From: Sean Christopherson <[email protected]> Sent: Wednesday, July 1, 2026 12:32 PM > > Add dedicated hypervisor hooks for getting known TSC/CPU frequencies > instead of overriding seemingly generic platform hooks, and explicitly > priotize hypervisor-provided frequencies over native methods, but do NOT
s/priotize/prioritize/ > clobber the frequency obtained from trusted firmware. While shuffling the > hooks around is arguably "six of one, half dozen of the other", scoping > them to x86_hyper_init makes their purpose more obvious, and allows for > explicitly defining the priority of sources (as is done here). > > As is already done when trusted firmware provides the TSC frequency, ignore Word "ignore" is duplicated. > ignore tsc_early_khz if the exact TSC frequency was obtained from the > hypervisor, as attempting to refine the TSC frequency when running in a VM > is all but guaranteed to cause problems sooner or later due to the > calibration sources being emulated devices in the vast majority of setups. > > Cc: David Woodhouse <[email protected]> > Signed-off-by: Sean Christopherson <[email protected]> For the Hyper-V changes, Reviewed-by: Michael Kelley <[email protected]> > --- > .../admin-guide/kernel-parameters.txt | 3 +- > arch/x86/include/asm/acrn.h | 5 ---- > arch/x86/include/asm/x86_init.h | 4 +++ > arch/x86/kernel/cpu/acrn.c | 10 +++++-- > arch/x86/kernel/cpu/mshyperv.c | 6 ++-- > arch/x86/kernel/cpu/vmware.c | 8 ++--- > arch/x86/kernel/jailhouse.c | 6 ++-- > arch/x86/kernel/kvmclock.c | 6 ++-- > arch/x86/kernel/tsc.c | 29 ++++++++++++++----- > arch/x86/xen/time.c | 4 +-- > 10 files changed, 50 insertions(+), 31 deletions(-) > > diff --git a/Documentation/admin-guide/kernel-parameters.txt > b/Documentation/admin- > guide/kernel-parameters.txt > index 490e6aa72fc2..a387bb2c47e2 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -7948,7 +7948,8 @@ Kernel parameters > > Note, tsc_early_khz is ignored if the TSC frequency is > provided by trusted firmware when running as an SNP or > - TDX guest. > + TDX guest, or when the hypervisor provides the exact > + frequency via a paravirtual interface. > > tsx= [X86] Control Transactional Synchronization > Extensions (TSX) feature in Intel processors that > diff --git a/arch/x86/include/asm/acrn.h b/arch/x86/include/asm/acrn.h > index db42b477c41d..a892179c61c6 100644 > --- a/arch/x86/include/asm/acrn.h > +++ b/arch/x86/include/asm/acrn.h > @@ -32,11 +32,6 @@ static inline u32 acrn_cpuid_base(void) > return 0; > } > > -static inline unsigned long acrn_get_tsc_khz(void) > -{ > - return cpuid_eax(ACRN_CPUID_TIMING_INFO); > -} > - > /* > * Hypercalls for ACRN > * > diff --git a/arch/x86/include/asm/x86_init.h b/arch/x86/include/asm/x86_init.h > index 953d3199408a..0c89bf40f507 100644 > --- a/arch/x86/include/asm/x86_init.h > +++ b/arch/x86/include/asm/x86_init.h > @@ -123,6 +123,8 @@ struct x86_init_pci { > * @msi_ext_dest_id: MSI supports 15-bit APIC IDs > * @init_mem_mapping: setup early mappings during > init_mem_mapping() > * @init_after_bootmem: guest init after boot allocator is > finished > + * @get_tsc_khz: get the TSC frequency (returns 0 if frequency > is unknown) > + * @get_cpu_khz: get the CPU frequency (returns 0 if frequency > is unknown) > */ > struct x86_hyper_init { > void (*init_platform)(void); > @@ -131,6 +133,8 @@ struct x86_hyper_init { > bool (*msi_ext_dest_id)(void); > void (*init_mem_mapping)(void); > void (*init_after_bootmem)(void); > + unsigned int (*get_tsc_khz)(void); > + unsigned int (*get_cpu_khz)(void); > }; > > /** > diff --git a/arch/x86/kernel/cpu/acrn.c b/arch/x86/kernel/cpu/acrn.c > index dc119af83524..ad8f2da8003b 100644 > --- a/arch/x86/kernel/cpu/acrn.c > +++ b/arch/x86/kernel/cpu/acrn.c > @@ -24,13 +24,15 @@ static u32 __init acrn_detect(void) > return acrn_cpuid_base(); > } > > +static unsigned int __init acrn_get_tsc_khz(void) > +{ > + return cpuid_eax(ACRN_CPUID_TIMING_INFO); > +} > + > static void __init acrn_init_platform(void) > { > /* Install system interrupt handler for ACRN