From: Wanpeng Li <wanpengli@xxxxxxxxxxx>
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 <tglx@xxxxxxxxxxxxx>
Cc: Sean Christopherson <seanjc@xxxxxxxxxx>
Cc: Michael Tokarev <mjt@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx#v5.9-rc1+
Suggested-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Wanpeng Li <wanpengli@xxxxxxxxxxx>
Co-developed-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
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
