Re: frequent lockups in 3.18rc4

From: Andy Lutomirski
Date: Fri Nov 21 2014 - 15:02:47 EST

On Fri, Nov 21, 2014 at 12:00 PM, Dave Jones <davej@xxxxxxxxxx> wrote:
> On Fri, Nov 21, 2014 at 11:46:57AM -0800, Linus Torvalds wrote:
> > Anybody who seriously does virtualization uses hw virtualization that
> > is much better than it used to be. And the non-serious users aren't
> > that performance-sensitive by definition.
> >
> > I note that the Fedora kernel config seems to include paravirt by
> > default, so you get a lot of the crazy overheads..
> I'm not sure how many people actually use paravirt these days,
> but the reason Fedora has it enabled still at least is probably
> because..
> config KVM_GUEST
> bool "KVM Guest support (including kvmclock)"
> depends on PARAVIRT
> But tbh I've not looked at this stuff since it first got merged.
> Will a full-virt system kvm boot a guest without KVM_GUEST enabled ?
> (ie, is this just an optimisation for the paravirt case?)

It will boot just fine, although there may be some timing glitches.

I think we should have PARAVIRT_LITE that's just enough for KVM. That
probably involves some apic changes and nothing else.


> I'm not a heavy virt user, so I don't even remember how a lot of
> this stuff is supposed to work.
> Dave

Andy Lutomirski
AMA Capital Management, LLC
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