Date: Mon, 8 Mar 2021 20:43:48 GMT From: Kyle Evans <kevans@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: 8cc15b0dfc2f - main - x86: tsc: deprioritize TSC on VirtualBox Message-ID: <202103082043.128KhmDL093933@gitrepo.freebsd.org>
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The branch main has been updated by kevans: URL: https://cgit.FreeBSD.org/src/commit/?id=8cc15b0dfc2f3299662e78f18bd6127f83c14ab4 commit 8cc15b0dfc2f3299662e78f18bd6127f83c14ab4 Author: Kyle Evans <kevans@FreeBSD.org> AuthorDate: 2021-03-08 20:20:10 +0000 Commit: Kyle Evans <kevans@FreeBSD.org> CommitDate: 2021-03-08 20:43:06 +0000 x86: tsc: deprioritize TSC on VirtualBox Misbehavior has been observed with TSC under VirtualBox, where threads doing small sleeps (~1 second) may miss their wake up and hang around in a sleep state indefinitely. Switching back to ACPI-fast decidedly fixes it, so stop using TSC on VirtualBox at least for the time being. This partially reverts 84eaf2ccc6aa, applying it only to VirtualBox and increasing the quality to 0. Negative qualities can never be chosen and cannot be chosen with the tunable recently added. If we do not have a timecounter with a higher quality than 0, then TSC does at least leave the system mostly usable. PR: 253087 Reviewed by: emaste, kib MFC after: 3 days Differential Revision: https://reviews.freebsd.org/D29132 --- sys/x86/x86/tsc.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/sys/x86/x86/tsc.c b/sys/x86/x86/tsc.c index de0a1505c2f6..5ffbb64229e9 100644 --- a/sys/x86/x86/tsc.c +++ b/sys/x86/x86/tsc.c @@ -503,6 +503,14 @@ test_tsc(int adj_max_count) if ((!smp_tsc && !tsc_is_invariant)) return (-100); + /* + * Misbehavior of TSC under VirtualBox has been observed. In + * particular, threads doing small (~1 second) sleeps may miss their + * wakeup and hang around in sleep state, causing hangs on shutdown. + */ + if (vm_guest == VM_GUEST_VBOX) + return (0); + size = (mp_maxid + 1) * 3; data = malloc(sizeof(*data) * size * N, M_TEMP, M_WAITOK); adj = 0;
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