Xen devel - Jan 2005 - [PATCH] Allow Xend to find device number for sdX or hdX with udev

Symptom:
When using a udev-based dom0, if you try to create a domU with a virtual
sda device and you do not have a local scsi device xm create fails.

Fix:
When using udev, only the device nodes needed are made.  The follow
patch changes Xend to return a device number based on:

http://www.lanana.org/docs/device-list/devices.txt

For sd and hd devices if stat() fails.  It was tested against both 2.0.2
and 2.0.3.

Regards,
-- 
Anthony Liguori
Linux Technology Center (LTC) - IBM Austin
E-mail: aliguori@us.ibm.com
Phone: (512) 838-1208

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

On 14 Jan 2005, at 22:00, Anthony Liguori wrote:
> Symptom:
> When using a udev-based dom0, if you try to create a domU with a 
> virtual
> sda device and you do not have a local scsi device xm create fails.
>
> Fix:
> When using udev, only the device nodes needed are made.  The follow
> patch changes Xend to return a device number based on:
>
> http://www.lanana.org/docs/device-list/devices.txt
>
> For sd and hd devices if stat() fails.  It was tested against both 
> 2.0.2
> and 2.0.3.
Another solution is to tell udev to automatically create /dev/sda1 
every time it gets started:

# mknod /etc/udev/devices b 8 1

When udev starts, all device files inside /etc/udev/devices are 
automatically copied to /dev, with no further configuration or 
triggering of hotplug or coldplug events.

NOTE: This is what I use for VMware, which needs a lot of /dev/vm* 
devices to function properly: I moved all VMware-specific device files 
into /etc/udev/devices so when udev starts, those files are copied back 
to /dev.



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Felipe Alfaro Solana wrote:
> When udev starts, all device files inside /etc/udev/devices are 
> automatically copied to /dev, with no further configuration or 
> triggering of hotplug or coldplug events.
It depends on your distribution, for example gentoo doesn''t use 
/etc/udev/devices/, but /lib/udev-state/devices.tar.bz2.

-jkt

-- 
cd /local/pub && more beer > /dev/mouth



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Anthony Liguori wrote:
> The follow patch changes Xend to return a device number based on:
>
> http://www.lanana.org/docs/device-list/devices.txt
>
> For sd and hd devices if stat() fails.
I would suggest not using stat() at all, and not using that device
list at all (even though the hd and sd parts are equal ofcourse), but
creating the mapping based on the mapping to the other direction
inside "drivers/xen/blokfront/vbd.c". That file defines the
"xvd"
devices in addition to "hd" and "sd" devices.

-- Naked




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> Anthony Liguori wrote:
> > The follow patch changes Xend to return a device number based on:
> >
> > http://www.lanana.org/docs/device-list/devices.txt
> >
> > For sd and hd devices if stat() fails.
> 
> I would suggest not using stat() at all, and not using that device
> list at all (even though the hd and sd parts are equal ofcourse), but
> creating the mapping based on the mapping to the other direction
> inside "drivers/xen/blokfront/vbd.c". That file defines the
"xvd"
> devices in addition to "hd" and "sd" devices.
We''ve considered doing the name lookup in blkfront, but there are
complications with it being done so early in the boot sequence,
and each target devices that is supported requires special case
code anyhow.

Passing linux major/minor numbers across the device channel
interface is admittedly rather ugly, but its not a big problem.

Ian


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