Re: [Qemu-devel] [PATCH 1/7] qemu-doc: Document minimum kernel version for KVM in x86_64

[Eduardo Habkost <ehabkost@redhat.com>]

On Mon, Oct 09, 2017 at 03:40:02PM +0200, Paolo Bonzini wrote:
> On 06/10/2017 23:52, Eduardo Habkost wrote:
> > The default set of KVM CPU features require the host kernel to
> > support them.  KVM_PV_EOI is the newest one, and was included on
> > Linux v3.6 (Linux commit ae7a2a3f).
> > 
> > Running on an old host might break management software
> > expectations because the latest machine-type won't be runnable
> > while older machine-types might be runnable.  Document v3.6 as
> > the minimum kernel version for KVM on x86_64.
> > 
> > Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> > ---
> >  qemu-doc.texi | 9 +++++++++
> >  1 file changed, 9 insertions(+)
> > 
> > diff --git a/qemu-doc.texi b/qemu-doc.texi
> > index ecd186a159..be45b6b6f6 100644
> > --- a/qemu-doc.texi
> > +++ b/qemu-doc.texi
> > @@ -37,6 +37,7 @@
> >  * QEMU System emulator for non PC targets::
> >  * QEMU Guest Agent::
> >  * QEMU User space emulator::
> > +* System requirements::
> >  * Implementation notes::
> >  * Deprecated features::
> >  * License::
> > @@ -2348,6 +2349,14 @@ Act as if the host page size was 'pagesize' bytes
> >  Run the emulation in single step mode.
> >  @end table
> >  
> > +@node System requirements
> > +@chapter System requirements
> > +
> > +@section KVM kernel module
> > +
> > +On x86_64 hosts, the default set of CPU features enabled by the KVM accelerator
> > +require the host to be running Linux v3.6 or newer.
> > +
> >  
> >  @include qemu-tech.texi
> >  
> > 
> 
> Maybe we should expand on the consequences of running on older versions?

I intentionally tried to not make any commitment to what should
happen if running an older kernel.  But a quick explanation of
what can happen is probably a good idea.  I will try to come up
with something.

-- 
Eduardo