On 29/07/19 13:57, Anup Patel wrote:
> + if (delta_ns > VCPU_TIMER_PROGRAM_THRESHOLD_NS) {
> + hrtimer_start(&t->hrt, ktime_add_ns(ktime_get(), delta_ns),
I think the guest would prefer if you saved the time before enabling
interrupts on the host, and use that here instead of ktime_get().
Otherwise the timer could be delayed arbitrarily by host interrupts.
(Because the RISC-V SBI timer is relative only---which is
unfortunate---guests will already pay a latency price due to the extra
cost of the SBI call compared to a bare metal implementation. Sooner or
later you may want to implement something like x86's heuristic to
advance the timer deadline by a few hundred nanoseconds; perhaps add a
TODO now).
Paolo
> + HRTIMER_MODE_ABS);
> + t->is_set = true;
> + } else
> + kvm_riscv_vcpu_set_interrupt(vcpu, IRQ_S_TIMER);
> +
