On Tue, 10 Oct 2017 22:11:46 +1100 Michael Ellerman <m...@ellerman.id.au> wrote:
> Nicholas Piggin <npig...@gmail.com> writes: > > > OPAL boot does not insert secondaries at 0x60 to wait at the secondary > > hold spinloop. Instead it keeps them held in firmware until the > > opal_start_cpu call is made, which directs them where the caller > > specifies. Linux inserts them into generic_secondary_smp_init(), which > > is after the secondary hold spinloop (they go on to spin at the per-CPU > > paca loops, but that is another step). > > > > So avoid waiting on this spinloop when booting with OPAL firmware. > > It always just times out. > > > > This saves 100ms boot time on bare metal, and 10s of seconds when > > booting the simulator in SMP. > > Oh nice, that's real facepalm territory. > > It'd be neater if we just inserted them at 0x60, but the sequence is > wrong. > > Can we fix it just by making spinning_secondaries zero on OPAL? I had a look at that, but generic_secondary_smp_init() still decrements it, so it would underflow which I thought was uglier. I actually have to look a bit further, because KVM guests are also having the loop time out too by the looks. Thanks, Nick
