sparse_init_nid() is careful to leave alone every section whose vmemmap
has already been set up by sparse_vmemmap_init_nid_early(); it only clears
section_mem_map for the rest:
if (!preinited_vmemmap_section(ms))
ms->section_mem_map = 0;
A leftover line after that conditional block
ms->section_mem_map = 0;
was supposed to be deleted but was missed in the failure path, causing the
field to be overwritten for all sections when memory allocation fails,
effectively destroying the pre-initialization check.
Drop the stray assignment so that preinited sections retain their
already valid state.
Those pre-inited sections (HugeTLB pages) are not activated. However,
such failures are extremely rare, so I don't see any major userspace
issues.
Link: https://lore.kernel.org/20260331113724.2080833-1-songmuchun@bytedance.com
Fixes: d65917c423 ("mm/sparse: allow for alternate vmemmap section init at boot")
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed by: Donet Tom <donettom@linux.ibm.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Frank van der Linden <fvdl@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
In 2008, we added through commit 48c906823f ("memory hotplug: allocate
usemap on the section with pgdat") quite some complexity to try allocating
memory for the "usemap" (storing pageblock information per memory section)
for a memory section close to the memory of the "pgdat" of the node.
The goal was to make memory hotunplug of boot memory more likely to
succeed. That commit also added some checks for circular dependencies
between two memory sections, whereby two memory sections would contain
each others usemap, turning both boot memory sections un-removable.
However, in 2010, commit a4322e1bad ("sparsemem: Put usemap for one node
together") started allocating the usemap for multiple memory sections on
the same node in one chunk, effectively grouping all usemap allocations of
the same node in a single memblock allocation.
We don't really give guarantees about memory hotunplug of boot memory, and
with the change in 2010, it is impossible in practice to get any circular
dependencies.
So let's simply remove this complexity.
Link: https://lkml.kernel.org/r/20260320-sparsemem_cleanups-v2-10-096addc8800d@kernel.org
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Wei Xu <weixugc@google.com>
Cc: Yuanchu Xie <yuanchu@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
MEM_PREPARE_ONLINE/MEM_FINISH_OFFLINE memory notifiers were introduced
to prepare the transition of memory to and from a physically accessible
state. This enhancement was crucial for implementing the "memmap on memory"
feature for s390.
With introduction of dynamic (de)configuration of hotpluggable memory,
memory can be brought to accessible state before add_memory(). Memory
can be brought to inaccessible state before remove_memory(). Hence,
there is no need of MEM_PREPARE_ONLINE/MEM_FINISH_OFFLINE memory
notifiers anymore.
This basically reverts commit
c5f1e2d189 ("mm/memory_hotplug: introduce MEM_PREPARE_ONLINE/MEM_FINISH_OFFLINE notifiers")
Additionally, apply minor adjustments to the function parameters of
move_pfn_range_to_zone() and mhp_supports_memmap_on_memory() to ensure
compatibility with the latest branch.
Acked-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
For !CONFIG_SPARSEMEM_VMEMMAP, memmap page accounting is currently done
upfront in sparse_buffer_init(). However, sparse_buffer_alloc() may
return NULL in failure scenario.
Also, memmap pages may be allocated either from the memblock allocator
during early boot or from the buddy allocator. When removed via
arch_remove_memory(), accounting of memmap pages must reflect the original
allocation source.
To ensure correctness:
* Account memmap pages after successful allocation in sparse_init_nid()
and section_activate().
* Account memmap pages in section_deactivate() based on allocation
source.
Link: https://lkml.kernel.org/r/20250807183545.1424509-1-sumanthk@linux.ibm.com
Fixes: 15995a3524 ("mm: report per-page metadata information")
Signed-off-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
Suggested-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Wei Yang <richard.weiyang@gmail.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Add functions that are called just before the per-section memmap is
initialized and just before the memmap page structures are initialized.
They are called sparse_vmemmap_init_nid_early and
sparse_vmemmap_init_nid_late, respectively.
This allows for mm subsystems to add calls to initialize memmap and page
structures in a specific way, if using SPARSEMEM_VMEMMAP. Specifically,
hugetlb can pre-HVO bootmem allocated pages that way, so that no time and
resources are wasted on allocating vmemmap pages, only to free them later
(and possibly unnecessarily running the system out of memory in the
process).
