On Wed, Mar 09, 2022 at 10:26:51AM +0100, David Woodhouse wrote:
> On Sat, 2019-07-06 at 09:26 +0800, Wanpeng Li wrote:
> > From: Wanpeng Li <wanpengli@xxxxxxxxxxx>
> >
> > Commit 61abdbe0bcc2 ("kvm: x86: make lapic hrtimer pinned") pinned the
> > lapic timer to avoid to wait until the next kvm exit for the guest to
> > see KVM_REQ_PENDING_TIMER set. There is another solution to give a kick
> > after setting the KVM_REQ_PENDING_TIMER bit, make lapic timer unpinned
> > will be used in follow up patches.
> >
> > Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> > Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx>
> > Cc: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
> > Signed-off-by: Wanpeng Li <wanpengli@xxxxxxxxxxx>
> > ---
> > arch/x86/kvm/lapic.c | 8 ++++----
> > arch/x86/kvm/x86.c | 6 +-----
> > 2 files changed, 5 insertions(+), 9 deletions(-)
>
> ...
>
>
> > @@ -2510,7 +2510,7 @@ void __kvm_migrate_apic_timer(struct kvm_vcpu *vcpu)
> >
> > timer = &vcpu->arch.apic->lapic_timer.timer;
> > if (hrtimer_cancel(timer))
> > - hrtimer_start_expires(timer, HRTIMER_MODE_ABS_PINNED);
> > + hrtimer_start_expires(timer, HRTIMER_MODE_ABS);
> > }
> >
> > /*
>
> Wait, in that case why are we even bothering to cancel and restart the
> timer? I thought the whole point of that was to pin it to the *new* CPU
> that this vCPU is running on.
>
> If not, can't we just kill __kvm_migrate_apic_timer() off completely
> not?
Current code looks like this:
void __kvm_migrate_apic_timer(struct kvm_vcpu *vcpu)
{
struct hrtimer *timer;
if (!lapic_in_kernel(vcpu) ||
kvm_can_post_timer_interrupt(vcpu)) <----------
return;
timer = &vcpu->arch.apic->lapic_timer.timer;
if (hrtimer_cancel(timer))
hrtimer_start_expires(timer, HRTIMER_MODE_ABS_HARD);
}
Yeah, should be HRTIMER_MODE_ABS_PINNED AFAICS.
