops.h>
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#include <linux/types.h>
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#include <linux/wait_bit.h>
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#include <linux/xarray.h>
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#include <linux/hmm.h>
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static DEFINE_XARRAY(pgmap_array);
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#define SECTION_MASK ~((1UL << PA_SECTION_SHIFT) - 1)
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#define SECTION_SIZE (1UL << PA_SECTION_SHIFT)
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#if IS_ENABLED(CONFIG_DEVICE_PRIVATE)
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vm_fault_t device_private_entry_fault(struct vm_area_struct *vma,
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unsigned long addr,
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swp_entry_t entry,
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unsigned int flags,
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pmd_t *pmdp)
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{
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struct page *page = device_private_entry_to_page(entry);
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struct hmm_devmem *devmem;
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devmem = container_of(page->pgmap, typeof(*devmem), pagemap);
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/*
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* The page_fault() callback must migrate page back to system memory
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* so that CPU can access it. This might fail for various reasons
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* (device issue, device was unsafely unplugged, ...). When such
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* error conditions happen, the callback must return VM_FAULT_SIGBUS.
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*
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* Note that because memory cgroup charges are accounted to the device
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* memory, this should never fail because of memory restrictions (but
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* allocation of regular system page might still fail because we are
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* out of memory).
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*
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* There is a more in-depth description of what that callback can and
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* cannot do, in include/linux/memremap.h
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*/
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return devmem->page_fault(vma, addr, page, flags, pmdp);
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}
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#endif /* CONFIG_DEVICE_PRIVATE */
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static void pgmap_array_delete(struct resource *res)
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{
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xa_store_range(&pgmap_array, PHYS_PFN(res->start), PHYS_PFN(res->end),
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NULL, GFP_KERNEL);
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synchronize_rcu();
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}
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static unsigned long pfn_first(struct dev_pagemap *pgmap)
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{
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const struct resource *res = &pgmap->res;
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struct vmem_altmap *altmap = &pgmap->altmap;
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unsigned long pfn;
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pfn = res->start >> PAGE_SHIFT;
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if (pgmap->altmap_valid)
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pfn += vmem_altmap_offset(altmap);
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return pfn;
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}
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static unsigned long pfn_end(struct dev_pagemap *pgmap)
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{
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const struct resource *res = &pgmap->res;
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return (res->start + resource_size(res)) >> PAGE_SHIFT;
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}
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static unsigned long pfn_next(unsigned long pfn)
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{
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if (pfn % 1024 == 0)
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cond_resched();
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return pfn + 1;
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}
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#define for_each_device_pfn(pfn, map) \
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for (pfn = pfn_first(map); pfn < pfn_end(map); pfn = pfn_next(pfn))
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static void devm_memremap_pages_release(void *data)
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{
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struct dev_pagemap *pgmap = data;
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struct device *dev = pgmap->dev;
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struct resource *res = &pgmap->res;
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resource_size_t align_start, align_size;
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unsigned long pfn;
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int nid;
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pgmap->kill(pgmap->ref);
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for_each_device_pfn(pfn, pgmap)
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put_page(pfn_to_page(pfn));
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pgmap->cleanup(pgmap->ref);
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/* pages are dead and unused, undo the arch mapping */
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align_start = res->start & ~(SECTION_SIZE - 1);
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align_size = ALIGN(res->start + resource_size(res), SECTION_SIZE)
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- align_start;
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nid = page_to_nid(pfn_to_page(align_start >> PAGE_SHIFT));
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mem_hotplug_begin();
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if (pgmap->type == MEMORY_DEVICE_PRIVATE) {
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pfn = align_start >> PAGE_SHIFT;
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__remove_pages(page_zone(pfn_to_page(pfn)), pfn,
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align_size >> PAGE_SHIFT, NULL);
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} else {
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arch_remove_memory(nid, align_start, align_size,
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pgmap->altmap_valid ? &pgmap->altmap : NULL);
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kasan_remove_zero_shadow(__va(align_start), align_size);
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}
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mem_hotplug_done();
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untrack_pfn(NULL, PHYS_PFN(align_start), align_size);
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pgmap_array_delete(res);
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dev_WARN_ONCE(dev, pgmap->altmap.alloc,
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"%s: failed to free all reserved pages\n", __func__);
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}
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/**
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* devm_memremap_pages - remap and provide memmap backing for the given resource
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* @dev: hosting device for @res
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* @pgmap: pointer to a struct dev_pagemap
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*
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* Notes:
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* 1/ At a minimum the res, ref and type members of @pgmap must be initialized
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* by the caller before passing it to this function
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*
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* 2/ The altmap field may optionally be initialized, in which case altmap_valid
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* must be set to true
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*
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* 3/ pgmap->ref must be 'live' on entry and will be killed and reaped
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* at devm_memremap_pages_release() time, or if this routine fails.
