qemu-devel
[Top][All Lists]
Advanced

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Qemu-devel] [RFC] Next gen kvm api


From: Avi Kivity
Subject: Re: [Qemu-devel] [RFC] Next gen kvm api
Date: Sun, 05 Feb 2012 11:44:43 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:9.0) Gecko/20111222 Thunderbird/9.0

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).

> 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).

-- 
error compiling committee.c: too many arguments to function




reply via email to

[Prev in Thread] Current Thread [Next in Thread]