On Thu, 02 May 2024 14:39:36 -0700, Zide Chen wrote:
> Currently, the migration worker delays 1-10 us, assuming that one
> KVM_RUN iteration only takes a few microseconds. But if the CPU low
> power wakeup latency is large enough, for example, hundreds or even
> thousands of microseconds deep C-state exit latencies on x86 server
> CPUs, it may happen that it's not able to wakeup the target CPU before
> the migration worker starts to migrate the vCPU thread to the next CPU.
>
> [...]
Applied to kvm-x86 selftests, thanks! I tweaked the changelog slightly to call
out the new comment and assert message. I also added an extra newline so that
the "help" part of the assert message is isolated from the primary explanation
of why the assert fired. E.g. the output looks like:
==== Test Assertion Failure ====
rseq_test.c:290: skip_sanity_check || i > (NR_TASK_MIGRATIONS * 2002)
pid=20283 tid=20283 errno=4 - Interrupted system call
1 0x000000000040210a: main at rseq_test.c:286
2 0x00007f07fa821c86: ?? ??:0
3 0x0000000000402209: _start at ??:?
Only performed 11162 KVM_RUNs, task stalled too much?
Try disabling deep sleep states to reduce CPU wakeup latency,
e.g. via cpuidle.off=1 or setting /dev/cpu_dma_latency to '0',
or run with -u to disable this sanity check.
[1/1] KVM: selftests: Add a new option to rseq_test
https://github.com/kvm-x86/linux/commit/20ecf595b513
--
https://github.com/kvm-x86/linux/tree/next
