From: "Daniel P. Berrangé" <berrange@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: ehabkost@redhat.com, kvm@vger.kernel.org, mtosatti@redhat.com,
qemu-devel@nongnu.org, dgilbert@redhat.com,
Liran Alon <liran.alon@oracle.com>,
rth@twiddle.net, jmattson@google.com
Subject: Re: [QEMU PATCH v2 0/2]: KVM: i386: Add support for save and restore nested state
Date: Mon, 12 Nov 2018 16:18:29 +0000 [thread overview]
Message-ID: <20181112161829.GU3602@redhat.com> (raw)
In-Reply-To: <f58da4e8-aa40-2659-8db6-42c2b47f5b2f@redhat.com>
On Sun, Nov 04, 2018 at 11:19:57PM +0100, Paolo Bonzini wrote:
> On 02/11/2018 17:54, Daniel P. Berrangé wrote:
> > We have usually followed a rule that new machine types must not
> > affect runability of a VM on a host. IOW new machine types should
> > not introduce dependancies on specific kernels, or hardware features
> > such as CPU flags.
>
> > Anything that requires a new kernel feature thus ought to be an
> > opt-in config tunable on the CLI, separate from machine type
> > choice.
>
> Unless someone tinkered with the module parameters, they could not even
> use nested virtualization before 4.20. So for everyone else, "-cpu
> ...,+vmx" does count as an "opt-in config tunable on the CLI" that
> requires 4.20.
>
> For those that did tinker with module parameters, we can grandfather in
> the old machine types, so that they can use nested virtualization with
> no live migration support. For those that did not, however, I don't
> think it makes sense to say "oh by the way I really want to be able to
> migrate this VM" on the command line, or even worse on the monitor.
IIUC, 4.20 is only required from POV of migration state. Is it thus
possible to just register a migration blocker if QEMU is launched
on a host with kernel < 4.20.
Migration has always been busted historically, so those people using
nested VMX already won't be hurt by not having ability to live migrate
their VM, but could otherwise continue using them without being forced
to upgrade their kernel to fix a feature they're not even using.
Regards,
Daniel
--
|: https://berrange.com -o- https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org -o- https://fstop138.berrange.com :|
|: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
WARNING: multiple messages have this Message-ID (diff)
From: "Daniel P. Berrangé" <berrange@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Liran Alon <liran.alon@oracle.com>,
jmattson@google.com, ehabkost@redhat.com, kvm@vger.kernel.org,
mtosatti@redhat.com, qemu-devel@nongnu.org, dgilbert@redhat.com,
rth@twiddle.net
Subject: Re: [Qemu-devel] [QEMU PATCH v2 0/2]: KVM: i386: Add support for save and restore nested state
Date: Mon, 12 Nov 2018 16:18:29 +0000 [thread overview]
Message-ID: <20181112161829.GU3602@redhat.com> (raw)
In-Reply-To: <f58da4e8-aa40-2659-8db6-42c2b47f5b2f@redhat.com>
On Sun, Nov 04, 2018 at 11:19:57PM +0100, Paolo Bonzini wrote:
> On 02/11/2018 17:54, Daniel P. Berrangé wrote:
> > We have usually followed a rule that new machine types must not
> > affect runability of a VM on a host. IOW new machine types should
> > not introduce dependancies on specific kernels, or hardware features
> > such as CPU flags.
>
> > Anything that requires a new kernel feature thus ought to be an
> > opt-in config tunable on the CLI, separate from machine type
> > choice.
>
> Unless someone tinkered with the module parameters, they could not even
> use nested virtualization before 4.20. So for everyone else, "-cpu
> ...,+vmx" does count as an "opt-in config tunable on the CLI" that
> requires 4.20.
>
> For those that did tinker with module parameters, we can grandfather in
> the old machine types, so that they can use nested virtualization with
> no live migration support. For those that did not, however, I don't
> think it makes sense to say "oh by the way I really want to be able to
> migrate this VM" on the command line, or even worse on the monitor.
