On 26/05/2016 16:05, Alan Jenkins wrote:
> 1. Against my interests: have you actually confirmed the VMX preemption
> timer is affected by guest TSC scaling?
No, it's not, hence my formula:
host_tsc = ((unsigned __int128)(guest_tsc - tsc_offset)
<< kvm_tsc_scaling_ratio_frac_bits)
/ vcpu->arch.tsc_scaling_ratio;
The idea is that once you have a host TSC deadline, you can use it to
set the preemption timer on vmentry.
> It's not explicit in the SDM. The way it's described for allocating
> timeslices to the guest, IMO it makes more sense if it is not scaled.
>
> 2. Paolo, any chance I could also get away with requiring 64-bit? I.e.
>
> #ifdef CONFIG_X86_64
> #define HAVE_LAPIC_TIMER_ADVANCE 1
> #endif
I wouldn't object.
Paolo
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