Cannot turn iommu on inside guest

[Mauricio Tavares]

On Tue, Feb 11, 2020 at 9:17 AM Daniel P. Berrangé <berrange at redhat.com> wrote:
>
> On Tue, Feb 11, 2020 at 09:09:36AM -0500, Mauricio Tavares wrote:
> > So I want to turn iommu support on in a guest (    <type arch='x86_64'
> > machine='pc-q35-4.1'>hvm</type>). Per [1] I tried to add to devices
> > either
> >
> > <devices>
> >   <iommu model='intel'>
> >     <driver intremap='on'/>
> >   </iommu>
> > </devices>
> >
> > or just a simpler
> >
> > <devices>
> >   <iommu model='intel /'>
> > </devices>
> >
> > However, when I try to boot it, it crashes with the following error
> > message (stolen from /var/log/libvirt/qemu/testkvm.log):
> >
> > 2020-02-11T05:13:27.278707Z qemu-system-x86_64: We need to set
> > caching-mode=on for intel-iommu to enable device assignment with IOMMU
> > protection.
> > 2020-02-11 05:13:27.577+0000: shutting down, reason=crashed
> >
> > that sounds like it wants me to do something like
> >
> > qemu-system-x86_64 [...] -device intel-iommu,intremap=on,caching-mode=on[2]
> >
> > using virsh. But
> >
> > <devices>
> >   <iommu model='intel'>
> >     <driver intremap='on' caching-mode='on '/>
>
> You need   caching_mode="on"  - notice underscore, not hypehn

      Much happier.  Thanks!

>
> >   </iommu>
> > </devices>
> >
> > is not only not mentioned in [1] but also fails
>
> The correctly spelt caching_mode is mentioned there.
>
> >
> > [root at testbox tests]# virsh edit testkvm
> > error: XML document failed to validate against schema: Unable to
> > validate doc against /usr/share/libvirt/schemas/domain.rng
> > Extra element devices in interleave
> > Element domain failed to validate content
> >
> > Failed. Try again? [y,n,i,f,?]:
> >
> > Can anyone show me what I am missing here?
> >
> > [1] https://libvirt.org/formatdomain.html#elementsIommu
> > [2] https://wiki.qemu.org/Features/VT-d#Command_Line_Example_2
> >
> >
>
> Regards,
> Daniel
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