Refactor some code and export a few convenience functions for external
use.
In sparse_init_nid, skip any sections that are already initialized, e.g.
they have been initialized by sparse_vmemmap_init_nid_early already.
The hugetlb code to use these functions will be added in a later commit.
Export section_map_size, as any alternate memmap init code will want to
use it.
The internal config option to enable this is SPARSEMEM_VMEMMAP_PREINIT,
which is selected if an architecture-specific option,
ARCH_WANT_HUGETLB_VMEMMAP_PREINIT, is set. In the future, if other
subsystems want to do preinit too, they can do it in a similar fashion.
The internal config option is there because a section flag is used, and
the number of flags available is architecture-dependent (see mmzone.h).
Architecures can decide if there is room for the flag when enabling
options that select SPARSEMEM_VMEMMAP_PREINIT.
Fortunately, as of right now, all sparse vmemmap using architectures do
have room.
Link: https://lkml.kernel.org/r/20250228182928.2645936-11-fvdl@google.com
Signed-off-by: Frank van der Linden <fvdl@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Dan Carpenter <dan.carpenter@linaro.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Joao Martins <joao.m.martins@oracle.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Roman Gushchin (Cruise) <roman.gushchin@linux.dev>
Cc: Usama Arif <usamaarif642@gmail.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
For clarity. It's increasingly hard to reason about the code, when KASLR
is moving around the boundaries. In this case where KASLR is randomizing
the location of the kernel image within physical memory, the maximum
number of address bits for physical memory has not changed.
What has changed is the ending address of memory that is allowed to be
directly mapped by the kernel.
Let's name the variable, and the associated macro accordingly.
Also, enhance the comment above the direct_map_physmem_end definition,
to further clarify how this all works.
Link: https://lkml.kernel.org/r/20241009025024.89813-1-jhubbard@nvidia.com
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Pankaj Gupta <pankaj.gupta@amd.com>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Will Deacon <will@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Jordan Niethe <jniethe@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Pull x86 fixes from Thomas Gleixner:
- x2apic_disable() clears x2apic_state and x2apic_mode unconditionally,
even when the state is X2APIC_ON_LOCKED, which prevents the kernel to
disable it thereby creating inconsistent state.
Reorder the logic so it actually works correctly
- The XSTATE logic for handling LBR is incorrect as it assumes that
XSAVES supports LBR when the CPU supports LBR. In fact both
conditions need to be true. Otherwise the enablement of LBR in the
IA32_XSS MSR fails and subsequently the machine crashes on the next
XRSTORS operation because IA32_XSS is not initialized.
Cache the XSTATE support bit during init and make the related
functions use this cached information and the LBR CPU feature bit to
cure this.
- Cure a long standing bug in KASLR
KASLR uses the full address space between PAGE_OFFSET and vaddr_end
to randomize the starting points of the direct map, vmalloc and
vmemmap regions. It thereby limits the size of the direct map by
using the installed memory size plus an extra configurable margin for
hot-plug memory. This limitation is done to gain more randomization
space because otherwise only the holes between the direct map,
vmalloc, vmemmap and vaddr_end would be usable for randomizing.
The limited direct map size is not exposed to the rest of the kernel,
so the memory hot-plug and resource management related code paths
still operate under the assumption that the available address space
can be determined with MAX_PHYSMEM_BITS.
request_free_mem_region() allocates from (1 << MAX_PHYSMEM_BITS) - 1
downwards. That means the first allocation happens past the end of
the direct map and if unlucky this address is in the vmalloc space,
which causes high_memory to become greater than VMALLOC_START and
consequently causes iounmap() to fail for valid ioremap addresses.
Cure this by exposing the end of the direct map via PHYSMEM_END and
use that for the memory hot-plug and resource management related
places instead of relying on MAX_PHYSMEM_BITS. In the KASLR case
PHYSMEM_END maps to a variable which is initialized by the KASLR
initialization and otherwise it is based on MAX_PHYSMEM_BITS as
before.
- Prevent a data leak in mmio_read(). The TDVMCALL exposes the value of
an initialized variabled on the stack to the VMM. The variable is
only required as output value, so it does not have to exposed to the
VMM in the first place.
