On Fri, Jun 21, 2019 at 09:53:59 -0500, Jonathon Jongsma wrote: > On Fri, 2019-06-21 at 08:13 +0200, Peter Krempa wrote: > > On Thu, Jun 20, 2019 at 14:51:12 -0500, Jonathon Jongsma wrote: > > > Since the cirrus vga memory size isn't configurable, we can ignore > > > any > > > 'vram' attribute when parsing a domain definition. However, when no > > > value is specified, it ends up getting set to a default value of > > > 16MB. > > > This 16MB value is not used anywhere (for example, it is not passed > > > as > > > an argument to qemu), but is displayed in the XML definition. So by > > > changing this default value to 0, it will also be omitted from the > > > XML > > > definition of the domain. > > > > > > Fixes: rhbz#1447831 > > > > Please always use the full link so that it's clickable and users > > don't > > have to figure out what 'rhbz' is. > > > > > Signed-off-by: Jonathon Jongsma <jjongsma@xxxxxxxxxx> > > > --- > > > This is an attempt to apply the fix suggested by Gerd at > > > https://bugzilla.redhat.com/show_bug.cgi?id=1447831#c2. I'm not > > > totally confident that this is the right approach, since I'm > > > relatively new to the code. Another approach might be to simply > > > close > > > the bug as NOTABUG since it doesn't seem that having this unused > > > attribute in the domain definition has any significant drawbacks. > > > > We certainly should not set any default if it's not used. There's not > > much else we can do though as we did put a default into the > > configuration. > > I'm not sure I understand what you're suggesting here. This sentence > seems to imply that you think we should *not* set a default, but down > below you say that you're not certain whether we should clear the > default? It seems a bit contradictory, but perhaps I'm simply > misunderstanding. I actually meant 'clearing the memory size', thus basically just omitting the whole second hunk of your patch. So any previously set value would be kept intact. Clearing it itself is not a problem for libvirt but might be potentially unexpected by higher level management apps. But I'm not really sure whether't that's a valid case. > > > Doing any validation would mean that any VM which had the > > default errorneously configured in the XML would fail to start. > > Yeah, I did not do any 'validation' of cirrus vram attributes because I > didn't want existing VMs to fail to start. And all existing VMs that > use the cirrus device presumably have this attribute set in their XML > definition. So I simply ignored this parameter rather than rejecting > it. But as I said, I'm not sure whether that's the correct approach for > libvirt. I don't think there's much to do besides ignoring it. > > > > > Whether it's worth clearing the default or not I'm not so certain but > > I > > don't think it should hurt. > > > > You definitely should fix the docs though: > > > > https://libvirt.org/formatdomain.html#elementsVideo > > > > As it says 'For a guest of type "kvm", the default video is: type > > with > > value "cirrus", vram with value "16384" and heads with value "1".' > > > > (see docs/formatdomain.html.in ) > > Thanks, will do. > > Jonathon >
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