tjh.dev/kernel at 864ad046c15758747809d9397cae621540493bcb

The swiotlb does not support a mapping size > swiotlb_max_mapping_size().
On the other hand, with a 64KB PAGE_SIZE configuration, it's observed that
an NVME device can map a size between 300KB~512KB, which certainly failed
the swiotlb mappings, though the default pool of swiotlb has many slots:
systemd[1]: Started Journal Service.
=> nvme 0000:00:01.0: swiotlb buffer is full (sz: 327680 bytes), total 32768 (slots), used 32 (slots)
note: journal-offline[392] exited with irqs disabled
note: journal-offline[392] exited with preempt_count 1

Call trace:
[ 3.099918] swiotlb_tbl_map_single+0x214/0x240
[ 3.099921] iommu_dma_map_page+0x218/0x328
[ 3.099928] dma_map_page_attrs+0x2e8/0x3a0
[ 3.101985] nvme_prep_rq.part.0+0x408/0x878 [nvme]
[ 3.102308] nvme_queue_rqs+0xc0/0x300 [nvme]
[ 3.102313] blk_mq_flush_plug_list.part.0+0x57c/0x600
[ 3.102321] blk_add_rq_to_plug+0x180/0x2a0
[ 3.102323] blk_mq_submit_bio+0x4c8/0x6b8
[ 3.103463] __submit_bio+0x44/0x220
[ 3.103468] submit_bio_noacct_nocheck+0x2b8/0x360
[ 3.103470] submit_bio_noacct+0x180/0x6c8
[ 3.103471] submit_bio+0x34/0x130
[ 3.103473] ext4_bio_write_folio+0x5a4/0x8c8
[ 3.104766] mpage_submit_folio+0xa0/0x100
[ 3.104769] mpage_map_and_submit_buffers+0x1a4/0x400
[ 3.104771] ext4_do_writepages+0x6a0/0xd78
[ 3.105615] ext4_writepages+0x80/0x118
[ 3.105616] do_writepages+0x90/0x1e8
[ 3.105619] filemap_fdatawrite_wbc+0x94/0xe0
[ 3.105622] __filemap_fdatawrite_range+0x68/0xb8
[ 3.106656] file_write_and_wait_range+0x84/0x120
[ 3.106658] ext4_sync_file+0x7c/0x4c0
[ 3.106660] vfs_fsync_range+0x3c/0xa8
[ 3.106663] do_fsync+0x44/0xc0

Since untrusted devices might go down the swiotlb pathway with dma-iommu,
these devices should not map a size larger than swiotlb_max_mapping_size.

To fix this bug, add iommu_dma_max_mapping_size() for untrusted devices to
take into account swiotlb_max_mapping_size() v.s. iova_rcache_range() from
the iommu_dma_opt_mapping_size().

Fixes: 82612d66d51d ("iommu: Allow the dma-iommu api to use bounce buffers")
Link: https://lore.kernel.org/r/ee51a3a5c32cf885b18f6416171802669f4a718a.1707851466.git.nicolinc@nvidia.com
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
[will: Drop redundant is_swiotlb_active(dev) check]
Signed-off-by: Will Deacon <will@kernel.org>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Acked-by: Robin Murphy <robin.murphy@arm.com>
Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Tested-by: Michael Kelley <mhklinux@outlook.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

afc5aa46

Nicolin Chen

2 years ago

Merge tag 'irq-urgent-2024-03-23' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

1a391931

Linus Torvalds

2 years ago

Merge tag 'timers-v6.9-rc1' of https://git.linaro.org/people/daniel.lezcano/linux into timers/core

86c54c84

Thomas Gleixner

2 years ago

timers/migration: Fix endless timer requeue after idle interrupts

When a CPU is an idle migrator, but another CPU wakes up before it,
becomes an active migrator and handles the queue, the initial idle
migrator may end up endlessly reprogramming its clockevent, chasing ghost
timers forever such as in the following scenario:

[GRP0:0]
migrator = 0
active = 0
nextevt = T1
/ \
0 1
active idle (T1)

0) CPU 1 is idle and has a timer queued (T1), CPU 0 is active and is
the active migrator.

