interrupt support with Solo5 platform

[xiaobo55x]

Hi @anttikantee @mato @ricarkol ,

Could you guys help elaborate on how does rumprun implement the interrupt support with solo5 platform?

Regards,

Haibo

[ricarkol]

Hi @xiaobo55x ,

Solo5 does not implement interrupt support. It just implements what's needed to implement an event loop: a poll call. The rumprun event loop (below netbsd) looks like this:

schedule() {
	...
	bmk_platform_splx
	for (;;) {
		curtime = bmk_platform_cpu_clock_monotonic();
		FOR thread in ALL_THREADS:
			if (thread->bt_wakeup_time <= curtime)
				bmk_sched_wake(thread);
 		bmk_platform_splhigh
		bmk_platform_cpu_block
		bmk_platform_splx
	}
	...
}

Those bmk_ functions are platform specific calls implemented for each platform
at platform/hw/, platform/xen/, and now platform/solo5/. In particular, the
functions implemented above are:

bmk_platform_splhigh		// enable interrupts
bmk_platform_splx		// disable interrupts
bmk_platform_cpu_block		// sleep until interrupt (or something happens)
bmk_platform_cpu_clock_monotonic // get monotonic time

It turns out that these functions can be trivially implemented in solo5. There are no interrupts
in solo5, so splhigh and splx are NOOPs. cpu_clock_monotonic and cpu_block map directly
to solo5 like this:

bmk_time_t
bmk_platform_cpu_clock_monotonic(void)
{
        return solo5_clock_monotonic();
}
 void bmk_platform_cpu_block(bmk_time_t until_ns)
{
        if (solo5_poll(until_ns)) // if there is pending work
                rumpcomp_ukvmif_receive();
}

Hope this helps,
Ricardo

[xiaobo55x]

Hi @ricarkol,

Thanks very much for the help! It do give us a lot inspiration to add the solo5 support to the Unikraft project.

Regards,
Haibo