Mailing List Archive: OpenStack: Dev

OpenStack support: KVM vs. QEMU

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lorin at nimbisservices

May 8, 2012, 1:08 PM

Post #1 of 4 (403 views)
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OpenStack support: KVM vs. QEMU

Are there any Nova features that work with KVM but don't work with QEMU? Either way, I'd like to capture this in the documentation

I know that KVM is faster than QEMU because of hardware support, but I don't know if there's additional functionality that only works with KVM. The Hypervisor support matrix wiki page <http://wiki.openstack.org/HypervisorSupportMatrix> has no specific information on OpenStack features supported by KVM but not QEMU

Take care,

Lorin
--
Lorin Hochstein
Lead Architect - Cloud Services
Nimbis Services, Inc.
www.nimbisservices.com

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razique.mahroua at gmail

May 8, 2012, 1:30 PM

Post #2 of 4 (401 views)
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Re: OpenStack support: KVM vs. QEMU [In reply to]

Hi Lorin,
not that I'm aware off. In fact, even out from Nova, both have the similar features. The only doubt I have is the implementation called "snapshot2" which is a blueprint at Qemu, but any other features are common for both. Appart the speed dev. I thnik the KVM team tries to stick to the qemu dev. when it comes to features
Razique

Nuage & Co - Razique Mahroua
razique.mahroua [at] gmail

Le 8 mai 2012 à 22:08, Lorin Hochstein a écrit :

> Are there any Nova features that work with KVM but don't work with QEMU? Either way, I'd like to capture this in the documentation
>
> I know that KVM is faster than QEMU because of hardware support, but I don't know if there's additional functionality that only works with KVM. The Hypervisor support matrix wiki page <http://wiki.openstack.org/HypervisorSupportMatrix> has no specific information on OpenStack features supported by KVM but not QEMU
>
>
> Take care,
>
> Lorin
> --
> Lorin Hochstein
> Lead Architect - Cloud Services
> Nimbis Services, Inc.
> www.nimbisservices.com
>
>
>
>
>
> _______________________________________________
> Mailing list: https://launchpad.net/~openstack
> Post to : openstack [at] lists
> Unsubscribe : https://launchpad.net/~openstack
> More help : https://help.launchpad.net/ListHelp

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jwalters at isi

May 8, 2012, 2:27 PM

Post #3 of 4 (408 views)
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Re: OpenStack support: KVM vs. QEMU [In reply to]

What about PCI passthrough? I'm not certain, because I've never tried it without KVM, but I'd be surprised if it worked outside of KVM.

JP

On May 8, 2012, at 4:30 PM, Razique Mahroua wrote:

> Hi Lorin,
> not that I'm aware off. In fact, even out from Nova, both have the similar features. The only doubt I have is the implementation called "snapshot2" which is a blueprint at Qemu, but any other features are common for both. Appart the speed dev. I thnik the KVM team tries to stick to the qemu dev. when it comes to features
> Razique
>
> Nuage & Co - Razique Mahroua
> razique.mahroua [at] gmail
>
> <NUAGECO-LOGO-Fblan_petit.jpg>
>
> Le 8 mai 2012 à 22:08, Lorin Hochstein a écrit :
>
>> Are there any Nova features that work with KVM but don't work with QEMU? Either way, I'd like to capture this in the documentation
>>
>> I know that KVM is faster than QEMU because of hardware support, but I don't know if there's additional functionality that only works with KVM. The Hypervisor support matrix wiki page <http://wiki.openstack.org/HypervisorSupportMatrix> has no specific information on OpenStack features supported by KVM but not QEMU
>>
>>
>> Take care,
>>
>> Lorin
>> --
>> Lorin Hochstein
>> Lead Architect - Cloud Services
>> Nimbis Services, Inc.
>> www.nimbisservices.com
>>
>>
>>
>>
>>
>> _______________________________________________
>> Mailing list: https://launchpad.net/~openstack
>> Post to : openstack [at] lists
>> Unsubscribe : https://launchpad.net/~openstack
>> More help : https://help.launchpad.net/ListHelp
>
> _______________________________________________
> Mailing list: https://launchpad.net/~openstack
> Post to : openstack [at] lists
> Unsubscribe : https://launchpad.net/~openstack
> More help : https://help.launchpad.net/ListHelp

Christoph.Hellwig at nebula

May 11, 2012, 12:01 AM

Post #4 of 4 (404 views)
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Re: OpenStack support: KVM vs. QEMU [In reply to]

On Tue, 2012-05-08 at 16:08 -0400, Lorin Hochstein wrote:
> Are there any Nova features that work with KVM but don't work with
> QEMU? Either way, I'd like to capture this in the documentation
>
> I know that KVM is faster than QEMU because of hardware support, but I
> don't know if there's additional functionality that only works with
> KVM. The Hypervisor support matrix wiki page
> <http://wiki.openstack.org/HypervisorSupportMatrix> has no specific
> information on OpenStack features supported by KVM but not QEMU

The first question is what do you mean with KVM? Any qemu binary using
kernel acceleration by using the kvm kernel module, or using the
qemu-kvm fork that's slowly getting merged back into qemu mainline (it's
down to about 5000 LOC difference now) in either kvm or tcq mode?

There should be no feature difference between using hardware accelerated
KVM mode, and TCG emulation, unless you call boots a reasonable cloud in
your lifetime a feature, or if you look the other way around running
foreign architecture OS images, which is something KVM can't do.

There are features not merged back into mainline qemu, with device
assignment being the last one in current mainline, and MSI(X) and the
I/O thread support others in common released versions. In theory these
also should work using TCG in qemu-kvm, although it's very unlikely to
be tested very well.

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