From: "Woodhouse, David" <dwmw@amazon.co.uk>
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Subject: Re: [PATCH v3 36/41] x86/kvmclock: Get local APIC bus frequency from PV CPUID Timing Info
Date: Wed, 20 May 2026 23:55:17 +0000 [thread overview]
Message-ID: <7489ff3cc1ff402bf0ade38272fc52dcbcc75fc1.camel@amazon.co.uk> (raw)
In-Reply-To: <20260515191942.1892718-37-seanjc@google.com>
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On Fri, 2026-05-15 at 12:19 -0700, Sean Christopherson wrote:
> When running as a KVM guest with kvmclock support enabled, stuff the APIC
> timer period/frequency with the local APIC bus frequency reported in
> CPUID.0x40000010.EBX instead of trying to calibrate/guess the frequency.
>
> See Documentation/virt/kvm/x86/cpuid.rst for details.
>
> Signed-off-by: Sean Christopherson <seanjc@google.com>
I still don't much like the way this is done inside kvm_get_tsc_khz().
We also probably ought to be looking for the timing leaf on other
hypervisors including VMware and probably Bhyve too. Should it be done
somewhere else?
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Amazon Development Centre (London) Ltd. Registered in England and Wales with registration number 04543232 with its registered office at 1 Principal Place, Worship Street, London EC2A 2FA, United Kingdom.
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next prev parent reply other threads:[~2026-05-20 23:55 UTC|newest]
Thread overview: 111+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-15 19:19 [PATCH v3 00/41] x86: Try to wrangle PV clocks vs. TSC Sean Christopherson
2026-05-15 19:19 ` [PATCH v3 01/41] x86/tsc: Add a standalone helpers for getting TSC info from CPUID.0x15 Sean Christopherson
2026-05-20 18:59 ` David Woodhouse
2026-05-15 19:19 ` [PATCH v3 02/41] x86/tsc: Add helper to register CPU and TSC freq calibration routines Sean Christopherson
2026-05-18 21:59 ` Woodhouse, David
2026-05-20 17:56 ` Sean Christopherson
2026-05-20 19:04 ` David Woodhouse
2026-05-20 20:44 ` Sean Christopherson
2026-05-20 21:19 ` David Woodhouse
2026-05-20 21:33 ` Sean Christopherson
2026-05-20 21:44 ` David Woodhouse
2026-05-21 20:53 ` Sean Christopherson
2026-05-21 21:01 ` David Woodhouse
2026-05-21 21:17 ` Sean Christopherson
2026-05-21 21:37 ` David Woodhouse
2026-05-15 19:19 ` [PATCH v3 03/41] x86/sev: Mark TSC as reliable when configuring Secure TSC Sean Christopherson
2026-05-20 19:06 ` David Woodhouse
2026-05-15 19:19 ` [PATCH v3 04/41] x86/sev: Move check for SNP Secure TSC support to tsc_early_init() Sean Christopherson
2026-05-20 19:16 ` David Woodhouse
2026-05-15 19:19 ` [PATCH v3 05/41] x86/tdx: Override PV calibration routines with CPUID-based calibration Sean Christopherson
2026-05-20 19:52 ` David Woodhouse
2026-05-15 19:19 ` [PATCH v3 06/41] x86/acrn: Mark TSC frequency as known when using ACRN for calibration Sean Christopherson
2026-05-20 20:01 ` David Woodhouse
2026-05-20 21:02 ` Sean Christopherson
2026-05-15 19:19 ` [PATCH v3 07/41] clocksource: hyper-v: Register sched_clock save/restore iff it's necessary Sean Christopherson
