From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Vrabel Subject: Re: Debian Kernel: Xen-fb-frontend as a module? Date: Wed, 24 Sep 2014 11:28:27 +0100 Message-ID: <54229CCB.5000903@citrix.com> References: <54217076.9030508@rcpt.to> <1411482601.1781.56.camel@kazak.uk.xensource.com> <54219539.3090108@citrix.com> <1411487846.1781.83.camel@kazak.uk.xensource.com> <20140923191458.GZ3007@laptop.dumpdata.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Stefano Stabellini , Konrad Rzeszutek Wilk Cc: James Bromberger , Stefano Stabellini , debian-kernel@lists.debian.org, xen-devel , Ian Campbell List-Id: xen-devel@lists.xenproject.org On 24/09/14 11:23, Stefano Stabellini wrote: > On Tue, 23 Sep 2014, Konrad Rzeszutek Wilk wrote: >> On Tue, Sep 23, 2014 at 04:57:26PM +0100, Ian Campbell wrote: >>> On Tue, 2014-09-23 at 16:43 +0100, David Vrabel wrote: >>>> On 23/09/14 15:30, Ian Campbell wrote: >>>>> create ! >>>>> title it "30s delay loading xenfb driver on some systems" >>>>> owner it Konrad Rzeszutek Wilk >>>>> thanks >>>>> >>>>> Hi James, >>>>> >>>>> Some of the other Xen devs were discussing an issue which sounded >>>>> awfully similar to this one, so I am copying the xen-devel list and >>>>> creating a Xen bug to track the issue, please CC xen-devel (no need to >>>>> subscribe but you may be moderated the first time), since the tracker >>>>> slurps mails from the list. >>>>> >>>>> I'm not sure of the details of the other issue but it involved >>>>> http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=b1a3b1c8a8d963424c4699efa64dd8986b2f76d7 hopefully Konrad or one of the others will follow up. >> >> That was with an HVM guest running under Xen 4.1 in which this >> guest config was used: >> >> vfb = ['type=vnc,vncunused=1,vnclisten=0.0.0.0'] >> >> Xend would create an XenStore keys for the PV framebuffer and also making >> sure that QEMU VGA driver was running. The end result was that the guest >> would boot up to Xorg VGA driver, but the frame buffer console (so from >> the moment GRUB2 started Linux up to Xorg) would try to use the xen-fbfront. >> >> And since this is HVM guest and VNCviewer was slurping contents from the >> VGA buffer - which was not used at all - we wouldn't get anything. >> >> Reverting the above patch fixed the issue. > > If you have a vfb line in your config file, aren't you actually > explicitly requesting a vfb frontend/backend pair? > XenD is just doing what the user asked him to do, I wouldn't call this a > bug. > > What is strange is that given that there is no running vfb backend for > HVM guests in a regular Xen 4.1 installation, xen-fbfront could never > reach the "connected" state ("4" on xenstore): so why is Linux trying to > use vfb when the frontend is not even connected? > > The reason is that xenfb_probe calls register_framebuffer and > xenfb_make_preferred_console too early, before even knowing if the > backend is alive. > > I would move the register_framebuffer and xenfb_make_preferred_console > calls in xenfb_backend_changed, case XenbusStateConnected. That should > fix it. I don't think that will help. Registering the frontend driver will still wait for CONNECTED, regardless of whether the frame buffer will actually be used. David