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Date: Thu, 19 Apr 2012 11:33:06 -0400
From: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To: Stefano Stabellini <stefano.stabellini@...citrix.com>
Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
Ian Campbell <Ian.Campbell@...rix.com>,
konrad <konrad@...alhost.localdomain>
Subject: Re: [PATCH] xen/xenbus: Add quirk to deal with misconfigured
backends.
On Thu, Apr 19, 2012 at 12:37:42PM +0100, Stefano Stabellini wrote:
> On Wed, 18 Apr 2012, Konrad Rzeszutek Wilk wrote:
> > From: konrad <konrad@...alhost.localdomain>
>
> wrong email address
Yeah :-)
>
>
> > A rather annoying and common case is when booting a PVonHVM guest
> > and exposing the PV KBD and PV VFB - as both of those do not
> > make any sense.
>
> I would rather write: "as broken toolstacks don't always initialize the
> backends correctly."
OK.
>
>
> > The HVM guest is using the VGA driver and the emulated
> > keyboard for this. So we provide a very basic quirk framework
> > (can be expanded in the future) to not wait for 6 minutes for those devices
> > to initialize - they never wont.
> >
> > To trigger this, put this in your guest config:
> >
> > vfb = [ 'vnc=1, vnclisten=0.0.0.0 ,vncunused=1']
> >
> > instead of this:
> > vnc=1
> > vnclisten="0.0.0.0"
> >
> > [v3: Split delay in non-essential (30 seconds) and essential
> > devices per Ian and Stefano suggestion]
> > Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>quirk
> > ---
> > drivers/xen/xenbus/xenbus_probe_frontend.c | 69 +++++++++++++++++++++------
> > 1 files changed, 53 insertions(+), 16 deletions(-)
> >
> > diff --git a/drivers/xen/xenbus/xenbus_probe_frontend.c b/drivers/xen/xenbus/xenbus_probe_frontend.c
> > index f20c5f1..7422913 100644
> > --- a/drivers/xen/xenbus/xenbus_probe_frontend.c
> > +++ b/drivers/xen/xenbus/xenbus_probe_frontend.c
> > @@ -135,7 +135,7 @@ static int read_backend_details(struct xenbus_device *xendev)
> > return xenbus_read_otherend_details(xendev, "backend-id", "backend");
> > }
> >
> > -static int is_device_connecting(struct device *dev, void *data)
> > +static int is_device_connecting(struct device *dev, void *data, bool ignore_vkbd)
> > {
> > struct xenbus_device *xendev = to_xenbus_device(dev);
> > struct device_driver *drv = data;
> > @@ -152,16 +152,41 @@ static int is_device_connecting(struct device *dev, void *data)
> > if (drv && (dev->driver != drv))
> > return 0;
> >
> > + if (ignore_vkbd) {
>
> I would name the parameter ignore_nonessential, just to make it clearer
> that is not just about vkbd
OK.
>
>
> > + /* With older QEMU, for PVonHVM guests the guest config files
> > + * could contain: vfb = [ 'vnc=1, vnclisten=0.0.0.0']
> > + * which is nonsensical as there is no PV FB (there can be
> > + * a PVKB) running as HVM guest. */
> > +
> > + if ((strncmp(xendev->nodename, "device/vkbd", 11) == 0))
> > + return 0;
> > +
> > + if ((strncmp(xendev->nodename, "device/vfb", 10) == 0))
> > + return 0;
> > + }
> > xendrv = to_xenbus_driver(dev->driver);
> > return (xendev->state < XenbusStateConnected ||
> > (xendev->state == XenbusStateConnected &&
> > xendrv->is_ready && !xendrv->is_ready(xendev)));
> > }
> > +static int essential_device_connecting(struct device *dev, void *data)
> > +{
> > + return is_device_connecting(dev, data, true /* ignore PVKB+PVDB */);
> > +}
>
> the comment is wrong
Oh, PVKBD + PVFB. Right.
>
>
> > +static int non_essential_device_connecting(struct device *dev, void *data)
> > +{
> > + return is_device_connecting(dev, data, false);
> > +}
> >
> > -static int exists_connecting_device(struct device_driver *drv)
> > +static int exists_essential_connecting_device(struct device_driver *drv)
> > {
> > return bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
> > - is_device_connecting);
> > + essential_device_connecting);
> > +}
> > +static int exists_non_essential_connecting_device(struct device_driver *drv)
> > +{
> > + return bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
> > + non_essential_device_connecting);
> > }
> >
> > static int print_device_status(struct device *dev, void *data)
> > @@ -192,6 +217,23 @@ static int print_device_status(struct device *dev, void *data)
> > /* We only wait for device setup after most initcalls have run. */
> > static int ready_to_wait_for_devices;
> >
> > +static bool wait_loop(unsigned long start, unsigned int max_delay,
> > + unsigned int *seconds_waited)
> > +{
> > + if (time_after(jiffies, start + (*seconds_waited+5)*HZ)) {
> > + if (!*seconds_waited)
> > + printk(KERN_WARNING "XENBUS: Waiting for "
> > + "devices to initialise: ");
> > + *seconds_waited += 5;
> > + printk("%us...", max_delay - *seconds_waited);
> > + if (*seconds_waited == max_delay)
> > + return true;
> > + }
> > +
> > + schedule_timeout_interruptible(HZ/10);
> > +
> > + return false;
> > +}
> > /*
> > * On a 5-minute timeout, wait for all devices currently configured. We need
> > * to do this to guarantee that the filesystems and / or network devices
> > @@ -215,19 +257,14 @@ static void wait_for_devices(struct xenbus_driver *xendrv)
> > if (!ready_to_wait_for_devices || !xen_domain())
> > return;
> >
> > - while (exists_connecting_device(drv)) {
> > - if (time_after(jiffies, start + (seconds_waited+5)*HZ)) {
> > - if (!seconds_waited)
> > - printk(KERN_WARNING "XENBUS: Waiting for "
> > - "devices to initialise: ");
> > - seconds_waited += 5;
> > - printk("%us...", 300 - seconds_waited);
> > - if (seconds_waited == 300)
> > - break;
> > - }
> > -
> > - schedule_timeout_interruptible(HZ/10);
> > - }
> > + while (exists_non_essential_connecting_device(drv))
> > + if (wait_loop(start, 30, &seconds_waited))
> > + break;
> > +
> > + /* Skips PVKB and PVFB check.*/
> > + while (exists_essential_connecting_device(drv))
> > + if (wait_loop(start, 270, &seconds_waited))
> > + break;
> >
> > if (seconds_waited)
> > printk("\n");
> > --
> > 1.7.7.5
> >
>
> Other than the comments I wrote above, I think the patch is good
Sweet. thx!
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