IIUC, 4.20 is only required from POV of migration state. Is it thus
possible to just register a migration blocker if QEMU is launched
on a host with kernel < 4.20.
Migration has always been busted historically, so those people using
nested VMX already won't be hurt by not having ability to live migrate
their VM, but could otherwise continue using them without being forced
to upgrade their kernel to fix a feature they're not even using.
Regards,
Daniel
--
|: https://berrange.com -o- https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org -o- https://fstop138.berrange.com :|
|: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
next prev parent reply other threads:[~2018-11-12 16:18 UTC|newest]
Thread overview: 96+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-16 12:46 [QEMU PATCH v2 0/2]: KVM: i386: Add support for save and restore nested state Liran Alon
2018-09-16 12:46 ` [Qemu-devel] " Liran Alon
2018-09-16 12:46 ` [QEMU PATCH v2 1/2] i386: Compile CPUX86State xsave_buf only when support KVM or HVF Liran Alon
2018-09-16 12:46 ` [Qemu-devel] " Liran Alon
2018-09-16 12:46 ` [QEMU PATCH v2 2/2] KVM: i386: Add support for save and restore nested state Liran Alon
2018-09-16 12:46 ` [Qemu-devel] " Liran Alon
2018-10-08 17:21 ` [QEMU PATCH v2 0/2]: " Liran Alon
2018-10-08 17:21 ` [Qemu-devel] " Liran Alon
2018-10-15 18:10 ` Liran Alon
2018-10-15 18:10 ` [Qemu-devel] " Liran Alon
2018-10-31 1:03 ` Liran Alon
2018-10-31 1:03 ` [Qemu-devel] " Liran Alon
2018-10-31 18:17 ` Eduardo Habkost
2018-10-31 18:17 ` [Qemu-devel] " Eduardo Habkost
2018-10-31 18:19 ` Paolo Bonzini
2018-10-31 18:19 ` [Qemu-devel] " Paolo Bonzini
2018-10-31 18:50 ` Liran Alon
2018-10-31 18:50 ` [Qemu-devel] " Liran Alon
2018-10-31 18:59 ` Dr. David Alan Gilbert
2018-10-31 18:59 ` [Qemu-devel] " Dr. David Alan Gilbert
2018-10-31 23:17 ` Liran Alon
2018-10-31 23:17 ` [Qemu-devel] " Liran Alon
2018-11-01 13:10 ` Dr. David Alan Gilbert
2018-11-01 13:10 ` [Qemu-devel] " Dr. David Alan Gilbert
2018-11-01 15:23 ` Liran Alon
2018-11-01 15:23 ` [Qemu-devel] " Liran Alon
2018-11-01 15:56 ` Dr. David Alan Gilbert
2018-11-01 15:56 ` [Qemu-devel] " Dr. David Alan Gilbert
2018-11-01 16:45 ` Jim Mattson via Qemu-devel
2018-11-01 16:45 ` [Qemu-devel] " Jim Mattson
2018-11-02 3:46 ` Liran Alon
2018-11-02 3:46 ` [Qemu-devel] " Liran Alon
2018-11-02 9:40 ` Paolo Bonzini
2018-11-02 9:40 ` [Qemu-devel] " Paolo Bonzini
2018-11-02 12:35 ` Dr. David Alan Gilbert
2018-11-02 12:35 ` [Qemu-devel] " Dr. David Alan Gilbert
2018-11-02 12:40 ` Daniel P. Berrangé