- Prevent an array overrun in the resource control code on systems with
Sub-NUMA Clustering enabled because the code failed to adjust the
index by the number of SNC nodes per L3 cache.
* tag 'x86-urgent-2024-09-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/resctrl: Fix arch_mbm_* array overrun on SNC
x86/tdx: Fix data leak in mmio_read()
x86/kaslr: Expose and use the end of the physical memory address space
x86/fpu: Avoid writing LBR bit to IA32_XSS unless supported
x86/apic: Make x2apic_disable() work correctly
iounmap() on x86 occasionally fails to unmap because the provided valid
ioremap address is not below high_memory. It turned out that this
happens due to KASLR.
KASLR uses the full address space between PAGE_OFFSET and vaddr_end to
randomize the starting points of the direct map, vmalloc and vmemmap
regions. It thereby limits the size of the direct map by using the
installed memory size plus an extra configurable margin for hot-plug
memory. This limitation is done to gain more randomization space
because otherwise only the holes between the direct map, vmalloc,
vmemmap and vaddr_end would be usable for randomizing.
The limited direct map size is not exposed to the rest of the kernel, so
the memory hot-plug and resource management related code paths still
operate under the assumption that the available address space can be
determined with MAX_PHYSMEM_BITS.
request_free_mem_region() allocates from (1 << MAX_PHYSMEM_BITS) - 1
downwards. That means the first allocation happens past the end of the
direct map and if unlucky this address is in the vmalloc space, which
causes high_memory to become greater than VMALLOC_START and consequently
causes iounmap() to fail for valid ioremap addresses.
MAX_PHYSMEM_BITS cannot be changed for that because the randomization
does not align with address bit boundaries and there are other places
which actually require to know the maximum number of address bits. All
remaining usage sites of MAX_PHYSMEM_BITS have been analyzed and found
to be correct.
Cure this by exposing the end of the direct map via PHYSMEM_END and use
that for the memory hot-plug and resource management related places
instead of relying on MAX_PHYSMEM_BITS. In the KASLR case PHYSMEM_END
maps to a variable which is initialized by the KASLR initialization and
otherwise it is based on MAX_PHYSMEM_BITS as before.
To prevent future hickups add a check into add_pages() to catch callers
trying to add memory above PHYSMEM_END.
Fixes: 0483e1fa6e ("x86/mm: Implement ASLR for kernel memory regions")
Reported-by: Max Ramanouski <max8rr8@gmail.com>
Reported-by: Alistair Popple <apopple@nvidia.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-By: Max Ramanouski <max8rr8@gmail.com>
Tested-by: Alistair Popple <apopple@nvidia.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Alistair Popple <apopple@nvidia.com>
Reviewed-by: Kees Cook <kees@kernel.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/87ed6soy3z.ffs@tglx
Fix invalid access to pgdat during hot-remove operation:
ndctl users reported a GPF when trying to destroy a namespace:
$ ndctl destroy-namespace all -r all -f
Segmentation fault
dmesg:
Oops: general protection fault, probably for
non-canonical address 0xdffffc0000005650: 0000 [#1] PREEMPT SMP KASAN
PTI
KASAN: probably user-memory-access in range
[0x000000000002b280-0x000000000002b287]
CPU: 26 UID: 0 PID: 1868 Comm: ndctl Not tainted 6.11.0-rc1 #1
Hardware name: Dell Inc. PowerEdge R640/08HT8T, BIOS
2.20.1 09/13/2023
RIP: 0010:mod_node_page_state+0x2a/0x110
cxl-test users report a GPF when trying to unload the test module:
$ modrpobe -r cxl-test
dmesg
BUG: unable to handle page fault for address: 0000000000004200
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 0 P4D 0
Oops: Oops: 0000 [#1] PREEMPT SMP PTI
CPU: 0 UID: 0 PID: 1076 Comm: modprobe Tainted: G O N 6.11.0-rc1 #197
Tainted: [O]=OOT_MODULE, [N]=TEST
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/15
RIP: 0010:mod_node_page_state+0x6/0x90
Currently, when memory is hot-plugged or hot-removed the accounting is
done based on the assumption that memmap is allocated from the same node
as the hot-plugged/hot-removed memory, which is not always the case.
