Commit 50e782a86c ("efi/unaccepted: Fix soft lockups caused by
parallel memory acceptance") has released the spinlock so other CPUs can
do memory acceptance in parallel and not triggers softlockup on other
CPUs.
However the softlock up was intermittent shown up if the memory of the
TD guest is large, and the timeout of softlockup is set to 1 second:
RIP: 0010:_raw_spin_unlock_irqrestore
Call Trace:
? __hrtimer_run_queues
<IRQ>
? hrtimer_interrupt
? watchdog_timer_fn
? __sysvec_apic_timer_interrupt
? __pfx_watchdog_timer_fn
? sysvec_apic_timer_interrupt
</IRQ>
? __hrtimer_run_queues
<TASK>
? hrtimer_interrupt
? asm_sysvec_apic_timer_interrupt
? _raw_spin_unlock_irqrestore
? __sysvec_apic_timer_interrupt
? sysvec_apic_timer_interrupt
accept_memory
try_to_accept_memory
do_huge_pmd_anonymous_page
get_page_from_freelist
__handle_mm_fault
__alloc_pages
__folio_alloc
? __tdx_hypercall
handle_mm_fault
vma_alloc_folio
do_user_addr_fault
do_huge_pmd_anonymous_page
exc_page_fault
? __do_huge_pmd_anonymous_page
asm_exc_page_fault
__handle_mm_fault
When the local irq is enabled at the end of accept_memory(), the
softlockup detects that the watchdog on single CPU has not been fed for
a while. That is to say, even other CPUs will not be blocked by
spinlock, the current CPU might be stunk with local irq disabled for a
while, which hurts not only nmi watchdog but also softlockup.
Chao Gao pointed out that the memory accept could be time costly and
there was similar report before. Thus to avoid any softlocup detection
during this stage, give the softlockup a flag to skip the timeout check
at the end of accept_memory(), by invoking touch_softlockup_watchdog().
Reported-by: Hossain, Md Iqbal <md.iqbal.hossain@intel.com>
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Fixes: 50e782a86c ("efi/unaccepted: Fix soft lockups caused by parallel memory acceptance")
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
When a task needs to accept memory it will scan the accepting_list
to see if any ranges already being processed by other tasks overlap
with its range. Due to an off-by-one in the range comparisons, a task
might falsely determine that an overlapping range is being accepted,
leading to an unnecessary delay before it begins processing the range.
Fix the off-by-one in the range comparison to prevent this and slightly
improve performance.
Fixes: 50e782a86c ("efi/unaccepted: Fix soft lockups caused by parallel memory acceptance")
Link: https://lore.kernel.org/linux-mm/20231101004523.vseyi5bezgfaht5i@amd.com/T/#me2eceb9906fcae5fe958b3fe88e41f920f8335b6
Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
included in this merge do the following:
- Kemeng Shi has contributed some compation maintenance work in the
series "Fixes and cleanups to compaction".
- Joel Fernandes has a patchset ("Optimize mremap during mutual
alignment within PMD") which fixes an obscure issue with mremap()'s
pagetable handling during a subsequent exec(), based upon an
implementation which Linus suggested.
- More DAMON/DAMOS maintenance and feature work from SeongJae Park i the
following patch series:
mm/damon: misc fixups for documents, comments and its tracepoint
mm/damon: add a tracepoint for damos apply target regions
mm/damon: provide pseudo-moving sum based access rate
mm/damon: implement DAMOS apply intervals
mm/damon/core-test: Fix memory leaks in core-test
mm/damon/sysfs-schemes: Do DAMOS tried regions update for only one apply interval
- In the series "Do not try to access unaccepted memory" Adrian Hunter
provides some fixups for the recently-added "unaccepted memory' feature.
To increase the feature's checking coverage. "Plug a few gaps where
RAM is exposed without checking if it is unaccepted memory".
- In the series "cleanups for lockless slab shrink" Qi Zheng has done
some maintenance work which is preparation for the lockless slab
shrinking code.
- Qi Zheng has redone the earlier (and reverted) attempt to make slab
shrinking lockless in the series "use refcount+RCU method to implement
lockless slab shrink".
- David Hildenbrand contributes some maintenance work for the rmap code
in the series "Anon rmap cleanups".
- Kefeng Wang does more folio conversions and some maintenance work in
the migration code. Series "mm: migrate: more folio conversion and
unification".
