From: Avi Kivity <avi@redhat.com>
To: Gleb Natapov <gleb@redhat.com>
Cc: KVM list <kvm@vger.kernel.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
qemu-devel <qemu-devel@nongnu.org>
Subject: Re: [RFC] Next gen kvm api
Date: Sun, 05 Feb 2012 11:56:21 +0200 [thread overview]
Message-ID: <4F2E5245.3070400@redhat.com> (raw)
In-Reply-To: <20120205095153.GA29265@redhat.com>
On 02/05/2012 11:51 AM, Gleb Natapov wrote:
> On Sun, Feb 05, 2012 at 11:44:43AM +0200, Avi Kivity wrote:
> > On 02/05/2012 11:37 AM, Gleb Natapov wrote:
> > > On Thu, Feb 02, 2012 at 06:09:54PM +0200, Avi Kivity wrote:
> > > > Device model
> > > > ------------
> > > > Currently kvm virtualizes or emulates a set of x86 cores, with or
> > > > without local APICs, a 24-input IOAPIC, a PIC, a PIT, and a number of
> > > > PCI devices assigned from the host. The API allows emulating the local
> > > > APICs in userspace.
> > > >
> > > > The new API will do away with the IOAPIC/PIC/PIT emulation and defer
> > > > them to userspace. Note: this may cause a regression for older guests
> > > > that don't support MSI or kvmclock. Device assignment will be done
> > > > using VFIO, that is, without direct kvm involvement.
> > > >
> > > So are we officially saying that KVM is only for modern guest
> > > virtualization?
> >
> > No, but older guests may have reduced performance in some workloads
> > (e.g. RHEL4 gettimeofday() intensive workloads).
> >
> Reduced performance is what I mean. Obviously old guests will continue working.
I'm not happy about it either.
> > > Also my not so old host kernel uses MSI only for NIC.
> > > SATA and USB are using IOAPIC (though this is probably more HW related
> > > than kernel version related).
> >
> > For devices emulated in userspace, it doesn't matter where the IOAPIC
> > is. It only matters for kernel provided devices (PIT, assigned devices,
> > vhost-net).
> >
> What about EOI that will have to do additional exit to userspace for each
> interrupt delivered?
I think the ioapic EOI is asynchronous wrt the core, yes? So the vcpu
can just post the EOI broadcast on the apic-bus socketpair, waking up
the thread handling the ioapic, and continue running. This trades off
vcpu latency for using more host resources.
--
error compiling committee.c: too many arguments to function
next prev parent reply other threads:[~2012-02-05 9:56 UTC|newest]
Thread overview: 89+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-02-02 16:09 [RFC] Next gen kvm api Avi Kivity
[not found] ` <CAB9FdM9M2DWXBxxyG-ez_5igT61x5b7ptw+fKfgaqMBU_JS5aA@mail.gmail.com>
2012-02-02 22:16 ` [Qemu-devel] " Rob Earhart
2012-02-05 13:14 ` Avi Kivity
2012-02-06 17:41 ` Rob Earhart
2012-02-06 19:11 ` Anthony Liguori
2012-02-07 12:03 ` Avi Kivity
2012-02-07 15:17 ` Anthony Liguori
2012-02-07 16:02 ` Avi Kivity
2012-02-07 16:18 ` Jan Kiszka
2012-02-07 16:21 ` Anthony Liguori
2012-02-07 16:29 ` Jan Kiszka
2012-02-15 13:41 ` Avi Kivity
2012-02-07 16:19 ` Anthony Liguori
2012-02-15 13:47 ` Avi Kivity
2012-02-07 12:01 ` Avi Kivity
2012-02-03 2:09 ` Anthony Liguori
2012-02-04 2:08 ` Takuya Yoshikawa
2012-02-22 13:06 ` Peter Zijlstra
2012-02-05 9:24 ` Avi Kivity
2012-02-07 1:08 ` Alexander Graf
2012-02-07 12:24 ` Avi Kivity
2012-02-07 12:51 ` Alexander Graf
2012-02-07 13:16 ` Avi Kivity
2012-02-07 13:40 ` Alexander Graf
2012-02-07 14:21 ` Avi Kivity
2012-02-07 14:39 ` Alexander Graf
2012-02-15 11:18 ` Avi Kivity
2012-02-15 11:57 ` Alexander Graf
2012-02-15 13:29 ` Avi Kivity
2012-02-15 13:37 ` Alexander Graf
2012-02-15 13:57 ` Avi Kivity
2012-02-15 14:08 ` Alexander Graf
2012-02-16 19:24 ` Avi Kivity
2012-02-16 19:34 ` Alexander Graf
2012-02-16 19:38 ` Avi Kivity
2012-02-16 20:41 ` Scott Wood
2012-02-17 0:23 ` Alexander Graf
2012-02-17 18:27 ` Scott Wood
2012-02-18 9:49 ` Avi Kivity
2012-02-17 0:19 ` Alexander Graf
2012-02-18 10:00 ` Avi Kivity
2012-02-18 10:43 ` Alexander Graf
2012-02-15 19:17 ` Scott Wood
2012-02-12 7:10 ` Takuya Yoshikawa
2012-02-15 13:32 ` Avi Kivity
2012-02-07 15:23 ` Anthony Liguori
2012-02-07 15:28 ` Alexander Graf
2012-02-08 17:20 ` Alan Cox
2012-02-15 13:33 ` Avi Kivity
2012-02-15 22:14 ` Arnd Bergmann
2012-02-10 3:07 ` Jamie Lokier
2012-02-03 18:07 ` Eric Northup
2012-02-03 22:52 ` [Qemu-devel] " Anthony Liguori
2012-02-06 19:46 ` Scott Wood
2012-02-07 6:58 ` Michael Ellerman
2012-02-07 10:04 ` Alexander Graf
2012-02-15 22:21 ` Arnd Bergmann
2012-02-16 1:04 ` Michael Ellerman
2012-02-16 19:28 ` Avi Kivity
2012-02-17 0:09 ` Michael Ellerman
2012-02-18 10:03 ` Avi Kivity
2012-02-16 10:26 ` Avi Kivity
2012-02-07 12:28 ` Anthony Liguori
2012-02-07 12:40 ` Avi Kivity
2012-02-07 12:51 ` Anthony Liguori
2012-02-07 13:18 ` Avi Kivity
2012-02-07 15:15 ` Anthony Liguori
2012-02-07 18:28 ` Chris Wright
2012-02-08 17:02 ` Scott Wood
2012-02-08 17:12 ` Alan Cox
2012-02-05 9:37 ` Gleb Natapov
2012-02-05 9:44 ` Avi Kivity
2012-02-05 9:51 ` Gleb Natapov
2012-02-05 9:56 ` Avi Kivity [this message]
2012-02-05 10:58 ` Gleb Natapov
2012-02-05 13:16 ` Avi Kivity
2012-02-05 16:36 ` [Qemu-devel] " Anthony Liguori
2012-02-06 9:34 ` Avi Kivity
2012-02-06 13:33 ` Anthony Liguori
2012-02-06 13:54 ` Avi Kivity
2012-02-06 14:00 ` Anthony Liguori
2012-02-06 14:08 ` Avi Kivity
2012-02-07 18:12 ` Rusty Russell
2012-02-15 13:39 ` Avi Kivity
2012-02-15 21:59 ` Anthony Liguori
2012-02-16 8:57 ` Gleb Natapov
2012-02-16 14:46 ` Anthony Liguori
2012-02-16 19:34 ` Avi Kivity
2012-02-15 23:08 ` Rusty Russell
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