Re: [Xen-devel] [PATCH RFC] libxl: make firmware_override able to cope with relative path

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 08/08/16 17:09, Ian Jackson wrote:
> Andrew Cooper writes ("Re: [PATCH RFC] libxl: make firmware_override able to 
> cope with relative path"):
>> The important bit which XTF and regular users want is relative to the
>> .cfg file, rather than $CWD.
> Consider:
>
>   cd /root/foo
>   xl create dir/vm1/vm1.cfg
>
>   cd /root/bar
>   xl block-attach vm1 vdev=xvdc target=file.img
>
> Where do you think `file.img' should be searched for:
>
>   - /root/foo/dir/vm1/vm1.cfg
>   - /root/bar/dir/vm1/vm1.cfg
>   - /root/bar/file.img
>
> ?  (4 marks)

In this case, /root/bar/file.img and nowhere else.

Once `xl create` is complete, the location of vm1.cfg on disk, or the
$CWD used to build it are not relevant.  The subsequent block-attach is
therefore unrelated.

>
> In your answer, consider how your proposal would be implemented, given
> that there may be xl, a qemu device model, and blkback, to consider.
> Sketch how any necessary additional state would be stored in libxl.
> (4 marks)

N/A

>
> Discuss what should happen when the domain is subsequently migrated.
> (4 marks)

No change.

In both of these cases, they are boot-time artefacts with no further
action on migrate; they live in the memory stream at that point.

~Andrew

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