- Matthew Wilcox has fixed an issue in the buffer_head code which was
causing long stalls under some heavy memory/IO loads. Some cleanups
were added on the way. Series "Add and use bdev_getblk()".
- In the series "Use nth_page() in place of direct struct page
manipulation" Zi Yan has fixed a potential issue with the direct
manipulation of hugetlb page frames.
- In the series "mm: hugetlb: Skip initialization of gigantic tail
struct pages if freed by HVO" has improved our handling of gigantic
pages in the hugetlb vmmemmep optimizaton code. This provides
significant boot time improvements when significant amounts of gigantic
pages are in use.
- Matthew Wilcox has sent the series "Small hugetlb cleanups" - code
rationalization and folio conversions in the hugetlb code.
- Yin Fengwei has improved mlock()'s handling of large folios in the
series "support large folio for mlock"
- In the series "Expose swapcache stat for memcg v1" Liu Shixin has
added statistics for memcg v1 users which are available (and useful)
under memcg v2.
- Florent Revest has enhanced the MDWE (Memory-Deny-Write-Executable)
prctl so that userspace may direct the kernel to not automatically
propagate the denial to child processes. The series is named "MDWE
without inheritance".
- Kefeng Wang has provided the series "mm: convert numa balancing
functions to use a folio" which does what it says.
- In the series "mm/ksm: add fork-exec support for prctl" Stefan Roesch
makes is possible for a process to propagate KSM treatment across
exec().
- Huang Ying has enhanced memory tiering's calculation of memory
distances. This is used to permit the dax/kmem driver to use "high
bandwidth memory" in addition to Optane Data Center Persistent Memory
Modules (DCPMM). The series is named "memory tiering: calculate
abstract distance based on ACPI HMAT"
- In the series "Smart scanning mode for KSM" Stefan Roesch has
optimized KSM by teaching it to retain and use some historical
information from previous scans.
- Yosry Ahmed has fixed some inconsistencies in memcg statistics in the
series "mm: memcg: fix tracking of pending stats updates values".
- In the series "Implement IOCTL to get and optionally clear info about
PTEs" Peter Xu has added an ioctl to /proc/<pid>/pagemap which permits
us to atomically read-then-clear page softdirty state. This is mainly
used by CRIU.
- Hugh Dickins contributed the series "shmem,tmpfs: general maintenance"
- a bunch of relatively minor maintenance tweaks to this code.
- Matthew Wilcox has increased the use of the VMA lock over file-backed
page faults in the series "Handle more faults under the VMA lock". Some
rationalizations of the fault path became possible as a result.
- In the series "mm/rmap: convert page_move_anon_rmap() to
folio_move_anon_rmap()" David Hildenbrand has implemented some cleanups
and folio conversions.
- In the series "various improvements to the GUP interface" Lorenzo
Stoakes has simplified and improved the GUP interface with an eye to
providing groundwork for future improvements.
- Andrey Konovalov has sent along the series "kasan: assorted fixes and
improvements" which does those things.
- Some page allocator maintenance work from Kemeng Shi in the series
"Two minor cleanups to break_down_buddy_pages".
- In thes series "New selftest for mm" Breno Leitao has developed
another MM self test which tickles a race we had between madvise() and
page faults.
- In the series "Add folio_end_read" Matthew Wilcox provides cleanups
and an optimization to the core pagecache code.
- Nhat Pham has added memcg accounting for hugetlb memory in the series
"hugetlb memcg accounting".
- Cleanups and rationalizations to the pagemap code from Lorenzo
Stoakes, in the series "Abstract vma_merge() and split_vma()".
- Audra Mitchell has fixed issues in the procfs page_owner code's new
timestamping feature which was causing some misbehaviours. In the
series "Fix page_owner's use of free timestamps".
- Lorenzo Stoakes has fixed the handling of new mappings of sealed files
in the series "permit write-sealed memfd read-only shared mappings".
- Mike Kravetz has optimized the hugetlb vmemmap optimization in the
series "Batch hugetlb vmemmap modification operations".
- Some buffer_head folio conversions and cleanups from Matthew Wilcox in
the series "Finish the create_empty_buffers() transition".
- As a page allocator performance optimization Huang Ying has added
automatic tuning to the allocator's per-cpu-pages feature, in the series
"mm: PCP high auto-tuning".
- Roman Gushchin has contributed the patchset "mm: improve performance
of accounted kernel memory allocations" which improves their performance
by ~30% as measured by a micro-benchmark.
