Merge: x86/tsc: Trust initial offset in architectural TSC-adjust MSRs

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9/-/merge_requests/4187

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>

Approved-by: Steve Best <sbest@redhat.com>
Approved-by: Lenny Szubowicz <lszubowi@redhat.com>
Approved-by: CKI KWF Bot <cki-ci-bot+kwf-gitlab-com@redhat.com>

Merged-by: Lucas Zampieri <lzampier@redhat.com>

Author: zampierilucas

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