Re: [patch 4/8] KVM: x86: replace hrtimer based timer emulation

From: Gleb Natapov <gleb@redhat.com>
To: Marcelo Tosatti <mtosatti@redhat.com>
Cc: kvm@vger.kernel.org
Subject: Re: [patch 4/8] KVM: x86: replace hrtimer based timer emulation
Date: Wed, 8 Jul 2009 19:40:57 +0300	[thread overview]
Message-ID: <20090708164057.GT28046@redhat.com> (raw)
In-Reply-To: <20090708163739.GA6867@amt.cnet>

On Wed, Jul 08, 2009 at 01:37:39PM -0300, Marcelo Tosatti wrote:
> On Wed, Jul 08, 2009 at 07:29:58PM +0300, Gleb Natapov wrote:
> > On Wed, Jul 08, 2009 at 10:17:21AM -0300, Marcelo Tosatti wrote:
> > > (but yes, bypassing the irq injection system its not a very beatiful
> > > shortcut, but its done in other places too eg i8254.c NMI injection via
> > > all cpus LINT0).
> > > 
> > I've looked at this. Why do you say i8254.c NMI injection bypass the irq
> > injection system? It look to me like it uses usual way to send interrupt
> > to all cpus.
> 
> It goes through apic_accept_irq so its somewhat fine. But it accesses
> the lapics of other vcpus locklessly (which does not happen via
> kvm_set_irq path due to irq_lock protection).
Ah, that the bug then. But otherwise it goes through usual interrupt
logic. Do you know why the lock is missing? Due to potential deadlock or
we just forget to lock?

--
			Gleb.