- folio conversions from Kefeng Wang in the series "mm: convert page
cpupid functions to folios".
- Some kmemleak fixups in Liu Shixin's series "Some bugfix about
kmemleak".
- Qi Zheng has improved our handling of memoryless nodes by keeping them
off the allocation fallback list. This is done in the series "handle
memoryless nodes more appropriately".
- khugepaged conversions from Vishal Moola in the series "Some
khugepaged folio conversions".
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Merge tag 'mm-stable-2023-11-01-14-33' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Pull MM updates from Andrew Morton:
"Many singleton patches against the MM code. The patch series which are
included in this merge do the following:
- Kemeng Shi has contributed some compation maintenance work in the
series 'Fixes and cleanups to compaction'
- Joel Fernandes has a patchset ('Optimize mremap during mutual
alignment within PMD') which fixes an obscure issue with mremap()'s
pagetable handling during a subsequent exec(), based upon an
implementation which Linus suggested
- More DAMON/DAMOS maintenance and feature work from SeongJae Park i
the following patch series:
mm/damon: misc fixups for documents, comments and its tracepoint
mm/damon: add a tracepoint for damos apply target regions
mm/damon: provide pseudo-moving sum based access rate
mm/damon: implement DAMOS apply intervals
mm/damon/core-test: Fix memory leaks in core-test
mm/damon/sysfs-schemes: Do DAMOS tried regions update for only one apply interval
- In the series 'Do not try to access unaccepted memory' Adrian
Hunter provides some fixups for the recently-added 'unaccepted
memory' feature. To increase the feature's checking coverage. 'Plug
a few gaps where RAM is exposed without checking if it is
unaccepted memory'
- In the series 'cleanups for lockless slab shrink' Qi Zheng has done
some maintenance work which is preparation for the lockless slab
shrinking code
- Qi Zheng has redone the earlier (and reverted) attempt to make slab
shrinking lockless in the series 'use refcount+RCU method to
implement lockless slab shrink'
- David Hildenbrand contributes some maintenance work for the rmap
code in the series 'Anon rmap cleanups'
- Kefeng Wang does more folio conversions and some maintenance work
in the migration code. Series 'mm: migrate: more folio conversion
and unification'
- Matthew Wilcox has fixed an issue in the buffer_head code which was
causing long stalls under some heavy memory/IO loads. Some cleanups
were added on the way. Series 'Add and use bdev_getblk()'
- In the series 'Use nth_page() in place of direct struct page
manipulation' Zi Yan has fixed a potential issue with the direct
manipulation of hugetlb page frames
- In the series 'mm: hugetlb: Skip initialization of gigantic tail
struct pages if freed by HVO' has improved our handling of gigantic
pages in the hugetlb vmmemmep optimizaton code. This provides
significant boot time improvements when significant amounts of
gigantic pages are in use
- Matthew Wilcox has sent the series 'Small hugetlb cleanups' - code
rationalization and folio conversions in the hugetlb code
- Yin Fengwei has improved mlock()'s handling of large folios in the
series 'support large folio for mlock'
- In the series 'Expose swapcache stat for memcg v1' Liu Shixin has
added statistics for memcg v1 users which are available (and
useful) under memcg v2
- Florent Revest has enhanced the MDWE (Memory-Deny-Write-Executable)
prctl so that userspace may direct the kernel to not automatically
propagate the denial to child processes. The series is named 'MDWE
without inheritance'
- Kefeng Wang has provided the series 'mm: convert numa balancing
functions to use a folio' which does what it says
- In the series 'mm/ksm: add fork-exec support for prctl' Stefan
Roesch makes is possible for a process to propagate KSM treatment
across exec()
- Huang Ying has enhanced memory tiering's calculation of memory
distances. This is used to permit the dax/kmem driver to use 'high
bandwidth memory' in addition to Optane Data Center Persistent
Memory Modules (DCPMM). The series is named 'memory tiering:
calculate abstract distance based on ACPI HMAT'
- In the series 'Smart scanning mode for KSM' Stefan Roesch has
optimized KSM by teaching it to retain and use some historical
information from previous scans
- Yosry Ahmed has fixed some inconsistencies in memcg statistics in
the series 'mm: memcg: fix tracking of pending stats updates
