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 455f907
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>

Author: prarit

arch/x86/kernel/tsc_sync.c

@@ -193,11 +193,9 @@ bool tsc_store_and_check_tsc_adjust(bool bootcpu)
 	cur->warned = false;
 
 	/*
-	 * If a non-zero TSC value for socket 0 may be valid then the default
-	 * adjusted value cannot assumed to be zero either.
+	 * The default adjust value cannot be assumed to be zero on any socket.
 	 */
-	if (tsc_async_resets)
-		cur->adjusted = bootval;
+	cur->adjusted = bootval;
 
 	/*
 	 * Check whether this CPU is the first in a package to come up. In