From: Wanpeng Li <wanpen...@tencent.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. Tick-based accounting of vCPU time relies on PF_VCPU being set when the tick IRQ handler runs, and IRQs are blocked throughout {svm,vmx}_vcpu_enter_exit().
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") Cc: Thomas Gleixner <t...@linutronix.de> Cc: Sean Christopherson <sea...@google.com> Cc: Michael Tokarev <m...@tls.msk.ru> Cc: sta...@vger.kernel.org#v5.9-rc1+ Suggested-by: Thomas Gleixner <t...@linutronix.de> Signed-off-by: Wanpeng Li <wanpen...@tencent.com> Co-developed-by: Sean Christopherson <sea...@google.com> Signed-off-by: Sean Christopherson <sea...@google.com> --- arch/x86/kvm/svm/svm.c | 13 ++++++++++--- arch/x86/kvm/vmx/vmx.c | 13 ++++++++++--- arch/x86/kvm/x86.c | 8 ++++++++ 3 files changed, 28 insertions(+), 6 deletions(-) diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index 48b396f33bee..bb2aa0dde7c5 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -3750,17 +3750,24 @@ 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_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(); instrumentation_begin(); + /* + * Account guest time when precise accounting based on context tracking + * is enabled. Tick based accounting is deferred until after IRQs that + * occurred within the VM-Enter/VM-Exit "window" are handled. + */ + if (vtime_accounting_enabled_this_cpu()) + vtime_account_guest_exit(); trace_hardirqs_off_finish(); instrumentation_end(); } diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index c05e6e2854b5..5ae9dc197048 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -6639,17 +6639,24 @@ 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_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(); instrumentation_begin(); + /* + * Account guest time when precise accounting based on context tracking + * is enabled. Tick based accounting is deferred until after IRQs that + * occurred within the VM-Enter/VM-Exit "window" are handled. + */ + if (vtime_accounting_enabled_this_cpu()) + vtime_account_guest_exit(); trace_hardirqs_off_finish(); instrumentation_end(); } diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 16fb39503296..e4d475df1d4a 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 accounting, 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 (!vtime_accounting_enabled_this_cpu()) + vtime_account_guest_exit(); + if (lapic_in_kernel(vcpu)) { s64 delta = vcpu->arch.apic->lapic_timer.advance_expire_delta; if (delta != S64_MIN) { -- 2.31.1.368.gbe11c130af-goog