values'
- In the series 'Implement IOCTL to get and optionally clear info
about PTEs' Peter Xu has added an ioctl to /proc/<pid>/pagemap
which permits us to atomically read-then-clear page softdirty
state. This is mainly used by CRIU
- Hugh Dickins contributed the series 'shmem,tmpfs: general
maintenance', a bunch of relatively minor maintenance tweaks to
this code
- Matthew Wilcox has increased the use of the VMA lock over
file-backed page faults in the series 'Handle more faults under the
VMA lock'. Some rationalizations of the fault path became possible
as a result
- In the series 'mm/rmap: convert page_move_anon_rmap() to
folio_move_anon_rmap()' David Hildenbrand has implemented some
cleanups and folio conversions
- In the series 'various improvements to the GUP interface' Lorenzo
Stoakes has simplified and improved the GUP interface with an eye
to providing groundwork for future improvements
- Andrey Konovalov has sent along the series 'kasan: assorted fixes
and improvements' which does those things
- Some page allocator maintenance work from Kemeng Shi in the series
'Two minor cleanups to break_down_buddy_pages'
- In thes series 'New selftest for mm' Breno Leitao has developed
another MM self test which tickles a race we had between madvise()
and page faults
- In the series 'Add folio_end_read' Matthew Wilcox provides cleanups
and an optimization to the core pagecache code
- Nhat Pham has added memcg accounting for hugetlb memory in the
series 'hugetlb memcg accounting'
- Cleanups and rationalizations to the pagemap code from Lorenzo
Stoakes, in the series 'Abstract vma_merge() and split_vma()'
- Audra Mitchell has fixed issues in the procfs page_owner code's new
timestamping feature which was causing some misbehaviours. In the
series 'Fix page_owner's use of free timestamps'
- Lorenzo Stoakes has fixed the handling of new mappings of sealed
files in the series 'permit write-sealed memfd read-only shared
mappings'
- Mike Kravetz has optimized the hugetlb vmemmap optimization in the
series 'Batch hugetlb vmemmap modification operations'
- Some buffer_head folio conversions and cleanups from Matthew Wilcox
in the series 'Finish the create_empty_buffers() transition'
- As a page allocator performance optimization Huang Ying has added
automatic tuning to the allocator's per-cpu-pages feature, in the
series 'mm: PCP high auto-tuning'
- Roman Gushchin has contributed the patchset 'mm: improve
performance of accounted kernel memory allocations' which improves
their performance by ~30% as measured by a micro-benchmark
- folio conversions from Kefeng Wang in the series 'mm: convert page
cpupid functions to folios'
- Some kmemleak fixups in Liu Shixin's series 'Some bugfix about
kmemleak'
- Qi Zheng has improved our handling of memoryless nodes by keeping
them off the allocation fallback list. This is done in the series
'handle memoryless nodes more appropriately'
- khugepaged conversions from Vishal Moola in the series 'Some
khugepaged folio conversions'"
[ bcachefs conflicts with the dynamically allocated shrinkers have been
resolved as per Stephen Rothwell in
https://lore.kernel.org/all/20230913093553.4290421e@canb.auug.org.au/
with help from Qi Zheng.
The clone3 test filtering conflict was half-arsed by yours truly ]
* tag 'mm-stable-2023-11-01-14-33' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (406 commits)
mm/damon/sysfs: update monitoring target regions for online input commit
mm/damon/sysfs: remove requested targets when online-commit inputs
selftests: add a sanity check for zswap
Documentation: maple_tree: fix word spelling error
mm/vmalloc: fix the unchecked dereference warning in vread_iter()
zswap: export compression failure stats
Documentation: ubsan: drop "the" from article title
mempolicy: migration attempt to match interleave nodes
mempolicy: mmap_lock is not needed while migrating folios
mempolicy: alloc_pages_mpol() for NUMA policy without vma
mm: add page_rmappable_folio() wrapper
mempolicy: remove confusing MPOL_MF_LAZY dead code
mempolicy: mpol_shared_policy_init() without pseudo-vma
mempolicy trivia: use pgoff_t in shared mempolicy tree
mempolicy trivia: slightly more consistent naming
mempolicy trivia: delete those ancient pr_debug()s
mempolicy: fix migrate_pages(2) syscall return nr_failed
kernfs: drop shared NUMA mempolicy hooks
hugetlbfs: drop shared NUMA mempolicy pretence
mm/damon/sysfs-test: add a unit test for damon_sysfs_set_targets()
...