2026-05-20 21:27 ` David Woodhouse
2026-05-27 22:49 ` Wei Liu
2026-05-15 19:19 ` [PATCH v3 08/41] clocksource: hyper-v: Drop wrappers to sched_clock save/restore helpers Sean Christopherson
2026-05-20 21:29 ` David Woodhouse
2026-05-27 22:50 ` Wei Liu
2026-05-15 19:19 ` [PATCH v3 09/41] clocksource: hyper-v: Don't save/restore TSC offset when using HV sched_clock Sean Christopherson
2026-05-20 21:30 ` David Woodhouse
2026-05-27 22:50 ` Wei Liu
2026-05-15 19:19 ` [PATCH v3 10/41] x86/kvmclock: Setup kvmclock for secondary CPUs iff CONFIG_SMP=y Sean Christopherson
2026-05-20 21:45 ` David Woodhouse
2026-05-15 19:19 ` [PATCH v3 11/41] x86/kvm: Don't disable kvmclock on BSP in syscore_suspend() Sean Christopherson
2026-05-20 21:51 ` David Woodhouse
2026-05-15 19:19 ` [PATCH v3 12/41] x86/paravirt: Remove unnecessary PARAVIRT=n stub for paravirt_set_sched_clock() Sean Christopherson
2026-05-20 21:53 ` David Woodhouse
2026-05-15 19:19 ` [PATCH v3 13/41] x86/paravirt: Move handling of unstable PV clocks into paravirt_set_sched_clock() Sean Christopherson
2026-05-20 21:57 ` David Woodhouse
2026-05-15 19:19 ` [PATCH v3 14/41] x86/kvmclock: Move sched_clock save/restore helpers up in kvmclock.c Sean Christopherson
2026-05-20 21:59 ` David Woodhouse
2026-05-15 19:19 ` [PATCH v3 15/41] x86/xen/time: Nullify x86_platform's sched_clock save/restore hooks Sean Christopherson
2026-05-20 22:11 ` David Woodhouse
2026-05-20 22:54 ` David Woodhouse
2026-05-15 19:19 ` [PATCH v3 16/41] x86/vmware: Nullify save/restore hooks when using VMware's sched_clock Sean Christopherson
2026-05-20 22:15 ` David Woodhouse
2026-05-15 19:19 ` [PATCH v3 17/41] x86/tsc: WARN if TSC sched_clock save/restore used with PV sched_clock Sean Christopherson
2026-05-20 22:27 ` David Woodhouse
2026-05-15 19:19 ` [PATCH v3 18/41] x86/paravirt: Pass sched_clock save/restore helpers during registration Sean Christopherson
2026-05-20 22:35 ` Woodhouse, David
2026-05-15 19:19 ` [PATCH v3 19/41] x86/kvmclock: Move kvm_sched_clock_init() down in kvmclock.c Sean Christopherson
2026-05-20 22:39 ` David Woodhouse
2026-05-15 19:19 ` [PATCH v3 20/41] x86/xen/time: Mark xen_setup_vsyscall_time_info() as __init Sean Christopherson
2026-05-20 22:40 ` David Woodhouse
2026-05-15 19:19 ` [PATCH v3 21/41] x86/pvclock: Mark setup helpers and related various as __init/__ro_after_init Sean Christopherson
2026-05-20 22:43 ` Woodhouse, David
2026-05-15 19:19 ` [PATCH v3 22/41] x86/pvclock: WARN if pvclock's valid_flags are overwritten Sean Christopherson
2026-05-20 22:44 ` David Woodhouse
2026-05-15 19:19 ` [PATCH v3 23/41] x86/kvmclock: Refactor handling of PVCLOCK_TSC_STABLE_BIT during kvmclock_init() Sean Christopherson
2026-05-20 22:46 ` David Woodhouse
2026-05-15 19:19 ` [PATCH v3 24/41] timekeeping: Resume clocksources before reading persistent clock Sean Christopherson
2026-05-20 22:52 ` David Woodhouse
2026-05-15 19:19 ` [PATCH v3 25/41] x86/kvmclock: Hook clocksource.suspend/resume when kvmclock isn't sched_clock Sean Christopherson
2026-05-20 23:01 ` David Woodhouse
2026-05-20 23:06 ` David Woodhouse
