On Mon, Mar 02, 2015 at 10:03:35AM +0000, Stefano Stabellini wrote:
> On Fri, 27 Feb 2015, Konrad Rzeszutek Wilk wrote:
> > This has been in queue for some time.
> >
> > In our kernels (UEK3) we had to revert said patch. The patch says:
> >
> > " xen/fb: allow xenfb initialization for hvm guests
> >
> > There is no reasons why an HVM guest shouldn't be allowed to use xenfb.
> > As a matter of fact ARM guests, HVM from Linux POV, can use xenfb.
> > Given that no Xen toolstacks configure a xenfb backend for x86 HVM
> > guests, they are not affected.
> >
> > Please note that at this time QEMU needs few outstanding fixes to
> > provide xenfb on ARM:
> >
> > http://marc.info/?l=qemu-devel&m=138739419700837&w=2
> > "
> >
> > which is a lie. The "no Xen toolstacks configure a xenfb backend for
> > x86 HVM" is actually a lie. If you try to boot this kernel under
> > Xen with Xend it will be a problem - as Xend does setup an 'vfb'
> > device.
> >
> > The end result is that during the bootup - up until X starts, there is
> > no console output on the VNC window. As the Linux kernel tries to use
> > the vfb console driver.
> >
> > Any suggestsion on how to fix this? Should we just wrap the
> > whole thing with #ifdef, like this?
>
> Is vfb properly setup by Xend? Does the console show on the vfb framebuffer?
The vfb xenstore keys are. The VFB framebuffer (QEMU) is not - as it
in most cases runs as qemu-traditional which would not set it up.
>
> If the vfb console works but is undesirable because the user expects the
> output on the main vnc window (the vga framebuffer), then could we find
> a way to prioritize the vga console over vfb on x86?
This is all about Xend and QEMU traditional. Fixing the bug in Xend would
be nice but I don't see anybody accepting the patch as those are
kind of 'dead'.
>
> If the vfb console doesn't work, for example because the backend is not
> running, then maybe we could find a way in Linux to avoid vfb if it is
> not actually "connected".
That sounds complicated. Especially during early bootup.
>
>
> > diff --git a/drivers/video/fbdev/xen-fbfront.c
> > b/drivers/video/fbdev/xen-fbfront.c
> > index 09dc447..584be8e 100644
> > --- a/drivers/video/fbdev/xen-fbfront.c
> > +++ b/drivers/video/fbdev/xen-fbfront.c
> > @@ -696,7 +696,10 @@ static int __init xenfb_init(void)
> > {
> > if (!xen_domain())
> > return -ENODEV;
> > -
> > +#ifdef CONFIG_X86
> > + if (!xen_pv_domain())
> > + return -ENODEV;
> > +#endif
> > /* Nothing to do if running in dom0. */
> > if (xen_initial_domain())
> > return -ENODEV;
> >
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