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*
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* 4/ res is expected to be a host memory range that could feasibly be
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* treated as a "System RAM" range, i.e. not a device mmio range, but
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* this is not enforced.
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*/
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void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
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{
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resource_size_t align_start, align_size, align_end;
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struct vmem_altmap *altmap = pgmap->altmap_valid ?
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&pgmap->altmap : NULL;
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struct resource *res = &pgmap->res;
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struct dev_pagemap *conflict_pgmap;
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struct mhp_restrictions restrictions = {
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/*
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* We do not want any optional features only our own memmap
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*/
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.altmap = altmap,
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};
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pgprot_t pgprot = PAGE_KERNEL;
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int error, nid, is_ram;
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if (!pgmap->ref || !pgmap->kill || !pgmap->cleanup) {
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WARN(1, "Missing reference count teardown definition\n");
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return ERR_PTR(-EINVAL);
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}
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align_start = res->start & ~(SECTION_SIZE - 1);
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align_size = ALIGN(res->start + resource_size(res), SECTION_SIZE)
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- align_start;
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align_end = align_start + align_size - 1;
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conflict_pgmap = get_dev_pagemap(PHYS_PFN(align_start), NULL);
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if (conflict_pgmap) {
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dev_WARN(dev, "Conflicting mapping in same section\n");
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put_dev_pagemap(conflict_pgmap);
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error = -ENOMEM;
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goto err_array;
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}
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conflict_pgmap = get_dev_pagemap(PHYS_PFN(align_end), NULL);
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if (conflict_pgmap) {
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dev_WARN(dev, "Conflicting mapping in same section\n");
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put_dev_pagemap(conflict_pgmap);
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error = -ENOMEM;
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goto err_array;
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}
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is_ram = region_intersects(align_start, align_size,
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IORESOURCE_SYSTEM_RAM, IORES_DESC_NONE);
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if (is_ram != REGION_DISJOINT) {
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WARN_ONCE(1, "%s attempted on %s region %pr\n", __func__,
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is_ram == REGION_MIXED ? "mixed" : "ram", res);
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error = -ENXIO;
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goto err_array;
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}
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pgmap->dev = dev;
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error = xa_err(xa_store_range(&pgmap_array, PHYS_PFN(res->start),
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PHYS_PFN(res->end), pgmap, GFP_KERNEL));
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if (error)
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goto err_array;
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nid = dev_to_node(dev);
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if (nid < 0)
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nid = numa_mem_id();
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error = track_pfn_remap(NULL, &pgprot, PHYS_PFN(align_start), 0,
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align_size);
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if (error)
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goto err_pfn_remap;
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mem_hotplug_begin();
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/*
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* For device private memory we call add_pages() as we only need to
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* allocate and initialize struct page for the device memory. More-
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* over the device memory is un-accessible thus we do not want to
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* create a linear mapping for the memory like arch_add_memory()
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* would do.
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*
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* For all other device memory types, which are accessible by
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* the CPU, we do want the linear mapping and thus use
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* arch_add_memory().
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*/
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if (pgmap->type == MEMORY_DEVICE_PRIVATE) {
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error = add_pages(nid, align_start >> PAGE_SHIFT,
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align_size >> PAGE_SHIFT, &restrictions);
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} else {
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error = kasan_add_zero_shadow(__va(align_start), align_size);
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if (error) {
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mem_hotplug_done();
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goto err_kasan;
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}
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error = arch_add_memory(nid, align_start, align_size,
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&restrictions);
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}
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if (!error) {
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struct zone *zone;
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zone = &NODE_DATA(nid)->node_zones[ZONE_DEVICE];
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move_pfn_range_to_zone(zone, align_start >> PAGE_SHIFT,
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align_size >> PAGE_SHIFT, altmap);
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}
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mem_hotplug_done();
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if (error)
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goto err_add_memory;
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/*
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* Initialization of the pages has been deferred until now in order
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* to allow us to do the work while not holding the hotplug lock.
