From: David Woodhouse <dwmw2@infradead.org>
To: kvm@vger.kernel.org
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Jonathan Corbet <corbet@lwn.net>,
Sean Christopherson <seanjc@google.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
Paul Durrant <paul@xen.org>, Shuah Khan <shuah@kernel.org>,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-kselftest@vger.kernel.org,
Oliver Upton <oliver.upton@linux.dev>,
Marcelo Tosatti <mtosatti@redhat.com>,
jalliste@amazon.co.uk, sveith@amazon.de
Subject: [PATCH 08/10] KVM: x86: Remove periodic global clock updates
Date: Thu, 18 Apr 2024 20:34:47 +0100 [thread overview]
Message-ID: <20240418193528.41780-9-dwmw2@infradead.org> (raw)
In-Reply-To: <20240418193528.41780-1-dwmw2@infradead.org>
From: David Woodhouse <dwmw@amazon.co.uk>
This effectively reverts commit 332967a3eac0 ("x86: kvm: introduce
periodic global clock updates"). The periodic update was introduced to
propagate NTP corrections to the guest KVM clock, when the KVM clock was
based on CLOCK_MONOTONIC.
However, commit 53fafdbb8b21 ("KVM: x86: switch KVMCLOCK base to
monotonic raw clock") switched to using CLOCK_MONOTONIC_RAW as the basis
for the KVM clock, avoiding the NTP frequency skew altogether.
So the periodic update serves no purpose. Remove it.
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
---
arch/x86/kvm/x86.c | 25 -------------------------
1 file changed, 25 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 44b3d2a0da5b..4ec4eb850c5b 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -155,9 +155,6 @@ EXPORT_SYMBOL_GPL(report_ignored_msrs);
unsigned int min_timer_period_us = 200;
module_param(min_timer_period_us, uint, 0644);
-static bool __read_mostly kvmclock_periodic_sync = true;
-module_param(kvmclock_periodic_sync, bool, 0444);
-
/* tsc tolerance in parts per million - default to 1/2 of the NTP threshold */
static u32 __read_mostly tsc_tolerance_ppm = 250;
module_param(tsc_tolerance_ppm, uint, 0644);
@@ -3434,20 +3431,6 @@ static void kvm_gen_kvmclock_update(struct kvm_vcpu *v)
KVMCLOCK_UPDATE_DELAY);
}
-#define KVMCLOCK_SYNC_PERIOD (300 * HZ)
-
-static void kvmclock_sync_fn(struct work_struct *work)
-{
- struct delayed_work *dwork = to_delayed_work(work);
- struct kvm_arch *ka = container_of(dwork, struct kvm_arch,
- kvmclock_sync_work);
- struct kvm *kvm = container_of(ka, struct kvm, arch);
-
- schedule_delayed_work(&kvm->arch.kvmclock_update_work, 0);
- schedule_delayed_work(&kvm->arch.kvmclock_sync_work,
- KVMCLOCK_SYNC_PERIOD);
-}
-
/* These helpers are safe iff @msr is known to be an MCx bank MSR. */
static bool is_mci_control_msr(u32 msr)
{
@@ -12416,8 +12399,6 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
void kvm_arch_vcpu_postcreate(struct kvm_vcpu *vcpu)
{
- struct kvm *kvm = vcpu->kvm;
-
if (mutex_lock_killable(&vcpu->mutex))
return;
vcpu_load(vcpu);
@@ -12428,10 +12409,6 @@ void kvm_arch_vcpu_postcreate(struct kvm_vcpu *vcpu)
vcpu->arch.msr_kvm_poll_control = 1;
mutex_unlock(&vcpu->mutex);
-
- if (kvmclock_periodic_sync && vcpu->vcpu_idx == 0)
- schedule_delayed_work(&kvm->arch.kvmclock_sync_work,
- KVMCLOCK_SYNC_PERIOD);
}
void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)
@@ -12804,7 +12781,6 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
#endif
INIT_DELAYED_WORK(&kvm->arch.kvmclock_update_work, kvmclock_update_fn);
- INIT_DELAYED_WORK(&kvm->arch.kvmclock_sync_work, kvmclock_sync_fn);
kvm_apicv_init(kvm);
kvm_hv_init_vm(kvm);
@@ -12844,7 +12820,6 @@ static void kvm_unload_vcpu_mmus(struct kvm *kvm)
void kvm_arch_sync_events(struct kvm *kvm)
{
- cancel_delayed_work_sync(&kvm->arch.kvmclock_sync_work);
cancel_delayed_work_sync(&kvm->arch.kvmclock_update_work);
kvm_free_pit(kvm);
}
--
2.44.0
next prev parent reply other threads:[~2024-04-18 19:43 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-18 19:34 [RFC PATCH 0/10] Cleaning up the KVM clock mess David Woodhouse
2024-04-18 19:34 ` [PATCH 01/10] KVM: x86/xen: Do not corrupt KVM clock in kvm_xen_shared_info_init() David Woodhouse
2024-04-18 19:34 ` [PATCH 02/10] KVM: x86: Improve accuracy of KVM clock when TSC scaling is in force David Woodhouse
2024-04-19 15:29 ` Paul Durrant
2024-04-22 12:22 ` Paolo Bonzini
2024-04-22 15:39 ` David Woodhouse
2024-04-22 15:54 ` Paolo Bonzini
2024-04-22 16:44 ` David Woodhouse
2024-04-18 19:34 ` [PATCH 03/10] KVM: x86: Add KVM_[GS]ET_CLOCK_GUEST for accurate KVM clock migration David Woodhouse
2024-04-19 15:40 ` Paul Durrant
2024-04-19 15:49 ` David Woodhouse
2024-04-22 14:11 ` Paolo Bonzini
2024-04-22 15:02 ` David Woodhouse
2024-04-18 19:34 ` [PATCH 04/10] KVM: selftests: Add KVM/PV clock selftest to prove timer correction David Woodhouse
2024-04-19 15:44 ` Paul Durrant
2024-04-18 19:34 ` [PATCH 05/10] KVM: x86: Explicitly disable TSC scaling without CONSTANT_TSC David Woodhouse
2024-04-19 15:45 ` Paul Durrant
2024-04-18 19:34 ` [PATCH 06/10] KVM: x86: Add KVM_VCPU_TSC_SCALE and fix the documentation on TSC migration David Woodhouse
2024-04-19 15:49 ` Paul Durrant
2024-04-19 15:53 ` David Woodhouse
2024-04-18 19:34 ` [PATCH 07/10] KVM: x86: Avoid NTP frequency skew for KVM clock on 32-bit host David Woodhouse
2024-04-19 15:53 ` Paul Durrant
2024-04-18 19:34 ` David Woodhouse [this message]
2024-04-19 15:55 ` [PATCH 08/10] KVM: x86: Remove periodic global clock updates Paul Durrant
2024-04-18 19:34 ` [PATCH 09/10] KVM: x86: Kill KVM_REQ_GLOBAL_CLOCK_UPDATE David Woodhouse
2024-04-19 15:57 ` Paul Durrant
2024-04-18 19:34 ` [PATCH 10/10] KVM: x86: Fix KVM clock precision in __get_kvmclock() David Woodhouse
2024-04-19 16:07 ` Paul Durrant
2024-04-19 12:51 ` [PATCH 11/10] KVM: x86: Fix software TSC upscaling in kvm_update_guest_time() David Woodhouse
2024-04-19 12:52 ` [RFC PATCH 0/10] Cleaning up the KVM clock mess David Woodhouse
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