The patch titled Subject: mm/sparsemem: pfn_to_page is not valid yet on SPARSEMEM has been added to the -mm tree. Its filename is mm-sparsemem-pfn_to_page-is-not-valid-yet-on-sparsemem.patch

This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/mm-sparsemem-pfn_to_page-is-not-val... and later at http://ozlabs.org/~akpm/mmotm/broken-out/mm-sparsemem-pfn_to_page-is-not-val...

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------------------------------------------------------ From: Wei Yang richardw.yang@linux.intel.com Subject: mm/sparsemem: pfn_to_page is not valid yet on SPARSEMEM

When we use SPARSEMEM instead of SPARSEMEM_VMEMMAP, pfn_to_page() doesn't work before sparse_init_one_section() is called. This leads to a crash when hotplug memory:

[ 41.839170] BUG: unable to handle page fault for address: 0000000006400000 [ 41.840663] #PF: supervisor write access in kernel mode [ 41.841822] #PF: error_code(0x0002) - not-present page [ 41.842970] PGD 0 P4D 0 [ 41.843538] Oops: 0002 [#1] SMP PTI [ 41.844125] CPU: 3 PID: 221 Comm: kworker/u16:1 Tainted: G W 5.5.0-next-20200205+ #343 [ 41.845659] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015 [ 41.846977] Workqueue: kacpi_hotplug acpi_hotplug_work_fn [ 41.847904] RIP: 0010:__memset+0x24/0x30 [ 41.848660] Code: cc cc cc cc cc cc 0f 1f 44 00 00 49 89 f9 48 89 d1 83 e2 07 48 c1 e9 03 40 0f b6 f6 48 b8 01 01 01 01 01 01 01 01 48 0f af c6 <f3> 48 ab 89 d1 f3 aa 4c 89 c8 c3 90 49 89 f9 40 88 f0 48 89 d1 f3 [ 41.851836] RSP: 0018:ffffb43ac0373c80 EFLAGS: 00010a87 [ 41.852686] RAX: ffffffffffffffff RBX: ffff8a1518800000 RCX: 0000000000050000 [ 41.853824] RDX: 0000000000000000 RSI: 00000000000000ff RDI: 0000000006400000 [ 41.854967] RBP: 0000000000140000 R08: 0000000000100000 R09: 0000000006400000 [ 41.856107] R10: 0000000000000000 R11: 0000000000000002 R12: 0000000000000000 [ 41.857255] R13: 0000000000000028 R14: 0000000000000000 R15: ffff8a153ffd9280 [ 41.858414] FS: 0000000000000000(0000) GS:ffff8a153ab00000(0000) knlGS:0000000000000000 [ 41.859703] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 41.860627] CR2: 0000000006400000 CR3: 0000000136fca000 CR4: 00000000000006e0 [ 41.861716] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 41.862680] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 41.863628] Call Trace: [ 41.863983] sparse_add_section+0x1c9/0x26a [ 41.864570] __add_pages+0xbf/0x150 [ 41.865057] add_pages+0x12/0x60 [ 41.865489] add_memory_resource+0xc8/0x210 [ 41.866017] ? wake_up_q+0xa0/0xa0 [ 41.866416] __add_memory+0x62/0xb0 [ 41.866825] acpi_memory_device_add+0x13f/0x300 [ 41.867410] acpi_bus_attach+0xf6/0x200 [ 41.867890] acpi_bus_scan+0x43/0x90 [ 41.868448] acpi_device_hotplug+0x275/0x3d0 [ 41.868972] acpi_hotplug_work_fn+0x1a/0x30 [ 41.869473] process_one_work+0x1a7/0x370 [ 41.869953] worker_thread+0x30/0x380 [ 41.870396] ? flush_rcu_work+0x30/0x30 [ 41.870846] kthread+0x112/0x130 [ 41.871236] ? kthread_create_on_node+0x60/0x60 [ 41.871770] ret_from_fork+0x35/0x40

We should use memmap as it did.

On x86 the impact is limited to x86_32 builds, or x86_64 configurations that override the default setting for SPARSEMEM_VMEMMAP.

[dan.j.williams@intel.com: changelog update] Link: http://lkml.kernel.org/r/20200219030454.4844-1-bhe@redhat.com Fixes: ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug") Signed-off-by: Wei Yang richardw.yang@linux.intel.com Signed-off-by: Baoquan He bhe@redhat.com Acked-by: David Hildenbrand david@redhat.com Reviewed-by: Baoquan He bhe@redhat.com Reviewed-by: Dan Williams dan.j.williams@intel.com Cc: Mike Rapoport rppt@linux.ibm.com Cc: Oscar Salvador osalvador@suse.de Cc: Michal Hocko mhocko@suse.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/sparse.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/sparse.c~mm-sparsemem-pfn_to_page-is-not-valid-yet-on-sparsemem +++ a/mm/sparse.c @@ -876,7 +876,7 @@ int __meminit sparse_add_section(int nid * Poison uninitialized struct pages in order to catch invalid flags * combinations. */ - page_init_poison(pfn_to_page(start_pfn), sizeof(struct page) * nr_pages); + page_init_poison(memmap, sizeof(struct page) * nr_pages);

ms = __nr_to_section(section_nr); set_section_nid(section_nr, nid); _

Patches currently in -mm which might be from richardw.yang@linux.intel.com are

mm-sparsemem-pfn_to_page-is-not-valid-yet-on-sparsemem.patch mm-sparsemem-get-address-to-page-struct-instead-of-address-to-pfn.patch mm-migratec-no-need-to-check-for-i-start-in-do_pages_move.patch mm-migratec-wrap-do_move_pages_to_node-and-store_status.patch mm-migratec-check-pagelist-in-move_pages_and_store_status.patch mm-migratec-unify-not-queued-for-migration-handling-in-do_pages_move.patch