From: Sean Christopherson <seanjc@google.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>,
Christian Borntraeger <borntraeger@de.ibm.com>,
Michael Tokarev <mjt@tls.msk.ru>
Subject: [RFC PATCH 7/7] KVM: x86: Defer tick-based accounting 'til after IRQ handling
Date: Tue, 13 Apr 2021 11:29:33 -0700 [thread overview]
Message-ID: <20210413182933.1046389-8-seanjc@google.com> (raw)
In-Reply-To: <20210413182933.1046389-1-seanjc@google.com>
When using tick-based accounting, defer the call to account guest time
until after servicing any IRQ(s) that happened in the guest (or
immediately after VM-Exit). When using tick-based accounting, time is
accounted to the guest when PF_VCPU is set when the tick IRQ handler
runs. The current approach of unconditionally accounting time in
kvm_guest_exit_irqoff() prevents IRQs that occur in the guest from ever
being processed with PF_VCPU set, since PF_VCPU ends up being set only
during the relatively short VM-Enter sequence, which runs entirely with
IRQs disabled.
Fixes: 87fa7f3e98a131 ("x86/kvm: Move context tracking where it belongs")
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Michael Tokarev <mjt@tls.msk.ru>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/x86.c | 8 ++++++++
arch/x86/kvm/x86.h | 9 ++++++---
2 files changed, 14 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 16fb39503296..096bbf50b7a9 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9230,6 +9230,14 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
local_irq_disable();
kvm_after_interrupt(vcpu);
+ /*
+ * When using tick-based account, 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.
+ */
+ if (!IS_ENABLED(CONFIG_VIRT_CPU_ACCOUNTING_GEN))
+ kvm_vtime_account_guest_exit();
+
if (lapic_in_kernel(vcpu)) {
s64 delta = vcpu->arch.apic->lapic_timer.advance_expire_delta;
if (delta != S64_MIN) {
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index 74ef92f47db8..039a7d585925 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -38,15 +38,18 @@ static __always_inline void kvm_guest_exit_irqoff(void)
* 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_irqoff() 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_irqoff();
+
+ if (IS_ENABLED(CONFIG_VIRT_CPU_ACCOUNTING_GEN))
+ kvm_vtime_account_guest_exit();
instrumentation_begin();
trace_hardirqs_off_finish();
--
2.31.1.295.g9ea45b61b8-goog
next prev parent reply other threads:[~2021-04-13 18:30 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-13 18:29 [RFC PATCH 0/7] KVM: Fix tick-based vtime accounting on x86 Sean Christopherson
2021-04-13 18:29 ` [RFC PATCH 1/7] sched/vtime: Move guest enter/exit vtime accounting to separate helpers Sean Christopherson
2021-04-13 18:29 ` [RFC PATCH 2/7] context_tracking: Move guest enter/exit logic to standalone helpers Sean Christopherson
2021-04-13 18:29 ` [RFC PATCH 3/7] context_tracking: Consolidate guest enter/exit wrappers Sean Christopherson
2021-04-13 18:29 ` [RFC PATCH 4/7] context_tracking: KVM: Move guest enter/exit wrappers to KVM's domain Sean Christopherson
2021-04-13 18:29 ` [RFC PATCH 5/7] KVM: Move vtime accounting of guest exit to separate helper Sean Christopherson
2021-04-13 18:29 ` [RFC PATCH 6/7] KVM: x86: Consolidate guest enter/exit logic to common helpers Sean Christopherson
2021-04-13 18:29 ` Sean Christopherson [this message]
2021-04-14 17:33 ` [RFC PATCH 0/7] KVM: Fix tick-based vtime accounting on x86 Thomas Gleixner
2021-04-14 17:57 ` Sean Christopherson
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