2018-11-02 12:40 ` [Qemu-devel] " Daniel P. Berrangé
2018-11-04 22:12 ` Paolo Bonzini
2018-11-04 22:12 ` [Qemu-devel] " Paolo Bonzini
2018-11-02 12:59 ` Liran Alon
2018-11-02 12:59 ` [Qemu-devel] " Liran Alon
2018-11-02 16:44 ` Jim Mattson via Qemu-devel
2018-11-02 16:44 ` [Qemu-devel] " Jim Mattson
2018-11-02 16:58 ` Daniel P. Berrangé
2018-11-02 16:58 ` [Qemu-devel] " Daniel P. Berrangé
2018-11-02 17:01 ` Jim Mattson via Qemu-devel
2018-11-02 17:01 ` [Qemu-devel] " Jim Mattson
2018-11-02 16:54 ` Daniel P. Berrangé
2018-11-02 16:54 ` [Qemu-devel] " Daniel P. Berrangé
2018-11-02 16:58 ` Dr. David Alan Gilbert
2018-11-02 16:58 ` [Qemu-devel] " Dr. David Alan Gilbert
2018-11-04 22:19 ` Paolo Bonzini
2018-11-04 22:19 ` [Qemu-devel] " Paolo Bonzini
2018-11-12 16:18 ` Daniel P. Berrangé [this message]
2018-11-12 16:18 ` Daniel P. Berrangé
2018-11-12 16:50 ` Dr. David Alan Gilbert
2018-11-12 16:50 ` [Qemu-devel] " Dr. David Alan Gilbert
2018-11-12 16:53 ` Paolo Bonzini
2018-11-12 16:53 ` [Qemu-devel] " Paolo Bonzini
2018-11-12 16:54 ` Daniel P. Berrangé
2018-11-12 16:54 ` [Qemu-devel] " Daniel P. Berrangé
2018-11-13 0:00 ` Liran Alon
2018-11-13 0:00 ` [Qemu-devel] " Liran Alon
2018-11-13 0:07 ` Jim Mattson via Qemu-devel
2018-11-13 0:07 ` [Qemu-devel] " Jim Mattson
2018-11-13 0:09 ` Liran Alon
2018-11-13 0:09 ` [Qemu-devel] " Liran Alon
2018-11-12 23:58 ` Liran Alon
2018-11-12 23:58 ` [Qemu-devel] " Liran Alon
2018-11-02 16:39 ` Jim Mattson via Qemu-devel
2018-11-02 16:39 ` [Qemu-devel] " Jim Mattson
2018-11-03 2:02 ` Liran Alon
2018-11-03 2:02 ` [Qemu-devel] " Liran Alon
2018-11-08 0:13 ` Liran Alon
2018-11-08 0:13 ` [Qemu-devel] " Liran Alon
2018-11-08 0:45 ` Jim Mattson via Qemu-devel
2018-11-08 0:45 ` [Qemu-devel] " Jim Mattson
2018-11-08 9:50 ` Paolo Bonzini
2018-11-08 9:50 ` [Qemu-devel] " Paolo Bonzini
2018-11-08 9:57 ` Liran Alon
2018-11-08 9:57 ` [Qemu-devel] " Liran Alon
2018-11-08 17:02 ` Paolo Bonzini
2018-11-08 17:02 ` [Qemu-devel] " Paolo Bonzini
2018-11-08 18:41 ` Liran Alon
2018-11-08 18:41 ` [Qemu-devel] " Liran Alon
2018-11-08 20:34 ` Paolo Bonzini
2018-11-08 20:34 ` [Qemu-devel] " Paolo Bonzini
2018-11-12 14:51 ` Dr. David Alan Gilbert
2018-11-12 14:51 ` [Qemu-devel] " Dr. David Alan Gilbert
2018-11-01 19:03 ` Liran Alon
2018-11-01 19:03 ` [Qemu-devel] " Liran Alon
2018-11-01 19:07 ` Dr. David Alan Gilbert
2018-11-01 19:07 ` [Qemu-devel] " Dr. David Alan Gilbert
2018-11-01 19:41 ` Jim Mattson via Qemu-devel
2018-11-01 19:41 ` [Qemu-devel] " Jim Mattson
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