James Morris wrote:
> At http://namei.org/misc/lguest/patches/time/v04/
>
> Just a resync to the latest upstream lguest patch queue, after some fun
> with bare metal bugs and assorted churn.
>
>
>
> - James
>
+void guest_clockevent(struct lguest *lg, const ktime_t __user *u)
+{
+ ktime_t kdelta;
+
+ lgread(lg, &kdelta, (u32)u, sizeof(kdelta));
+
+ if (ktime_to_ns(kdelta) < LG_CLOCK_MIN_DELTA) {
+ if (printk_ratelimit())
+ printk(KERN_DEBUG "%s: guest %u small delta %Ld ns\n",
+ __FUNCTION__, lg->guestid, ktime_to_ns(kdelta));
+
+ /* kick guest timer immediately */
+ set_bit(0, lg->irqs_pending);
+ } else
+ hrtimer_start(&lg->hrt, kdelta, HRTIMER_MODE_REL);
+}
Two things:
1. It's probably better to make this interface specified in absolute
rather than relative time. Asking for a timeout "X ns from _now_"
is a bit vague if the guest can be preempted and _now_ can be
arbitrarily deferred. The tricky part about using an absolute
time is that the guest needs to work out how to convert from a
guest time into hypervisor time...
2. Rather than kicking the timer immediately for too-short (or
negative) timeouts, it should have the option to return -ETIME, to
match the clockevents set_next_event API.
+static int lguest_clockevent_set_next_event(unsigned long delta,
+ struct clock_event_device *evt)
+{
+ ktime_t kdelta = ktime_sub(evt->next_event, ktime_get());
+ hcall(LHCALL_CLOCKEVENT, __pa(&kdelta), 0, 0);
+ return 0;
+}
Why compute kdelta? Why not just use "delta"?
J
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