提交 019960ae 编写于 作者: A Avi Kivity

KVM: VMX: Don't adjust tsc offset forward

Most Intel hosts have a stable tsc, and playing with the offset only
reduces accuracy.  By limiting tsc offset adjustment only to forward updates,
we effectively disable tsc offset adjustment on these hosts.
Signed-off-by: NAvi Kivity <avi@qumranet.com>
上级 b8688d51
......@@ -519,7 +519,7 @@ static void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
u64 phys_addr = __pa(vmx->vmcs);
u64 tsc_this, delta;
u64 tsc_this, delta, new_offset;
if (vcpu->cpu != cpu) {
vcpu_clear(vmx);
......@@ -559,8 +559,11 @@ static void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
* Make sure the time stamp counter is monotonous.
*/
rdtscll(tsc_this);
delta = vcpu->arch.host_tsc - tsc_this;
vmcs_write64(TSC_OFFSET, vmcs_read64(TSC_OFFSET) + delta);
if (tsc_this < vcpu->arch.host_tsc) {
delta = vcpu->arch.host_tsc - tsc_this;
new_offset = vmcs_read64(TSC_OFFSET) + delta;
vmcs_write64(TSC_OFFSET, new_offset);
}
}
}
......
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