Date: Mon, 31 Aug 2020 09:55:03 +0200 From: Roger Pau =?utf-8?B?TW9ubsOp?= <roger.pau@citrix.com> To: Brian Buhrow <buhrow@nfbcal.org> Cc: <freebsd-xen@freebsd.org> Subject: Re: The vnclisten parameter is ignored with hvm domains under xen-4.12.1 and FreeBSD-12.0 Message-ID: <20200831075009.GE734@Air-de-Roger> In-Reply-To: <202008282111.07SLB7TW001877@nfbcal.org> References: <20200828165658.GD734@Air-de-Roger> <202008282111.07SLB7TW001877@nfbcal.org>
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On Fri, Aug 28, 2020 at 02:11:07PM -0700, Brian Buhrow wrote: > hello Roger. thanks for the quick reply. I think, after a careful > read of the xl.cfg man page plus a careful reading of the xen-tools source > code, I've figured out the issue. I'm sending the solution here so folks > will have it in the future. > > If one is configuring an hvm guest, any vfb specifications in the domain > configuration are ignored. Let me clarify this a bit. vfb is a para-virtualized frame buffer, so it needs a specific Xen vfb driver in the guest for it to be able to use the device (ie: it's not an emulated graphics card). > Instead, the parameters that normally get placed > in a vfb stanza must be placed as top level configuration items. For > example: > > For a PV guest: > vfb = [ 'vnc=1,vnclisten=10.14.200.200' ] > > Translates to, for an hvm guest: > > vnc = 1 > vnclisten = "10.14.200.200" OTOH, the global vnc parameter is indeed exclusive to HVM guests and is related to the emulated graphics card device. You could have a HVM guest making use of both the emulated graphics card (the global vnc parameter) and nmultiple para-virtualized vfb framebuffers, but those would be different outputs (like having more than one graphics card on a physical box). You cannot however make use of the global vnc parameter for PV guests, as they have no emulated graphics card. > > The xl.cfg man page doesn't say that in order for the vnc parameters to be > picked up for hvm guests with emulated graphics cards, those parameters > need to be specified as top level parameters in the config file. It took > reading the source code of the xen-tools xl code to figure that out. Sorry, I understand this is quite confusing. Do you think the man page could be modified to make this easier to understand and create less confusion? I'm quite sure the community would be happy to take a patch in order to clarify stuff. Thanks, Roger.
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