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authorWanpeng Li <wanpengli@tencent.com>2021-05-04 17:27:30 -0700
committerThomas Gleixner <tglx@linutronix.de>2021-05-05 22:54:11 +0200
commit160457140187c5fb127b844e5a85f87f00a01b14 (patch)
treee943d4bde2eb6018d9d92250b7f86cfc1b1abb4f /arch
parent88d8220bbf06dd8045b2ac4be1046290eaa7773a (diff)
downloadlinux-160457140187c5fb127b844e5a85f87f00a01b14.tar.bz2
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
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kvm/svm/svm.c6
-rw-r--r--arch/x86/kvm/vmx/vmx.c6
-rw-r--r--arch/x86/kvm/x86.c9
3 files changed, 15 insertions, 6 deletions
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 9790c73f2a32..c400def6220b 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 b21d751407b5..e108fb47855b 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 cebdaa1e3cf5..6eda2834fc05 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) {