Re: [libvirt] [PATCHv5 00/13] qemu: allow disabling certain virtio revisions

On Wed, Sep 07, 2016 at 16:13:57 +0100, Daniel Berrange wrote: > On Wed, Sep 07, 2016 at 05:10:01PM +0200, Peter Krempa wrote: > > On Wed, Aug 24, 2016 at 00:20:42 +0200, Ján Tomko wrote: > > > https://bugzilla.redhat.com/show_bug.cgi?id=1227354 [...] > > Obviously making the user responsible for correct setting is much > > easier. > > > > Sigh. It'd be great if somebody else could also state their opinion on > > this. I can't say that I'm a big fan of this approach but it looks like > > as if it would be the only sensible one. > > I tend to agree. I'd be incredibly happy if we didn't add any of this to > the XML and would simply "do the best thing" automatically. > > I'm particularly not a fan of adding something "just in case there is a > bug" Yep, that's why I don't see a reason for using --disable-modern in libvirt. It does not have any value besides working around "possible bugs". On the other hand, I'm kind of worried that with "--disable-legacy" we are entering the domain of policy decisions as it's uncertain to me whether: * Enabling it would break guests with very old drivers. * Guest firmware actually supports the modern mode (both ovmf and bios) * other possible caveats that I can't think of right now In such case we'd need to expose a knob to set it, but I'd prefer dropping the possibility to use legacy mode only since it's of no value.