Re: [Qemu-devel] [V6 2/4] hw/core: Add AMD IOMMU to machine properties

[Marcel Apfelbaum]

On 03/02/2016 10:51 PM, David Kiarie wrote:
> On 21/02/16 23:09, Jan Kiszka wrote:
> > On 2016-02-21 19:10, David Kiarie wrote:
> > > diff --git a/qemu-options.hx b/qemu-options.hx
> > > index 2f0465e..dad160f 100644
> > > --- a/qemu-options.hx
> > > +++ b/qemu-options.hx
> > > @@ -38,7 +38,7 @@ DEF("machine", HAS_ARG, QEMU_OPTION_machine, \
> > >       "                kvm_shadow_mem=size of KVM shadow MMU\n"
> > >       "                dump-guest-core=on|off include guest memory in a core dump 
> > > (default=on)\n"
> > >       "                mem-merge=on|off controls memory merge support (default: 
> > > on)\n"
> > > -    "                iommu=on|off controls emulated Intel IOMMU (VT-d) support 
> > > (default=off)\n"
> > > +    "                iommu=amd|intel enables and selects the emulated IOMMU 
> > > (default: off)\n"
> > We should also support "iommu=off" or "none" to explicitly disable it.
> > That is consistent with other switches, and maybe there will once be a
> > machine type (chipset) with IOMMU enabled by default.
>
> We could have such but this will not be referenced anywhere in the code as the 
> IOMMU is 'off' by default. Most of the other such switches relate to properties 
> that are 'on' by default.

It doesn't matter if is not used, some management systems would prefer to pass an 
"off" value rather than not adding the property.
Also you need a default value. Even in the description you mention it as "off".

Thanks,
Marcel


> > Jan