From: Thomas Gleixner <tglx@linutronix.de>
To: Wanpeng Li <kernellwp@gmail.com>
Cc: Sean Christopherson <seanjc@google.com>,
Michael Tokarev <mjt@tls.msk.ru>,
"qemu-devel@nongnu.org Developers" <qemu-devel@nongnu.org>,
kvm <kvm@vger.kernel.org>, Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: Commit "x86/kvm: Move context tracking where it belongs" broke guest time accounting
Date: Fri, 09 Apr 2021 11:19:48 +0200 [thread overview]
Message-ID: <871rbj6ci3.ffs@nanos.tec.linutronix.de> (raw)
In-Reply-To: <CANRm+CwgvAPOvCxmuEDb+L5kvjBcpWE03Ps70qpqKntHuPxpaA@mail.gmail.com>
On Fri, Apr 09 2021 at 16:13, Wanpeng Li wrote:
> On Thu, 8 Apr 2021 at 21:19, Thomas Gleixner <tglx@linutronix.de> wrote:
>
> + account_guest_enter();
This wants to move into the instrumentation_begin/end() section above.
> guest_enter_irqoff();
> lockdep_hardirqs_on(CALLER_ADDR0);
>
> @@ -3759,6 +3760,8 @@ static noinstr void svm_vcpu_enter_exit(struct
> kvm_vcpu *vcpu)
> */
> lockdep_hardirqs_off(CALLER_ADDR0);
> guest_exit_irqoff();
> + if (vtime_accounting_enabled_this_cpu())
> + account_guest_exit();
This time below. Aside of that I'd suggest to have two inlines instead
of having the conditional here.
>
> #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
> -/* must be called with irqs disabled */
> -static __always_inline void guest_enter_irqoff(void)
> +static __always_inline void account_guest_enter(void)
> {
> instrumentation_begin();
> if (vtime_accounting_enabled_this_cpu())
> @@ -113,7 +112,11 @@ static __always_inline void guest_enter_irqoff(void)
> else
> current->flags |= PF_VCPU;
> instrumentation_end();
If you move the invocation into the instrumentable section then this
instrumentation_begin/end() can be removed.
Something like the below +/- the obligatory bikeshed painting
vs. function names.
Thanks,
tglx
---
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -3782,6 +3782,7 @@ static noinstr void svm_vcpu_enter_exit(
* accordingly.
*/
instrumentation_begin();
+ vtime_account_guest_enter();
trace_hardirqs_on_prepare();
lockdep_hardirqs_on_prepare(CALLER_ADDR0);
instrumentation_end();
@@ -3816,6 +3817,7 @@ static noinstr void svm_vcpu_enter_exit(
instrumentation_begin();
trace_hardirqs_off_finish();
+ vtime_account_guest_exit();
instrumentation_end();
}
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6655,6 +6655,7 @@ static noinstr void vmx_vcpu_enter_exit(
* accordingly.
*/
instrumentation_begin();
+ vtime_account_guest_enter();
trace_hardirqs_on_prepare();
lockdep_hardirqs_on_prepare(CALLER_ADDR0);
instrumentation_end();
@@ -6693,6 +6694,7 @@ static noinstr void vmx_vcpu_enter_exit(
instrumentation_begin();
trace_hardirqs_off_finish();
+ vtime_account_guest_exit();
instrumentation_end();
}
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9200,6 +9200,7 @@ static int vcpu_enter_guest(struct kvm_v
++vcpu->stat.exits;
local_irq_disable();
kvm_after_interrupt(vcpu);
+ vcpu_account_guest_exit();
if (lapic_in_kernel(vcpu)) {
s64 delta = vcpu->arch.apic->lapic_timer.advance_expire_delta;
--- a/include/linux/context_tracking.h
+++ b/include/linux/context_tracking.h
@@ -107,13 +107,6 @@ static inline void context_tracking_init
/* must be called with irqs disabled */
static __always_inline void guest_enter_irqoff(void)
{
- instrumentation_begin();
- if (vtime_accounting_enabled_this_cpu())
- vtime_guest_enter(current);
- else
- current->flags |= PF_VCPU;
- instrumentation_end();
-
if (context_tracking_enabled())
__context_tracking_enter(CONTEXT_GUEST);
@@ -135,37 +128,18 @@ static __always_inline void guest_exit_i
{
if (context_tracking_enabled())
__context_tracking_exit(CONTEXT_GUEST);
-
- instrumentation_begin();
- if (vtime_accounting_enabled_this_cpu())
- vtime_guest_exit(current);
- else
- current->flags &= ~PF_VCPU;
- instrumentation_end();
}
#else
static __always_inline void guest_enter_irqoff(void)
{
- /*
- * This is running in ioctl context so its safe
- * to assume that it's the stime pending cputime
- * to flush.
- */
instrumentation_begin();
- vtime_account_kernel(current);
- current->flags |= PF_VCPU;
rcu_virt_note_context_switch(smp_processor_id());
instrumentation_end();
}
static __always_inline void guest_exit_irqoff(void)
{
- instrumentation_begin();
- /* Flush the guest cputime we spent on the guest */
- vtime_account_kernel(current);
- current->flags &= ~PF_VCPU;
- instrumentation_end();
}
#endif /* CONFIG_VIRT_CPU_ACCOUNTING_GEN */
@@ -178,4 +152,24 @@ static inline void guest_exit(void)
local_irq_restore(flags);
}
+static __always_inline void vtime_account_guest_enter(void)
+{
+ if (vtime_accounting_enabled_this_cpu())
+ vtime_guest_enter(current);
+ else
+ current->flags |= PF_VCPU;
+}
+
+static __always_inline void vtime_account_guest_exit(void)
+{
+ if (vtime_accounting_enabled_this_cpu())
+ vtime_guest_exit(current);
+}
+
+static __always_inline void vcpu_account_guest_exit(void)
+{
+ if (!vtime_accounting_enabled_this_cpu())
+ current->flags &= ~PF_VCPU;
+}
+
#endif
next prev parent reply other threads:[~2021-04-09 9:21 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-06 20:17 Commit "x86/kvm: Move context tracking where it belongs" broke guest time accounting Michael Tokarev
2021-04-06 21:47 ` Sean Christopherson
2021-04-08 13:18 ` Thomas Gleixner
2021-04-09 2:14 ` Wanpeng Li
2021-04-09 8:13 ` Wanpeng Li
2021-04-09 9:19 ` Thomas Gleixner [this message]
2021-04-07 11:01 ` Wanpeng Li
2021-04-13 10:48 ` Wanpeng Li
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