hypervisor callback */ > sysvec_install(HYPERVISOR_CALLBACK_VECTOR, sysvec_acrn_hv_callback); > - > - x86_platform.calibrate_tsc = acrn_get_tsc_khz; > - x86_platform.calibrate_cpu = acrn_get_tsc_khz; > } > > static bool acrn_x2apic_available(void) > @@ -78,4 +80,6 @@ const __initconst struct hypervisor_x86 x86_hyper_acrn = { > .type = X86_HYPER_ACRN, > .init.init_platform = acrn_init_platform, > .init.x2apic_available = acrn_x2apic_available, > + .init.get_tsc_khz = acrn_get_tsc_khz, > + .init.get_cpu_khz = acrn_get_tsc_khz, > }; > diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c > index 87beecec76f0..f9bc1c2d8c93 100644 > --- a/arch/x86/kernel/cpu/mshyperv.c > +++ b/arch/x86/kernel/cpu/mshyperv.c > @@ -395,7 +395,7 @@ static int hv_nmi_unknown(unsigned int val, struct > pt_regs *regs) > } > #endif > > -static unsigned long hv_get_tsc_khz(void) > +static unsigned int __init hv_get_tsc_khz(void) > { > unsigned long freq; > > @@ -573,8 +573,8 @@ static void __init ms_hyperv_init_platform(void) > > if (ms_hyperv.features & HV_ACCESS_FREQUENCY_MSRS && > ms_hyperv.misc_features & HV_FEATURE_FREQUENCY_MSRS_AVAILABLE) { > - x86_platform.calibrate_tsc = hv_get_tsc_khz; > - x86_platform.calibrate_cpu = hv_get_tsc_khz; > + 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); > } > > diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c > index 13b97265c535..3cb473cae462 100644 > --- a/arch/x86/kernel/cpu/vmware.c > +++ b/arch/x86/kernel/cpu/vmware.c > @@ -64,7 +64,7 @@ struct vmware_steal_time { > u64 reserved[7]; > }; > > -static unsigned long vmware_tsc_khz __ro_after_init; > +static unsigned long vmware_tsc_khz __initdata; > static u8 vmware_hypercall_mode __ro_after_init; > > unsigned long vmware_hypercall_slow(unsigned long cmd, > @@ -137,7 +137,7 @@ static inline int __vmware_platform(void) > return eax != UINT_MAX && ebx == VMWARE_HYPERVISOR_MAGIC; > } > > -static unsigned long vmware_get_tsc_khz(void) > +static unsigned int __init vmware_get_tsc_khz(void) > { > return vmware_tsc_khz; > } > @@ -419,8 +419,8 @@ static void __init vmware_platform_setup(void) > } > > vmware_tsc_khz = tsc_khz; > - x86_platform.calibrate_tsc = vmware_get_tsc_khz; > - x86_platform.calibrate_cpu = vmware_get_tsc_khz; > + x86_init.hyper.get_tsc_khz = vmware_get_tsc_khz; > + x86_init.hyper.get_cpu_khz = vmware_get_tsc_khz; > > /* Skip lapic calibration since we know the bus frequency. */ > apic_set_timer_period_hz(ecx, "VMware hypervisor"); > diff --git a/arch/x86/kernel/jailhouse.c b/arch/x86/kernel/jailhouse.c > index f2d4ef89c085..e24c05ab4fae 100644 > --- a/arch/x86/kernel/jailhouse.c > +++ b/arch/x86/kernel/jailhouse.c > @@ -68,7 +68,7 @@ static void __init jailhouse_timer_init(void) > apic_set_timer_period_khz(setup_data.v1.apic_khz, "Jailhouse > hypervisor"); > } > > -static unsigned long jailhouse_get_tsc(void) > +static unsigned int __init jailhouse_get_tsc(void) > { > return precalibrated_tsc_khz; > } > @@ -210,8 +210,6 @@ static void __init jailhouse_init_platform(void) > x86_init.mpparse.parse_smp_cfg = jailhouse_parse_smp_config; > x86_init.pci.arch_init = jailhouse_pci_arch_init; > > - x86_platform.calibrate_cpu = jailhouse_get_tsc; > - x86_platform.calibrate_tsc = jailhouse_get_tsc; > x86_platform.get_wallclock = jailhouse_get_wallclock; > x86_platform.legacy.rtc = 0; > x86_platform.legacy.warm_reset = 0; > @@ -293,5 +291,7 @@ const struct hypervisor_x86 x86_hyper_jailhouse > __refconst = { > .detect = jailhouse_detect, > .init.init_platform = jailhouse_init_platform, > .init.x2apic_available = jailhouse_x2apic_available, > + .init.get_tsc_khz = jailhouse_get_tsc, > + .init.get_cpu_khz = jailhouse_get_tsc, > .ignore_nopv = true, > }; > diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c > index cb3d0ca1fa22..4f8299303a19 100644 > --- a/arch/x86/kernel/kvmclock.c > +++ b/arch/x86/kernel/kvmclock.c > @@ -136,7 +136,7 @@ static inline void kvm_sched_clock_init(bool stable) > * poll of guests can be running and trouble each other. So we preset > * lpj here > */ > -static unsigned