Michael reported soft lockups on a system that has unaccepted memory.
This occurs when a user attempts to allocate and accept memory on
multiple CPUs simultaneously.
The root cause of the issue is that memory acceptance is serialized with
a spinlock, allowing only one CPU to accept memory at a time. The other
CPUs spin and wait for their turn, leading to starvation and soft lockup
reports.
To address this, the code has been modified to release the spinlock
while accepting memory. This allows for parallel memory acceptance on
multiple CPUs.
A newly introduced "accepting_list" keeps track of which memory is
currently being accepted. This is necessary to prevent parallel
acceptance of the same memory block. If a collision occurs, the lock is
released and the process is retried.
Such collisions should rarely occur. The main path for memory acceptance
is the page allocator, which accepts memory in MAX_ORDER chunks. As long
as MAX_ORDER is equal to or larger than the unit_size, collisions will
never occur because the caller fully owns the memory block being
accepted.
Aside from the page allocator, only memblock and deferered_free_range()
accept memory, but this only happens during boot.
The code has been tested with unit_size == 128MiB to trigger collisions
and validate the retry codepath.
Fixes: 2053bc57f3 ("efi: Add unaccepted memory support")
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reported-by: Michael Roth <michael.roth@amd.com
Reviewed-by: Nikolay Borisov <nik.borisov@suse.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Tested-by: Michael Roth <michael.roth@amd.com>
[ardb: drop unnecessary cpu_relax() call]
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Patch series "Do not try to access unaccepted memory", v2.
Support for unaccepted memory was added recently, refer commit
dcdfdd40fa ("mm: Add support for unaccepted memory"), whereby
a virtual machine may need to accept memory before it can be used.
Plug a few gaps where RAM is exposed without checking if it is
unaccepted memory.
This patch (of 2):
Support for unaccepted memory was added recently, refer commit
dcdfdd40fa ("mm: Add support for unaccepted memory"), whereby a virtual
machine may need to accept memory before it can be used.
Do not let /proc/vmcore try to access unaccepted memory because it can
cause the guest to fail.
For /proc/vmcore, which is read-only, this means a read or mmap of
unaccepted memory will return zeros.
Link: https://lkml.kernel.org/r/20230911112114.91323-1-adrian.hunter@intel.com
Link: https://lkml.kernel.org/r/20230911112114.91323-2-adrian.hunter@intel.com
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: Borislav Petkov (AMD) <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
load_unaligned_zeropad() can lead to unwanted loads across page boundaries.
The unwanted loads are typically harmless. But, they might be made to
totally unrelated or even unmapped memory. load_unaligned_zeropad()
relies on exception fixup (#PF, #GP and now #VE) to recover from these
unwanted loads.
But, this approach does not work for unaccepted memory. For TDX, a load
from unaccepted memory will not lead to a recoverable exception within
the guest. The guest will exit to the VMM where the only recourse is to
terminate the guest.
There are two parts to fix this issue and comprehensively avoid access
to unaccepted memory. Together these ensure that an extra "guard" page
is accepted in addition to the memory that needs to be used.
1. Implicitly extend the range_contains_unaccepted_memory(start, end)
checks up to end+unit_size if 'end' is aligned on a unit_size
boundary.
2. Implicitly extend accept_memory(start, end) to end+unit_size if 'end'
is aligned on a unit_size boundary.
Side note: This leads to something strange. Pages which were accepted
at boot, marked by the firmware as accepted and will never
_need_ to be accepted might be on unaccepted_pages list
This is a cue to ensure that the next page is accepted
before 'page' can be used.
This is an actual, real-world problem which was discovered during TDX
testing.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20230606142637.5171-7-kirill.shutemov@linux.intel.com
efi_config_parse_tables() reserves memory that holds unaccepted memory
configuration table so it won't be reused by page allocator.
Core-mm requires few helpers to support unaccepted memory:
- accept_memory() checks the range of addresses against the bitmap and
accept memory if needed.
- range_contains_unaccepted_memory() checks if anything within the
range requires acceptance.
Architectural code has to provide efi_get_unaccepted_table() that
returns pointer to the unaccepted memory configuration table.
arch_accept_memory() handles arch-specific part of memory acceptance.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20230606142637.5171-6-kirill.shutemov@linux.intel.com
Chen Yu
Michael Roth
Linus Torvalds
Kirill A. Shutemov
Adrian Hunter