Re: frequent lockups in 3.18rc4

From: Dave Jones
Date: Fri Nov 21 2014 - 15:02:39 EST


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?)

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

Dave

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