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Keith Busch bcbad21fe9 vfio/type1: conditional rescheduling while pinning 
[ Upstream commit b1779e4f20 ]

A large DMA mapping request can loop through dma address pinning for
many pages. In cases where THP can not be used, the repeated vmf_insert_pfn can
be costly, so let the task reschedule as need to prevent CPU stalls. Failure to
do so has potential harmful side effects, like increased memory pressure
as unrelated rcu tasks are unable to make their reclaim callbacks and
result in OOM conditions.

 rcu: INFO: rcu_sched self-detected stall on CPU
 rcu:   36-....: (20999 ticks this GP) idle=b01c/1/0x4000000000000000 softirq=35839/35839 fqs=3538
 rcu:            hardirqs   softirqs   csw/system
 rcu:    number:        0        107            0
 rcu:   cputime:       50          0        10446   ==> 10556(ms)
 rcu:   (t=21075 jiffies g=377761 q=204059 ncpus=384)
...
  <TASK>
  ? asm_sysvec_apic_timer_interrupt+0x16/0x20
  ? walk_system_ram_range+0x63/0x120
  ? walk_system_ram_range+0x46/0x120
  ? pgprot_writethrough+0x20/0x20
  lookup_memtype+0x67/0xf0
  track_pfn_insert+0x20/0x40
  vmf_insert_pfn_prot+0x88/0x140
  vfio_pci_mmap_huge_fault+0xf9/0x1b0 [vfio_pci_core]
  __do_fault+0x28/0x1b0
  handle_mm_fault+0xef1/0x2560
  fixup_user_fault+0xf5/0x270
  vaddr_get_pfns+0x169/0x2f0 [vfio_iommu_type1]
  vfio_pin_pages_remote+0x162/0x8e0 [vfio_iommu_type1]
  vfio_iommu_type1_ioctl+0x1121/0x1810 [vfio_iommu_type1]
  ? futex_wake+0x1c1/0x260
  x64_sys_call+0x234/0x17a0
  do_syscall_64+0x63/0x130
  ? exc_page_fault+0x63/0x130
  entry_SYSCALL_64_after_hwframe+0x4b/0x53

Signed-off-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Link: https://lore.kernel.org/r/20250715184622.3561598-1-kbusch@meta.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2025-08-20 18:30:47 +02:00
arch MIPS: lantiq: falcon: sysctrl: fix request memory check logic 2025-08-20 18:30:43 +02:00
block block: ensure discard_granularity is zero when discard is not supported 2025-08-15 12:14:05 +02:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: jitter - fix intermediary handling 2025-08-20 18:30:42 +02:00
Documentation Documentation: ACPI: Fix parent device references 2025-08-20 18:30:15 +02:00
drivers vfio/type1: conditional rescheduling while pinning 2025-08-20 18:30:47 +02:00
fs f2fs: check the generic conditions first 2025-08-20 18:30:47 +02:00
include vsock/virtio: Resize receive buffers so that each SKB fits in a 4K page 2025-08-20 18:30:40 +02:00
init io_uring: fix breakage in EXPERT menu 2025-08-15 12:13:32 +02:00
io_uring io_uring/poll: fix POLLERR handling 2025-07-24 08:56:23 +02:00
ipc ipc: fix to protect IPCS lookups using RCU 2025-06-27 11:11:22 +01:00
kernel printk: nbcon: Allow reacquire during panic 2025-08-20 18:30:47 +02:00
lib lib/alloc_tag: do not acquire non-existent lock in alloc_tag_top_users() 2025-07-17 18:37:14 +02:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm mm: swap: fix potential buffer overflow in setup_clusters() 2025-08-15 12:14:14 +02:00
net vsock/virtio: Resize receive buffers so that each SKB fits in a 4K page 2025-08-20 18:30:40 +02:00
rust rust: use #[used(compiler)] to fix build and modpost with Rust >= 1.89.0 2025-07-24 08:56:37 +02:00
samples samples: mei: Fix building on musl libc 2025-08-15 12:13:38 +02:00
scripts kconfig: lxdialog: replace strcpy() with strncpy() in inputbox.c 2025-08-20 18:30:47 +02:00
security apparmor: fix x_table_lookup when stacking is not the first entry 2025-08-20 18:30:47 +02:00
sound ASoC: qcom: use drvdata instead of component to keep id 2025-08-20 18:30:28 +02:00
tools selftests/bpf: Fix a user_ringbuf failure with arm64 64KB page size 2025-08-20 18:30:39 +02:00
usr kbuild: hdrcheck: fix cross build with clang 2025-03-13 13:02:18 +01:00
virt KVM: Allow CPU to reschedule while setting per-page memory attributes 2025-07-17 18:37:08 +02:00
.clang-format clang-format: Update with v6.11-rc1's for_each macro list 2024-08-02 13:20:31 +02:00
.clippy.toml rust: give Clippy the minimum supported Rust version 2025-08-01 09:48:44 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore Add Jeff Kirsher to .get_maintainer.ignore 2024-03-08 11:36:54 +00:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore rust: introduce .clippy.toml 2025-03-13 13:01:42 +01:00
.mailmap mailmap: add entry for Thorsten Blum 2024-11-07 14:14:59 -08:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Remove self from DSA entry 2024-11-03 12:52:38 -08:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS MAINTAINERS: Update Alexey Makhalov's email address 2025-05-22 14:29:46 +02:00
Makefile Linux 6.12.42 2025-08-15 12:14:14 +02:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

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
Documentation/admin-guide/README.rst first.

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.