Clean up the setting of PVCLOCK_TSC_STABLE_BIT during kvmclock init to
make it somewhat obvious that pvclock_read_flags() must be called *after*
pvclock_set_flags().
Note, in theory, a different PV clock could have set PVCLOCK_TSC_STABLE_BIT
in the supported flags, i.e. reading flags only if
KVM_FEATURE_CLOCKSOURCE_STABLE_BIT is set could very, very theoretically
result in a change in behavior. In practice, the kernel only supports a
single PV clock.
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
arch/x86/kernel/kvmclock.c | 15 +++++++++++----
1 file changed, 11 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index 934ee4a4c6d4..0580fe1aefa0 100644
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -304,7 +304,7 @@ static void __init kvm_sched_clock_init(bool stable)
void __init kvmclock_init(void)
{
- u8 flags;
+ bool stable = false;
if (!kvm_para_available() || !kvmclock)
return;
@@ -331,11 +331,18 @@ void __init kvmclock_init(void)
kvm_register_clock("primary cpu clock");
pvclock_set_pvti_cpu0_va(hv_clock_boot);
- if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT))
+ if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT)) {
pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT);
- flags = pvclock_read_flags(&hv_clock_boot[0].pvti);
- kvm_sched_clock_init(flags & PVCLOCK_TSC_STABLE_BIT);
+ /*
+ * Check if the clock is stable *after* marking TSC_STABLE as a
+ * valid flag.
+ */
+ stable = pvclock_read_flags(&hv_clock_boot[0].pvti) &
+ PVCLOCK_TSC_STABLE_BIT;
+ }
+
+ kvm_sched_clock_init(stable);
tsc_register_calibration_routines(kvm_get_tsc_khz, kvm_get_tsc_khz);
--
2.48.1.711.g2feabab25a-goog
