x86/tsc: Trust initial offset in architectural TSC-adjust MSRs
JIRA: https://issues.redhat.com/browse/RHEL-29437
Upstream Status: git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git
commit 455f9075f14484f358b3c1d6845b4a438de198a7
Author: Daniel J Blueman daniel@quora.org
Date: Fri Apr 19 16:51:46 2024 +0800
x86/tsc: Trust initial offset in architectural TSC-adjust MSRs
When the BIOS configures the architectural TSC-adjust MSRs on secondary
sockets to correct a constant inter-chassis offset, after Linux brings the
cores online, the TSC sync check later resets the core-local MSR to 0,
triggering HPET fallback and leading to performance loss.
Fix this by unconditionally using the initial adjust values read from the
MSRs. Trusting the initial offsets in this architectural mechanism is a
better approach than special-casing workarounds for specific platforms.
Signed-off-by: Daniel J Blueman <daniel@quora.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Steffen Persvold <sp@numascale.com>
Reviewed-by: James Cleverdon <james.cleverdon.external@eviden.com>
Reviewed-by: Dimitri Sivanich <sivanich@hpe.com>
Reviewed-by: Prarit Bhargava <prarit@redhat.com>
Link: https://lore.kernel.org/r/20240419085146.175665-1-daniel@quora.org
Omitted-fix: 7598293ab37c ("Merge branch into tip/master: 'x86/timers'")
- only a mention of the commit being merged, not a bug or patch
Signed-off-by: Prarit Bhargava prarit@redhat.com