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SubjectRe: [PATCH v7] KVM: LAPIC: Apply change to TDCR right away to the timer
2017-10-06 22:21 GMT+08:00 Paolo Bonzini <pbonzini@redhat.com>:
> On 06/10/2017 16:01, Wanpeng Li wrote:
>> + if (!apic->lapic_timer.period)
>> + return;
>> +
>> + now = ktime_get();
>> + remaining = ktime_sub(apic->lapic_timer.target_expiration, now);
>> + if (ktime_to_ns(remaining) < 0)
>> + remaining = 0;
>> + delta = mod_64(ktime_to_ns(remaining), apic->lapic_timer.period);
>
> I think this shouldn't be happening. If it does, I'm not sure the mod
> is the right thing to do, so I'd just use ktime_to_ns(remaining).
>
> So perhaps let's simplify all this to:
>
> ns_remaining_old = ktime_to_ns(remaining);
> ns_remaining_new = mul_u64_u32_div(ns_remaining_old,
> apic->divide_count, old_divisor);
>
> because below you're calling nsec_to_cycles but remaining is not expressed
> in nanoseconds.
>
>> + if (!delta)
>> + return;
>> +
>> + delta = delta * apic->divide_count / old_divisor;
>> +
>> + limit_periodic_timer_frequency(apic);
>
> This should be done before all the "if"s (which should not be there in v8,
> but you should still call it before "now = ktime_get();").

Just sent out v8 to handle all the comments.

Regards,
Wanpeng Li

>
> Paolo
>
>> + apic->lapic_timer.tscdeadline += nsec_to_cycles(apic->vcpu, delta) -
>> + nsec_to_cycles(apic->vcpu, remaining);
>> + apic->lapic_timer.target_expiration = ktime_add_ns(now, delta);
>> +}
>

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