[GRP0:0]
migrator = NONE
active = NONE
nextevt = T1
/ \
0 1
idle idle (T1)
wakeup = T1

1) CPU 0 is now idle and is therefore the idle migrator. It has
programmed its next timer interrupt to handle T1.

[GRP0:0]
migrator = 1
active = 1
nextevt = KTIME_MAX
/ \
0 1
idle active
wakeup = T1

2) CPU 1 has woken up, it is now active and it has just handled its own
timer T1.

3) CPU 0 gets a timer interrupt to handle T1 but tmigr_handle_remote()
realize it is not the migrator anymore. So it early returns without
observing that T1 has been expired already and therefore without
updating its ->wakeup value.

4) CPU 0 goes into tmigr_cpu_new_timer() which also early returns
because it doesn't queue a timer of its own. So ->wakeup is left
unchanged and the next timer is programmed to fire now.

5) goto 3) forever

This results in timer interrupt storms in idle and also in nohz_full (as
observed in rcutorture's TREE07 scenario).

Fix this with forcing a re-evaluation of tmc->wakeup while trying
remote timer handling when the CPU isn't the migrator anymmore. The
check is inherently racy but in the worst case the CPU just races setting
the KTIME_MAX value that a remote expiry also tries to set.

Fixes: 7ee988770326 ("timers: Implement the hierarchical pull model")
Reported-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240318230729.15497-2-frederic@kernel.org

f55acb1e

Frederic Weisbecker

2 years ago

swiotlb: Fix alignment checks when both allocation and DMA masks are present

51b30ecb

Will Deacon

2 years ago

Merge tag 'core-entry-2024-03-23' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

976b029d

Linus Torvalds

2 years ago

irqchip/renesas-rzg2l: Do not set TIEN and TINT source at the same time

dce0919c

Biju Das

2 years ago

timer/migration: Fix quick check reporting late expiry

When a CPU is the last active in the hierarchy and it tries to enter
into idle, the quick check looking up the next event towards cpuidle
heuristics may report a too late expiry, such as in the following
scenario:

[GRP1:0]
migrator = NONE
active = NONE
nextevt = T0:0, T0:1
/ \
[GRP0:0] [GRP0:1]
migrator = NONE migrator = NONE
active = NONE active = NONE
nextevt = T0, T1 nextevt = T2
/ \ / \
0 1 2 3
idle idle idle idle

0) The whole system is idle, and CPU 0 was the last migrator. CPU 0 has
a timer (T0), CPU 1 has a timer (T1) and CPU 2 has a timer (T2). The
expire order is T0 < T1 < T2.

[GRP1:0]
migrator = GRP0:0
active = GRP0:0
nextevt = T0:0(i), T0:1
/ \
[GRP0:0] [GRP0:1]
migrator = CPU0 migrator = NONE
active = CPU0 active = NONE
nextevt = T0(i), T1 nextevt = T2
/ \ / \
0 1 2 3
active idle idle idle

1) CPU 0 becomes active. The (i) means a now ignored timer.

[GRP1:0]
migrator = GRP0:0
active = GRP0:0
nextevt = T0:1
/ \
[GRP0:0] [GRP0:1]
migrator = CPU0 migrator = NONE
active = CPU0 active = NONE
nextevt = T1 nextevt = T2
/ \ / \
0 1 2 3
active idle idle idle

2) CPU 0 handles remote. No timer actually expired but ignored timers
have been cleaned out and their sibling's timers haven't been
propagated. As a result the top level's next event is T2 and not T1.

3) CPU 0 tries to enter idle without any global timer enqueued and calls
tmigr_quick_check(). The expiry of T2 is returned instead of the
expiry of T1.

When the quick check returns an expiry that is too late, the cpuidle
governor may pick up a C-state that is too deep. This may be result into
undesired CPU wake up latency if the next timer is actually close enough.

Fix this with assuming that expiries aren't sorted top-down while
performing the quick check. Pick up instead the earliest encountered one
while walking up the hierarchy.

