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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2020-03-30 19:35:52 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2020-03-30 19:35:52 -0700 |
| commit | 2853d5fafb1e21707e89aa2e227c90bb2c1ea4a9 (patch) | |
| tree | fc8243bcf4a75902ef843ec65fc06a9d65b187e1 /Documentation | |
| parent | d5f744f9a2ac9ca6d5baf72e97ce6dc4c2f19fe4 (diff) | |
| parent | a6a60741035bb48ca8d9f92a138958818148064c (diff) | |
Merge tag 'x86-splitlock-2020-03-30' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 splitlock updates from Thomas Gleixner:
"Support for 'split lock' detection:
Atomic operations (lock prefixed instructions) which span two cache
lines have to acquire the global bus lock. This is at least 1k cycles
slower than an atomic operation within a cache line and disrupts
performance on other cores. Aside of performance disruption this is a
unpriviledged form of DoS.
Some newer CPUs have the capability to raise an #AC trap when such an
operation is attempted. The detection is by default enabled in warning
mode which will warn once when a user space application is caught. A
command line option allows to disable the detection or to select fatal
mode which will terminate offending applications with SIGBUS"
* tag 'x86-splitlock-2020-03-30' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/split_lock: Avoid runtime reads of the TEST_CTRL MSR
x86/split_lock: Rework the initialization flow of split lock detection
x86/split_lock: Enable split lock detection by kernel
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 9024fb2dc418..cbd8bc7cf21d 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -4711,6 +4711,28 @@ spia_pedr= spia_peddr= + split_lock_detect= + [X86] Enable split lock detection + + When enabled (and if hardware support is present), atomic + instructions that access data across cache line + boundaries will result in an alignment check exception. + + off - not enabled + + warn - the kernel will emit rate limited warnings + about applications triggering the #AC + exception. This mode is the default on CPUs + that supports split lock detection. + + fatal - the kernel will send SIGBUS to applications + that trigger the #AC exception. + + If an #AC exception is hit in the kernel or in + firmware (i.e. not while executing in user mode) + the kernel will oops in either "warn" or "fatal" + mode. + srcutree.counter_wrap_check [KNL] Specifies how frequently to check for grace-period sequence counter wrap for the |