From 455f9075f14484f358b3c1d6845b4a438de198a7 Mon Sep 17 00:00:00 2001 From: Daniel J Blueman Date: Fri, 19 Apr 2024 16:51:46 +0800 Subject: [PATCH] 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 Signed-off-by: Thomas Gleixner Reviewed-by: Steffen Persvold Reviewed-by: James Cleverdon Reviewed-by: Dimitri Sivanich Reviewed-by: Prarit Bhargava Link: https://lore.kernel.org/r/20240419085146.175665-1-daniel@quora.org --- arch/x86/kernel/tsc_sync.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/arch/x86/kernel/tsc_sync.c b/arch/x86/kernel/tsc_sync.c index 1123ef3ccf90..4334033658ed 100644 --- a/arch/x86/kernel/tsc_sync.c +++ b/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