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*/
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memmap_init_zone_device(&NODE_DATA(nid)->node_zones[ZONE_DEVICE],
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align_start >> PAGE_SHIFT,
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align_size >> PAGE_SHIFT, pgmap);
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percpu_ref_get_many(pgmap->ref, pfn_end(pgmap) - pfn_first(pgmap));
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error = devm_add_action_or_reset(dev, devm_memremap_pages_release,
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pgmap);
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if (error)
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return ERR_PTR(error);
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return __va(res->start);
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err_add_memory:
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kasan_remove_zero_shadow(__va(align_start), align_size);
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err_kasan:
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untrack_pfn(NULL, PHYS_PFN(align_start), align_size);
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err_pfn_remap:
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pgmap_array_delete(res);
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err_array:
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pgmap->kill(pgmap->ref);
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pgmap->cleanup(pgmap->ref);
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return ERR_PTR(error);
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}
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EXPORT_SYMBOL_GPL(devm_memremap_pages);
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void devm_memunmap_pages(struct device *dev, struct dev_pagemap *pgmap)
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{
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devm_release_action(dev, devm_memremap_pages_release, pgmap);
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}
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EXPORT_SYMBOL_GPL(devm_memunmap_pages);
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unsigned long vmem_altmap_offset(struct vmem_altmap *altmap)
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{
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/* number of pfns from base where pfn_to_page() is valid */
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return altmap->reserve + altmap->free;
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}
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void vmem_altmap_free(struct vmem_altmap *altmap, unsigned long nr_pfns)
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{
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altmap->alloc -= nr_pfns;
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}
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/**
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* get_dev_pagemap() - take a new live reference on the dev_pagemap for @pfn
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* @pfn: page frame number to lookup page_map
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* @pgmap: optional known pgmap that already has a reference
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*
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* If @pgmap is non-NULL and covers @pfn it will be returned as-is. If @pgmap
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* is non-NULL but does not cover @pfn the reference to it will be released.
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*/
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struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
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struct dev_pagemap *pgmap)
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{
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resource_size_t phys = PFN_PHYS(pfn);
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/*
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* In the cached case we're already holding a live reference.
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*/
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if (pgmap) {
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if (phys >= pgmap->res.start && phys <= pgmap->res.end)
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return pgmap;
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put_dev_pagemap(pgmap);
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}
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/* fall back to slow path lookup */
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rcu_read_lock();
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pgmap = xa_load(&pgmap_array, PHYS_PFN(phys));
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if (pgmap && !percpu_ref_tryget_live(pgmap->ref))
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pgmap = NULL;
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rcu_read_unlock();
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return pgmap;
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}
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EXPORT_SYMBOL_GPL(get_dev_pagemap);
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#ifdef CONFIG_DEV_PAGEMAP_OPS
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DEFINE_STATIC_KEY_FALSE(devmap_managed_key);
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EXPORT_SYMBOL(devmap_managed_key);
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static atomic_t devmap_enable;
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/*
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* Toggle the static key for ->page_free() callbacks when dev_pagemap
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* pages go idle.
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*/
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void dev_pagemap_get_ops(void)
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{
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if (atomic_inc_return(&devmap_enable) == 1)
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static_branch_enable(&devmap_managed_key);
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}
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EXPORT_SYMBOL_GPL(dev_pagemap_get_ops);
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void dev_pagemap_put_ops(void)
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{
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if (atomic_dec_and_test(&devmap_enable))
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static_branch_disable(&devmap_managed_key);
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}
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EXPORT_SYMBOL_GPL(dev_pagemap_put_ops);
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void __put_devmap_managed_page(struct page *page)
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{
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int count = page_ref_dec_return(page);
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/*
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* If refcount is 1 then page is freed and refcount is stable as nobody
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* holds a reference on the page.
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*/
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if (count == 1) {
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/* Clear Active bit in case of parallel mark_page_accessed */
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__ClearPageActive(page);
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__ClearPageWaiters(page);
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mem_cgroup_uncharge(page);
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page->pgmap->page_free(page, page->pgmap->data);
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} else if (!count)
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__put_page(page);
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}
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EXPORT_SYMBOL(__put_devmap_managed_page);
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#endif /* CONFIG_DEV_PAGEMAP_OPS */
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