[PATCH v5 35/51] x86/tsc: WARN if TSC sched_clock save/restore used with PV sched_clock
From: Sean Christopherson <seanjc@google.com>
Date: 2026-07-01 19:33:10
Also in:
kvm, linux-doc, linux-hyperv, lkml, virtualization, xen-devel
Subsystem:
the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
Now that all PV clocksources override the sched_clock save/restore hooks when overriding sched_clock, WARN if the "default" TSC hooks are invoked when using a PV sched_clock, e.g. to guard against regressions. Reviewed-by: David Woodhouse <redacted> Signed-off-by: Sean Christopherson <seanjc@google.com> --- arch/x86/kernel/tsc.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index a762cb5cec0f..7473dcab4775 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c@@ -947,9 +947,17 @@ EXPORT_SYMBOL_FOR_MODULES(recalibrate_cpu_khz, "p4-clockmod,powernow-k7"); static unsigned long long cyc2ns_suspend; +static __always_inline bool tsc_is_save_restore_needed(void) +{ + if (WARN_ON_ONCE(!using_native_sched_clock())) + return false; + + return static_branch_likely(&__use_tsc) || sched_clock_stable(); +} + void tsc_save_sched_clock_state(void) { - if (!static_branch_likely(&__use_tsc) && !sched_clock_stable()) + if (!tsc_is_save_restore_needed()) return; cyc2ns_suspend = sched_clock();
@@ -969,7 +977,7 @@ void tsc_restore_sched_clock_state(void) unsigned long flags; int cpu; - if (!static_branch_likely(&__use_tsc) && !sched_clock_stable()) + if (!tsc_is_save_restore_needed()) return; local_irq_save(flags);
--
2.55.0.rc0.799.gd6f94ed593-goog