long kvm_get_tsc_khz(void) > +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()); > @@ -343,8 +343,8 @@ void __init kvmclock_init(void) > flags = pvclock_read_flags(&hv_clock_boot[0].pvti); > kvm_sched_clock_init(flags & PVCLOCK_TSC_STABLE_BIT); > > - x86_platform.calibrate_tsc = kvm_get_tsc_khz; > - x86_platform.calibrate_cpu = kvm_get_tsc_khz; > + x86_init.hyper.get_tsc_khz = kvm_get_tsc_khz; > + x86_init.hyper.get_cpu_khz = kvm_get_tsc_khz; > x86_platform.get_wallclock = kvm_get_wallclock; > x86_platform.set_wallclock = kvm_set_wallclock; > #ifdef CONFIG_X86_LOCAL_APIC > diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c > index 86384a83a5f6..1dca9464b41c 100644 > --- a/arch/x86/kernel/tsc.c > +++ b/arch/x86/kernel/tsc.c > @@ -1451,13 +1451,17 @@ static int __init init_tsc_clocksource(void) > device_initcall(init_tsc_clocksource); > > static bool __init determine_cpu_tsc_frequencies(bool early, > + unsigned int known_cpu_khz, > unsigned int known_tsc_khz) > { > /* Make sure that cpu and tsc are not already calibrated */ > WARN_ON(cpu_khz || tsc_khz); > > if (early) { > - cpu_khz = x86_platform.calibrate_cpu(); > + if (known_cpu_khz) > + cpu_khz = known_cpu_khz; > + else > + cpu_khz = x86_platform.calibrate_cpu(); > if (known_tsc_khz) > tsc_khz = known_tsc_khz; > else > @@ -1514,7 +1518,7 @@ static void __init tsc_enable_sched_clock(void) > > void __init tsc_early_init(void) > { > - unsigned int known_tsc_khz = 0; > + unsigned int known_cpu_khz = 0, known_tsc_khz = 0; > > if (!boot_cpu_has(X86_FEATURE_TSC)) > return; > @@ -1522,22 +1526,33 @@ void __init tsc_early_init(void) > if (is_early_uv_system()) > return; > > + if (x86_init.hyper.get_cpu_khz) > + known_cpu_khz = x86_init.hyper.get_cpu_khz(); > + > if (cc_platform_has(CC_ATTR_GUEST_SNP_SECURE_TSC)) > known_tsc_khz = snp_secure_tsc_init(); > else if (boot_cpu_has(X86_FEATURE_TDX_GUEST)) > known_tsc_khz = tdx_tsc_init(); > > + /* > + * If the TSC frequency wasn't provided by trusted firmware, try to get > + * it from the hypervisor (which is untrusted when running as a CoCo > guest). > + */ > + if (!known_tsc_khz && x86_init.hyper.get_tsc_khz) > + known_tsc_khz = x86_init.hyper.get_tsc_khz(); > + > /* > * Ignore the user-provided TSC frequency if the exact frequency was > - * obtained from trusted firmware, as the user-provided frequency is > - * intended as a "starting point", not a known, guaranteed frequency. > + * obtained from trusted firmware or the hypervisor, 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; > else if (tsc_early_khz) > - pr_err("Ignoring 'tsc_early_khz' in favor of trusted > firmware.\n"); > + pr_err("Ignoring 'tsc_early_khz' in favor of > firmware/hypervisor.\n"); > > - if (!determine_cpu_tsc_frequencies(true, known_tsc_khz)) > + if (!determine_cpu_tsc_frequencies(true, known_cpu_khz, known_tsc_khz)) > return; > tsc_enable_sched_clock(); > } > @@ -1558,7 +1573,7 @@ void __init tsc_init(void) > > if (!tsc_khz) { > /* We failed to determine frequencies earlier, try again */ > - if (!determine_cpu_tsc_frequencies(false, 0)) { > + if (!determine_cpu_tsc_frequencies(false, 0, 0)) { > mark_tsc_unstable("could not calculate TSC khz"); > setup_clear_cpu_cap(X86_FEATURE_TSC_DEADLINE_TIMER); > return; > diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c > index d62c14334b35..1adb44fdddb2 100644 > --- a/arch/x86/xen/time.c > +++ b/arch/x86/xen/time.c > @@ -38,7 +38,7 @@ > static u64 xen_sched_clock_offset __read_mostly; > > /* Get the TSC speed from Xen */ > -static unsigned long xen_tsc_khz(void) > +static unsigned int __init xen_tsc_khz(void) > { > struct pvclock_vcpu_time_info *info = > &HYPERVISOR_shared_info->vcpu_info[0].time; > @@ -569,7 +569,7 @@ static void __init xen_init_time_common(void) > static_call_update(pv_steal_clock, xen_steal_clock); > paravirt_set_sched_clock(xen_sched_clock); > > - x86_platform.calibrate_tsc = xen_tsc_khz; > + x86_init.hyper.get_tsc_khz = xen_tsc_khz; > x86_platform.get_wallclock = xen_get_wallclock; > } > > -- > 2.55.0.rc0.799.gd6f94ed593-goog >
