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Liam Merwick 47bb584237 KVM: Allow CPU to reschedule while setting per-page memory attributes
When running an SEV-SNP guest with a sufficiently large amount of memory (1TB+),
the host can experience CPU soft lockups when running an operation in
kvm_vm_set_mem_attributes() to set memory attributes on the whole
range of guest memory.

watchdog: BUG: soft lockup - CPU#8 stuck for 26s! [qemu-kvm:6372]
CPU: 8 UID: 0 PID: 6372 Comm: qemu-kvm Kdump: loaded Not tainted 6.15.0-rc7.20250520.el9uek.rc1.x86_64 #1 PREEMPT(voluntary)
Hardware name: Oracle Corporation ORACLE SERVER E4-2c/Asm,MB Tray,2U,E4-2c, BIOS 78016600 11/13/2024
RIP: 0010:xas_create+0x78/0x1f0
Code: 00 00 00 41 80 fc 01 0f 84 82 00 00 00 ba 06 00 00 00 bd 06 00 00 00 49 8b 45 08 4d 8d 65 08 41 39 d6 73 20 83 ed 06 48 85 c0 <74> 67 48 89 c2 83 e2 03 48 83 fa 02 75 0c 48 3d 00 10 00 00 0f 87
RSP: 0018:ffffad890a34b940 EFLAGS: 00000286
RAX: ffff96f30b261daa RBX: ffffad890a34b9c8 RCX: 0000000000000000
RDX: 000000000000001e RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000018 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffffad890a356868
R13: ffffad890a356860 R14: 0000000000000000 R15: ffffad890a356868
FS:  00007f5578a2a400(0000) GS:ffff97ed317e1000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f015c70fb18 CR3: 00000001109fd006 CR4: 0000000000f70ef0
PKRU: 55555554
Call Trace:
 <TASK>
 xas_store+0x58/0x630
 __xa_store+0xa5/0x130
 xa_store+0x2c/0x50
 kvm_vm_set_mem_attributes+0x343/0x710 [kvm]
 kvm_vm_ioctl+0x796/0xab0 [kvm]
 __x64_sys_ioctl+0xa3/0xd0
 do_syscall_64+0x8c/0x7a0
 entry_SYSCALL_64_after_hwframe+0x76/0x7e
RIP: 0033:0x7f5578d031bb
Code: ff ff ff 85 c0 79 9b 49 c7 c4 ff ff ff ff 5b 5d 4c 89 e0 41 5c c3 66 0f 1f 84 00 00 00 00 00 f3 0f 1e fa b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 2d 4c 0f 00 f7 d8 64 89 01 48
RSP: 002b:00007ffe0a742b88 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 000000004020aed2 RCX: 00007f5578d031bb
RDX: 00007ffe0a742c80 RSI: 000000004020aed2 RDI: 000000000000000b
RBP: 0000010000000000 R08: 0000010000000000 R09: 0000017680000000
R10: 0000000000000080 R11: 0000000000000246 R12: 00005575e5f95120
R13: 00007ffe0a742c80 R14: 0000000000000008 R15: 00005575e5f961e0

While looping through the range of memory setting the attributes,
call cond_resched() to give the scheduler a chance to run a higher
priority task on the runqueue if necessary and avoid staying in
kernel mode long enough to trigger the lockup.

Fixes: 5a475554db ("KVM: Introduce per-page memory attributes")
Cc: stable@vger.kernel.org # 6.12.x
Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Liam Merwick <liam.merwick@oracle.com>
Reviewed-by: Pankaj Gupta <pankaj.gupta@amd.com>
Link: https://lore.kernel.org/r/20250609091121.2497429-2-liam.merwick@oracle.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
2025-06-24 12:20:17 -07:00
arch KVM: x86/xen: Allow 'out of range' event channel ports in IRQ routing table. 2025-06-24 12:20:17 -07:00
block block-6.16-20250614 2025-06-14 09:25:22 -07:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: hkdf - move to late_initcall 2025-06-11 10:59:45 +08:00
Documentation KVM: TDX: Report supported optional TDVMCALLs in TDX capabilities 2025-06-20 14:20:20 -04:00
drivers IOMMU Fix for Linux v6.16-rc1: 2025-06-14 10:01:47 -07:00
fs three smb3 client fixes 2025-06-14 10:13:32 -07:00
include KVM: TDX: Exit to userspace for SetupEventNotifyInterrupt 2025-06-20 14:09:50 -04:00
init init: fix build warnings about export.h 2025-06-11 22:42:36 -07:00
io_uring io_uring-6.16-20250614 2025-06-14 08:44:54 -07:00
ipc - The 3 patch series "hung_task: extend blocking task stacktrace dump to 2025-05-31 19:12:53 -07:00
kernel posix-cpu-timers: fix race between handle_posix_cpu_timers() and posix_cpu_timer_del() 2025-06-13 10:55:49 -07:00
lib scatterlist: fix extraneous '@'-sign kernel-doc notation 2025-06-11 22:42:35 -07:00
LICENSES LICENSES: add CC0-1.0 license text 2025-05-21 14:54:17 +02:00
mm 9 hotfixes. 3 are cc:stable and the remainder address post-6.15 issues 2025-06-14 08:18:09 -07:00
net Including fixes from bluetooth and wireless. 2025-06-12 09:50:36 -07:00
rust Rust fixes for v6.16 2025-06-14 08:38:34 -07:00
samples - The 3 patch series "hung_task: extend blocking task stacktrace dump to 2025-05-31 19:12:53 -07:00
scripts gendwarfksyms: Fix structure type overrides 2025-06-16 00:49:48 +09:00
security KEYS: Invert FINAL_PUT bit 2025-06-11 11:57:14 -07:00
sound treewide, timers: Rename from_timer() to timer_container_of() 2025-06-08 09:07:37 +02:00
tools KVM: arm64: selftests: Close the GIC FD in arch_timer_edge_cases 2025-06-19 09:58:21 +01:00
usr usr/include: openrisc: don't HDRTEST bpf_perf_event.h 2025-05-12 15:03:17 +09:00
virt KVM: Allow CPU to reschedule while setting per-page memory attributes 2025-06-24 12:20:17 -07:00
.clang-format Linux 6.15-rc5 2025-05-06 16:39:25 +10:00
.clippy.toml rust: clean Rust 1.88.0's warning about clippy::disallowed_macros configuration 2025-05-07 00:11:47 +02:00
.cocciconfig
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore MAINTAINERS: Retire Ralf Baechle 2024-11-12 15:48:59 +01:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore .gitignore: ignore Python compiled bytecode 2025-04-24 10:12:46 -06:00
.mailmap Including fixes from bluetooth and wireless. 2025-06-12 09:50:36 -07:00
.pylintrc docs: add a .pylintrc file with sys path for docs scripts 2025-04-09 12:10:33 -06:00
.rustfmt.toml
COPYING
CREDITS Update Christoph's Email address and make it consistent 2025-05-12 23:50:31 -07:00
Kbuild drm: ensure drm headers are self-contained and pass kernel-doc 2025-02-12 10:44:43 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS 9 hotfixes. 3 are cc:stable and the remainder address post-6.15 issues 2025-06-14 08:18:09 -07:00
Makefile Linux 6.16-rc2 2025-06-15 13:49:41 -07:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

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.