2026-05-15 19:19 ` [PATCH v3 26/41] x86/kvmclock: WARN if wall clock is read while kvmclock is suspended Sean Christopherson
2026-05-20 23:19 ` David Woodhouse
2026-05-15 19:19 ` [PATCH v3 27/41] x86/kvmclock: Enable kvmclock on APs during onlining if kvmclock isn't sched_clock Sean Christopherson
2026-05-20 23:27 ` David Woodhouse
2026-05-21 12:59 ` Sean Christopherson
2026-05-21 13:10 ` Peter Zijlstra
2026-05-21 13:38 ` Sean Christopherson
2026-05-21 14:13 ` David Woodhouse
2026-05-15 19:19 ` [PATCH v3 28/41] x86/paravirt: Mark __paravirt_set_sched_clock() as __init Sean Christopherson
2026-05-20 23:42 ` David Woodhouse
2026-05-15 19:19 ` [PATCH v3 29/41] x86/paravirt: Plumb a return code into __paravirt_set_sched_clock() Sean Christopherson
2026-05-20 23:44 ` David Woodhouse
2026-05-21 20:35 ` Sean Christopherson
2026-05-15 19:19 ` [PATCH v3 30/41] x86/paravirt: Don't use a PV sched_clock in CoCo guests with trusted TSC Sean Christopherson
2026-05-20 23:45 ` David Woodhouse
2026-05-15 19:19 ` [PATCH v3 31/41] x86/tsc: Pass KNOWN_FREQ and RELIABLE as params to registration Sean Christopherson
2026-05-20 23:49 ` Woodhouse, David
2026-05-15 19:19 ` [PATCH v3 32/41] x86/tsc: Rejects attempts to override TSC calibration with lesser routine Sean Christopherson
2026-05-20 23:50 ` David Woodhouse
2026-05-15 19:19 ` [PATCH v3 33/41] x86/kvmclock: Mark TSC as reliable when it's constant and nonstop Sean Christopherson
2026-05-20 23:51 ` David Woodhouse
2026-05-15 19:19 ` [PATCH v3 34/41] KVM: x86: Officially define CPUID 0x40000010 as PV Timing Info (TSC and Bus) Sean Christopherson
2026-05-15 19:19 ` [PATCH v3 35/41] x86/kvmclock: Obtain TSC frequency from CPUID if present Sean Christopherson
2026-05-15 19:19 ` [PATCH v3 36/41] x86/kvmclock: Get local APIC bus frequency from PV CPUID Timing Info Sean Christopherson
2026-05-20 23:55 ` Woodhouse, David [this message]
2026-05-21 20:34 ` Sean Christopherson
2026-05-15 19:19 ` [PATCH v3 37/41] x86/kvmclock: Use TSC for sched_clock if it's constant and non-stop Sean Christopherson
2026-05-20 23:56 ` David Woodhouse
2026-05-21 9:14 ` Dongli Zhang
2026-05-21 21:01 ` Sean Christopherson
2026-05-15 19:19 ` [PATCH v3 38/41] x86/paravirt: kvmclock: Setup kvmclock early iff it's sched_clock Sean Christopherson
2026-05-20 23:59 ` David Woodhouse
2026-05-15 19:19 ` [PATCH v3 39/41] x86/paravirt: Move using_native_sched_clock() stub into timer.h Sean Christopherson
2026-05-21 0:00 ` David Woodhouse
2026-05-15 19:19 ` [PATCH v3 40/41] x86/tsc: Add standalone helper for getting CPU frequency from CPUID Sean Christopherson
2026-05-16 7:42 ` Paolo Bonzini
2026-05-20 18:50 ` David Woodhouse
2026-05-15 19:19 ` [PATCH v3 41/41] x86/kvmclock: Get CPU base frequency from CPUID when it's available Sean Christopherson
2026-05-20 18:52 ` David Woodhouse
2026-05-20 19:06 ` Sean Christopherson
2026-05-18 21:11 ` [PATCH v3 00/41] x86: Try to wrangle PV clocks vs. TSC Sean Christopherson
2026-05-18 23:38 ` David Woodhouse
2026-05-20 17:59 ` Sean Christopherson
2026-05-20 18:30 ` David Woodhouse
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