Zachary:
Will you extend the logic to cover the situation when the guest runs at
higher than the guest rate but the PCPU is over committed. In that case, likely
we can use the time spent when the VCPU is scheduled out to catch up as well.
Of course if the VCPU scheduled out time is not enough to compensate the cycles
caused by fast host TSC (exceeding a threahold), we will eventually have to
fall back to trap and emulation mode.
Thx, Eddie
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of
Zachary Amsden
Sent: 2010年8月20日 16:08
To: [email protected]
Cc: Zachary Amsden; Avi Kivity; Marcelo Tosatti; Glauber Costa; Thomas
Gleixner; John Stultz; [email protected]
Subject: [KVM timekeeping 26/35] Catchup slower TSC to guest rate
Use the catchup code to continue adjusting the TSC when
running at lower than the guest rate
Signed-off-by: Zachary Amsden <[email protected]>
---
arch/x86/kvm/x86.c | 9 ++++++++-
1 files changed, 8 insertions(+), 1 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index a4215d7..086d56a 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1013,8 +1013,11 @@ static int kvm_guest_time_update(struct kvm_vcpu *v)
kvm_x86_ops->adjust_tsc_offset(v, tsc-tsc_timestamp);
}
local_irq_restore(flags);
- if (catchup)
+ if (catchup) {
+ if (this_tsc_khz < v->kvm->arch.virtual_tsc_khz)
+ vcpu->tsc_rebase = 1;
return 0;
+ }
/*
* Time as measured by the TSC may go backwards when resetting the base
@@ -5022,6 +5025,10 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
kvm_guest_exit();
+ /* Running on slower TSC without kvmclock, we must bump TSC */
+ if (vcpu->arch.tsc_rebase)
+ kvm_request_clock_update(vcpu);
+
preempt_enable();
vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
--
1.7.1
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