Porting the block-iscsi hotplug script

[Roger Pau Monné]

El 26/2/16 a les 12:57, Gustau Pérez ha escrit:
> 
> 
> El 26/02/16 a les 11:26, Roger Pau Monné ha escrit:
>> Hello,
>>
>> I've rebased everything on top of Xen 4.5, so it can be applied to the
>> xen-tools and xen-kernel packages without issues, I've uploaded all the
>> patches to:
>>
>> https://people.freebsd.org/~royger/hotplug/
> 
>    So in my case, I'd need those patches and the patches at [1] (or the
> machine would panic at the ata stage during the boot), wouldn't I? I
> don't know if I'll be able to deal with that today or this weekend, if
> not monday I'll test and let you know.

Not any more, I've just updated the Xen ports and added the patches in [1]:

https://svnweb.freebsd.org/ports?view=revision&revision=409604

>> As you can see, each folder contains the patches that should be applied
>> to each component. With this I've been able to use the simple block
>> hotplug script that's included in the series.
>>
>> There's a limitation with block hotplug scripts, that is not specific to
>> FreeBSD (the same applies to Linux for example). You cannot use block
>> hotplug scripts with HVM guests. This is because HVM guests require a
>> QEMU instance, and in order to provide a virtual disk to QEMU it must be
>> a file or block device present on the system. Then when using block
>> hotplug scripts the block device can only be made available using what
>> we call a local attach (attaching the virtual disk to Dom0), and libxl
>> doesn't do that yet. Of course patches are very welcome to remove this
>> limitation ;). The code to perform local attaching to Dom0 is already in
>> libxl, it's just not used for this case.
>>
>> Roger.
> 
>    In fact this is the scenario I'm most interested in :) I'll first
> take a took a the current situation with PV guests and build that
> hotplug script and then I think I'd like to deal with the support for
> HVM guests.

It shouldn't be too hard, as I said the code is already there. The only
issue I foresee is that you will have to find somewhere to store the
information about the disk you have locally-attached, so you can remove
it when the guest is destroyed.

Roger.