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Re: [Qemu-devel] [RFC] Next gen kvm api
From: |
Gleb Natapov |
Subject: |
Re: [Qemu-devel] [RFC] Next gen kvm api |
Date: |
Sun, 5 Feb 2012 11:51:53 +0200 |
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.
> > 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?
--
Gleb.
- Re: [Qemu-devel] [RFC] Next gen kvm api, (continued)
- Re: [Qemu-devel] [RFC] Next gen kvm api, Avi Kivity, 2012/02/07
- Re: [Qemu-devel] [RFC] Next gen kvm api, Jan Kiszka, 2012/02/07
- Re: [Qemu-devel] [RFC] Next gen kvm api, Anthony Liguori, 2012/02/07
- Re: [Qemu-devel] [RFC] Next gen kvm api, Jan Kiszka, 2012/02/07
- Re: [Qemu-devel] [RFC] Next gen kvm api, Avi Kivity, 2012/02/15
- Re: [Qemu-devel] [RFC] Next gen kvm api, Anthony Liguori, 2012/02/07
- Re: [Qemu-devel] [RFC] Next gen kvm api, Avi Kivity, 2012/02/15
- Re: [Qemu-devel] [RFC] Next gen kvm api, Avi Kivity, 2012/02/07
Re: [Qemu-devel] [RFC] Next gen kvm api, Gleb Natapov, 2012/02/05
Re: [Qemu-devel] [RFC] Next gen kvm api, Anthony Liguori, 2012/02/05
Re: [Qemu-devel] [RFC] Next gen kvm api, Avi Kivity, 2012/02/06
Re: [Qemu-devel] [RFC] Next gen kvm api, Anthony Liguori, 2012/02/06
Re: [Qemu-devel] [RFC] Next gen kvm api, Avi Kivity, 2012/02/06
Re: [Qemu-devel] [RFC] Next gen kvm api, Anthony Liguori, 2012/02/06
Re: [Qemu-devel] [RFC] Next gen kvm api, Avi Kivity, 2012/02/06
Re: [Qemu-devel] [RFC] Next gen kvm api, Rusty Russell, 2012/02/07