[PATCH v5 14/51] x86/tsc: Consolidate forcing of X86_FEATURE_TSC_KNOWN_FREQ for PV code
From: Sean Christopherson <seanjc@google.com>
Date: 2026-07-01 19:32:44
Also in:
kvm, linux-coco, linux-doc, linux-hyperv, lkml, xen-devel
Subsystem:
hyper-v/azure core and drivers, jailhouse hypervisor interface, kvm paravirt (kvm/paravirt), the rest, vmware hypervisor interface, x86 architecture (32-bit and 64-bit), xen hypervisor x86 · Maintainers:
"K. Y. Srinivasan", Haiyang Zhang, Wei Liu, Dexuan Cui, Long Li, Jan Kiszka, Paolo Bonzini, Linus Torvalds, Ajay Kaher, Alexey Makhalov, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, Juergen Gross
Now that all paravirt code that explicitly specifies the TSC frequency
also sets X86_FEATURE_TSC_KNOWN_FREQ, replace all of the one-off code
and simply set X86_FEATURE_TSC_KNOWN_FREQ if the TSC frequency is known.
Do NOT force set TSC_KNOWN_FREQ if the "known" TSC frequency was provided
by the user. Per commit bd35c77e32e4 ("x86/tsc: Add tsc_early_khz command
line parameter"), one of the goals of the param is to allow the refined
calibration work "to do meaningful error checking".
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/coco/sev/core.c | 1 -
arch/x86/coco/tdx/tdx.c | 1 -
arch/x86/kernel/cpu/acrn.c | 1 -
arch/x86/kernel/cpu/mshyperv.c | 1 -
arch/x86/kernel/cpu/vmware.c | 2 --
arch/x86/kernel/jailhouse.c | 1 -
arch/x86/kernel/kvmclock.c | 1 -
arch/x86/kernel/tsc.c | 13 ++++++++++---
arch/x86/xen/time.c | 1 -
9 files changed, 10 insertions(+), 12 deletions(-)
diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c
index bc5ae9ef74da..72313b36b6f5 100644
--- a/arch/x86/coco/sev/core.c
+++ b/arch/x86/coco/sev/core.c@@ -2027,7 +2027,6 @@ unsigned int __init snp_secure_tsc_init(void) secrets = (__force struct snp_secrets_page *)mem; - setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ); setup_force_cpu_cap(X86_FEATURE_TSC_RELIABLE); rdmsrq(MSR_AMD64_GUEST_TSC_FREQ, tsc_freq_mhz);
diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
index ae2d35f2ef33..94682aca188b 100644
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c@@ -1205,7 +1205,6 @@ unsigned int __init tdx_tsc_init(void) /* TSC is the only reliable clock in TDX guest */ setup_force_cpu_cap(X86_FEATURE_TSC_RELIABLE); - setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ); return info.crystal_khz * info.numerator / info.denominator; }
diff --git a/arch/x86/kernel/cpu/acrn.c b/arch/x86/kernel/cpu/acrn.c
index 3818f6ae0629..dc71a6fdd461 100644
--- a/arch/x86/kernel/cpu/acrn.c
+++ b/arch/x86/kernel/cpu/acrn.c@@ -40,7 +40,6 @@ static void __init acrn_init_platform(void) if (acrn_tsc_khz_cpuid) { x86_init.hyper.get_tsc_khz = acrn_get_tsc_khz; x86_init.hyper.get_cpu_khz = acrn_get_tsc_khz; - setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ); } }
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index f9bc1c2d8c93..e03c69a4db33 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c@@ -575,7 +575,6 @@ static void __init ms_hyperv_init_platform(void) ms_hyperv.misc_features & HV_FEATURE_FREQUENCY_MSRS_AVAILABLE) { x86_init.hyper.get_tsc_khz = hv_get_tsc_khz; x86_init.hyper.get_cpu_khz = hv_get_tsc_khz; - setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ); } if (ms_hyperv.priv_high & HV_ISOLATION) {
diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c
index 3cb473cae462..0a3bd90576d4 100644
--- a/arch/x86/kernel/cpu/vmware.c
+++ b/arch/x86/kernel/cpu/vmware.c@@ -390,8 +390,6 @@ static void __init vmware_set_capabilities(void) { setup_force_cpu_cap(X86_FEATURE_CONSTANT_TSC); setup_force_cpu_cap(X86_FEATURE_TSC_RELIABLE); - if (vmware_tsc_khz) - setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ); if (vmware_hypercall_mode == CPUID_VMWARE_FEATURES_ECX_VMCALL) setup_force_cpu_cap(X86_FEATURE_VMCALL); else if (vmware_hypercall_mode == CPUID_VMWARE_FEATURES_ECX_VMMCALL)
diff --git a/arch/x86/kernel/jailhouse.c b/arch/x86/kernel/jailhouse.c
index e24c05ab4fae..ff173052cdce 100644
--- a/arch/x86/kernel/jailhouse.c
+++ b/arch/x86/kernel/jailhouse.c@@ -255,7 +255,6 @@ static void __init jailhouse_init_platform(void) pr_debug("Jailhouse: PM-Timer IO Port: %#x\n", pmtmr_ioport); precalibrated_tsc_khz = setup_data.v1.tsc_khz; - setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ); pci_probe = 0;
diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index 4f8299303a19..35a879d33e9e 100644
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c@@ -138,7 +138,6 @@ static inline void kvm_sched_clock_init(bool stable) */ static unsigned int __init kvm_get_tsc_khz(void) { - setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ); return pvclock_tsc_khz(this_cpu_pvti()); }
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 1dca9464b41c..676910292af7 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c@@ -1541,11 +1541,18 @@ void __init tsc_early_init(void) if (!known_tsc_khz && x86_init.hyper.get_tsc_khz) known_tsc_khz = x86_init.hyper.get_tsc_khz(); + /* + * Mark the TSC frequency as known if it was obtained from a hypervisor + * or trusted firmware. + */ + if (known_tsc_khz) + setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ); + /* * Ignore the user-provided TSC frequency if the exact frequency was - * obtained from trusted firmware or the hypervisor, as the user- - * provided frequency is intended as a "starting point", not a known, - * guaranteed frequency. + * obtained from trusted firmware or the hypervisor, and don't mark the + * frequency as known, as the user-provided frequency is intended as a + * "starting point", not a known, guaranteed frequency */ if (!known_tsc_khz) known_tsc_khz = tsc_early_khz;
diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
index 1adb44fdddb2..487ad838c441 100644
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c@@ -43,7 +43,6 @@ static unsigned int __init xen_tsc_khz(void) struct pvclock_vcpu_time_info *info = &HYPERVISOR_shared_info->vcpu_info[0].time; - setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ); return pvclock_tsc_khz(info); }
--
2.55.0.rc0.799.gd6f94ed593-goog