7ee988770326 ("timers: Implement the hierarchical pull model")
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240305002822.18130-1-frederic@kernel.org

8ca18367

Frederic Weisbecker

2 years ago

clocksource/drivers/timer-riscv: Clear timer interrupt on timer initialization

8248ca30

Ley Foon Tan

2 years ago

timer/migration: Remove buggy early return on deactivation

When a CPU enters into idle and deactivates itself from the timer
migration hierarchy without any global timer of its own to propagate,
the group event of that CPU is set to "ignore" and tmigr_update_events()
accordingly performs an early return without considering timers queued
by other CPUs.

If the hierarchy has a single level, and the CPU is the last one to
enter idle, it will ignore others' global timers, as in the following
layout:

[GRP0:0]
migrator = 0
active = 0
nextevt = T0i
/ \
0 1
active (T0i) idle (T1)

0) CPU 0 is active thus its event is ignored (the letter 'i') and so are
upper levels' events. CPU 1 is idle and has the timer T1 enqueued.

[GRP0:0]
migrator = NONE
active = NONE
nextevt = T0i
/ \
0 1
idle (T0i) idle (T1)

1) CPU 0 goes idle without global event queued. Therefore KTIME_MAX is
pushed as its next expiry and its own event kept as "ignore". As a result
tmigr_update_events() ignores T1 and CPU 0 goes to idle with T1
unhandled.

This isn't proper to single level hierarchy though. A similar issue,
although slightly different, may arise on multi-level:

[GRP1:0]
migrator = GRP0:0
active = GRP0:0
nextevt = T0:0i, T0:1
/ \
[GRP0:0] [GRP0:1]
migrator = 0 migrator = NONE
active = 0 active = NONE
nextevt = T0i nextevt = T2
/ \ / \
0 (T0i) 1 (T1) 2 (T2) 3
active idle idle idle

0) CPU 0 is active thus its event is ignored (the letter 'i') and so are
upper levels' events. CPU 1 is idle and has the timer T1 enqueued.
CPU 2 also has a timer. The expiry order is T0 (ignored) < T1 < T2

[GRP1:0]
migrator = GRP0:0
active = GRP0:0
nextevt = T0:0i, T0:1
/ \
[GRP0:0] [GRP0:1]
migrator = NONE migrator = NONE
active = NONE active = NONE
nextevt = T0i nextevt = T2
/ \ / \
0 (T0i) 1 (T1) 2 (T2) 3
idle idle idle idle

1) CPU 0 goes idle without global event queued. Therefore KTIME_MAX is
pushed as its next expiry and its own event kept as "ignore". As a result
tmigr_update_events() ignores T1. The change only propagated up to 1st
level so far.

[GRP1:0]
migrator = NONE
active = NONE
nextevt = T0:1
/ \
[GRP0:0] [GRP0:1]
migrator = NONE migrator = NONE
active = NONE active = NONE
nextevt = T0i nextevt = T2
/ \ / \
0 (T0i) 1 (T1) 2 (T2) 3
idle idle idle idle

2) The change now propagates up to the top. tmigr_update_events() finds
that the child event is ignored and thus removes it. The top level next
event is now T2 which is returned to CPU 0 as its next effective expiry
to take account for as the global idle migrator. However T1 has been
ignored along the way, leaving it unhandled.

Fix those issues with removing the buggy related early return. Ignored
child events must not prevent from evaluating the other events within
the same group.

Reported-by: Boqun Feng <boqun.feng@gmail.com>
Reported-by: Florian Fainelli <f.fainelli@gmail.com>
Reported-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Florian Fainelli <florian.fainelli@broadcom.com>
Link: https://lore.kernel.org/r/ZfOhB9ZByTZcBy4u@lothringen

4b6f4c5a

Frederic Weisbecker

2 years ago

branches 3

master 1 day ago default

compare

nocache-cleanup 4 weeks ago

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for-next 1 year ago

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tags 928

v7.1-rc1

2 days ago latest

README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
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In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.

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