From: "tip-bot2 for Wanpeng Li" <tip-bot2@linutronix.de>
To: linux-tip-commits@vger.kernel.org
Cc: Thomas Gleixner <tglx@linutronix.de>,
Wanpeng Li <wanpengli@tencent.com>,
Sean Christopherson <seanjc@google.com>,
stable@vger.kernel.org, x86@kernel.org,
linux-kernel@vger.kernel.org
Subject: [tip: x86/urgent] KVM: x86: Defer vtime accounting 'til after IRQ handling
Date: Thu, 06 May 2021 12:14:04 -0000 [thread overview]
Message-ID: <162030324464.29796.14687279478344934242.tip-bot2@tip-bot2> (raw)
In-Reply-To: <20210505002735.1684165-4-seanjc@google.com>
The following commit has been merged into the x86/urgent branch of tip:
Commit-ID: 160457140187c5fb127b844e5a85f87f00a01b14
Gitweb: https://git.kernel.org/tip/160457140187c5fb127b844e5a85f87f00a01b14
Author: Wanpeng Li <wanpengli@tencent.com>
AuthorDate: Tue, 04 May 2021 17:27:30 -07:00
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Wed, 05 May 2021 22:54:11 +02:00
KVM: x86: Defer vtime accounting 'til after IRQ handling
Defer the call to account guest time until after servicing any IRQ(s)
that happened in the guest or immediately after VM-Exit. Tick-based
accounting of vCPU time relies on PF_VCPU being set when the tick IRQ
handler runs, and IRQs are blocked throughout the main sequence of
vcpu_enter_guest(), including the call into vendor code to actually
enter and exit the guest.
This fixes a bug where reported guest time remains '0', even when
running an infinite loop in the guest:
https://bugzilla.kernel.org/show_bug.cgi?id=209831
Fixes: 87fa7f3e98a131 ("x86/kvm: Move context tracking where it belongs")
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20210505002735.1684165-4-seanjc@google.com
---
arch/x86/kvm/svm/svm.c | 6 +++---
arch/x86/kvm/vmx/vmx.c | 6 +++---
arch/x86/kvm/x86.c | 9 +++++++++
3 files changed, 15 insertions(+), 6 deletions(-)
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 9790c73..c400def 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -3753,15 +3753,15 @@ static noinstr void svm_vcpu_enter_exit(struct kvm_vcpu *vcpu)
* have them in state 'on' as recorded before entering guest mode.
* Same as enter_from_user_mode().
*
- * guest_exit_irqoff() restores host context and reinstates RCU if
- * enabled and required.
+ * context_tracking_guest_exit() restores host context and reinstates
+ * RCU if enabled and required.
*
* This needs to be done before the below as native_read_msr()
* contains a tracepoint and x86_spec_ctrl_restore_host() calls
* into world and some more.
*/
lockdep_hardirqs_off(CALLER_ADDR0);
- guest_exit_irqoff();
+ context_tracking_guest_exit();
instrumentation_begin();
trace_hardirqs_off_finish();
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index b21d751..e108fb4 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6703,15 +6703,15 @@ static noinstr void vmx_vcpu_enter_exit(struct kvm_vcpu *vcpu,
* have them in state 'on' as recorded before entering guest mode.
* Same as enter_from_user_mode().
*
- * guest_exit_irqoff() restores host context and reinstates RCU if
- * enabled and required.
+ * context_tracking_guest_exit() restores host context and reinstates
+ * RCU if enabled and required.
*
* This needs to be done before the below as native_read_msr()
* contains a tracepoint and x86_spec_ctrl_restore_host() calls
* into world and some more.
*/
lockdep_hardirqs_off(CALLER_ADDR0);
- guest_exit_irqoff();
+ context_tracking_guest_exit();
instrumentation_begin();
trace_hardirqs_off_finish();
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index cebdaa1..6eda283 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9315,6 +9315,15 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
local_irq_disable();
kvm_after_interrupt(vcpu);
+ /*
+ * Wait until after servicing IRQs to account guest time so that any
+ * ticks that occurred while running the guest are properly accounted
+ * to the guest. Waiting until IRQs are enabled degrades the accuracy
+ * of accounting via context tracking, but the loss of accuracy is
+ * acceptable for all known use cases.
+ */
+ vtime_account_guest_exit();
+
if (lapic_in_kernel(vcpu)) {
s64 delta = vcpu->arch.apic->lapic_timer.advance_expire_delta;
if (delta != S64_MIN) {
next prev parent reply other threads:[~2021-05-06 12:14 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-05 0:27 [PATCH v4 0/8] KVM: Fix tick-based accounting for x86 guests Sean Christopherson
2021-05-05 0:27 ` [PATCH v4 1/8] context_tracking: Move guest exit context tracking to separate helpers Sean Christopherson
2021-05-06 12:14 ` [tip: x86/urgent] " tip-bot2 for Wanpeng Li
2021-05-05 0:27 ` [PATCH v4 2/8] context_tracking: Move guest exit vtime accounting " Sean Christopherson
2021-05-06 12:14 ` [tip: x86/urgent] " tip-bot2 for Wanpeng Li
2021-05-05 0:27 ` [PATCH v4 3/8] KVM: x86: Defer vtime accounting 'til after IRQ handling Sean Christopherson
2021-05-05 20:14 ` Thomas Gleixner
2021-05-06 12:14 ` tip-bot2 for Wanpeng Li [this message]
2021-05-05 0:27 ` [PATCH v4 4/8] sched/vtime: Move vtime accounting external declarations above inlines Sean Christopherson
2021-05-06 12:14 ` [tip: x86/urgent] " tip-bot2 for Sean Christopherson
2021-05-05 0:27 ` [PATCH v4 5/8] sched/vtime: Move guest enter/exit vtime accounting to vtime.h Sean Christopherson
2021-05-06 12:14 ` [tip: x86/urgent] " tip-bot2 for Sean Christopherson
2021-05-05 0:27 ` [PATCH v4 6/8] context_tracking: Consolidate guest enter/exit wrappers Sean Christopherson
2021-05-06 12:14 ` [tip: x86/urgent] " tip-bot2 for Sean Christopherson
2021-05-05 0:27 ` [PATCH v4 7/8] context_tracking: KVM: Move guest enter/exit wrappers to KVM's domain Sean Christopherson
2021-05-06 12:14 ` [tip: x86/urgent] " tip-bot2 for Sean Christopherson
2021-05-05 0:27 ` [PATCH v4 8/8] KVM: x86: Consolidate guest enter/exit logic to common helpers Sean Christopherson
2021-05-06 12:14 ` [tip: x86/urgent] " tip-bot2 for Sean Christopherson
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