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SubjectRe: [PATCH] xen/xenbus: Add quirk to deal with misconfigured backends.
On Wed, 18 Apr 2012, Konrad Rzeszutek Wilk wrote:
> From: konrad <konrad@localhost.localdomain>

wrong email address


> 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."


> 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@oracle.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


> + /* 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


> +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



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