In addition, there are challenges with keeping the node id of the memory
that is being remove to the time when memmap accounting is actually
performed: since this is done after remove_pfn_range_from_zone(), and
also after remove_memory_block_devices(). Meaning that we cannot use
pgdat nor walking though memblocks to get the nid.
Given all of that, account the memmap overhead system wide instead.
For this we are going to be using global atomic counters, but given that
memmap size is rarely modified, and normally is only modified either
during early boot when there is only one CPU, or under a hotplug global
mutex lock, therefore there is no need for per-cpu optimizations.
Also, while we are here rename nr_memmap to nr_memmap_pages, and
nr_memmap_boot to nr_memmap_boot_pages to be self explanatory that the
units are in page count.
[pasha.tatashin@soleen.com: address a few nits from David Hildenbrand]
Link: https://lkml.kernel.org/r/20240809191020.1142142-4-pasha.tatashin@soleen.com
Link: https://lkml.kernel.org/r/20240809191020.1142142-4-pasha.tatashin@soleen.com
Link: https://lkml.kernel.org/r/20240808213437.682006-4-pasha.tatashin@soleen.com
Fixes: 15995a3524 ("mm: report per-page metadata information")
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reported-by: Yi Zhang <yi.zhang@redhat.com>
Closes: https://lore.kernel.org/linux-cxl/CAHj4cs9Ax1=CoJkgBGP_+sNu6-6=6v=_L-ZBZY0bVLD3wUWZQg@mail.gmail.com
Reported-by: Alison Schofield <alison.schofield@intel.com>
Closes: https://lore.kernel.org/linux-mm/Zq0tPd2h6alFz8XF@aschofie-mobl2/#t
Tested-by: Dan Williams <dan.j.williams@intel.com>
Tested-by: Alison Schofield <alison.schofield@intel.com>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: David Rientjes <rientjes@google.com>
Tested-by: Yi Zhang <yi.zhang@redhat.com>
Cc: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Cc: Fan Ni <fan.ni@samsung.com>
Cc: Joel Granados <j.granados@samsung.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Li Zhijian <lizhijian@fujitsu.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Sourav Panda <souravpanda@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Today, we do not have any observability of per-page metadata and how much
it takes away from the machine capacity. Thus, we want to describe the
amount of memory that is going towards per-page metadata, which can vary
depending on build configuration, machine architecture, and system use.
This patch adds 2 fields to /proc/vmstat that can used as shown below:
Accounting per-page metadata allocated by boot-allocator:
/proc/vmstat:nr_memmap_boot * PAGE_SIZE
Accounting per-page metadata allocated by buddy-allocator:
/proc/vmstat:nr_memmap * PAGE_SIZE
Accounting total Perpage metadata allocated on the machine:
(/proc/vmstat:nr_memmap_boot +
/proc/vmstat:nr_memmap) * PAGE_SIZE
Utility for userspace:
Observability: Describe the amount of memory overhead that is going to
per-page metadata on the system at any given time since this overhead is
not currently observable.
Debugging: Tracking the changes or absolute value in struct pages can help
detect anomalies as they can be correlated with other metrics in the
machine (e.g., memtotal, number of huge pages, etc).
page_ext overheads: Some kernel features such as page_owner
page_table_check that use page_ext can be optionally enabled via kernel
parameters. Having the total per-page metadata information helps users
precisely measure impact. Furthermore, page-metadata metrics will reflect
the amount of struct pages reliquished (or overhead reduced) when
hugetlbfs pages are reserved which will vary depending on whether hugetlb
vmemmap optimization is enabled or not.
For background and results see:
lore.kernel.org/all/20240220214558.3377482-1-souravpanda@google.com
Link: https://lkml.kernel.org/r/20240605222751.1406125-1-souravpanda@google.com
Signed-off-by: Sourav Panda <souravpanda@google.com>
Acked-by: David Rientjes <rientjes@google.com>
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Chen Linxuan <chenlinxuan@uniontech.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ivan Babrou <ivan@cloudflare.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Tomas Mudrunka <tomas.mudrunka@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Xu <weixugc@google.com>
Cc: Yang Yang <yang.yang29@zte.com.cn>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
