Re: [Xen-devel] [PATCH] libbxl: add support for pvscsi, iteration 1

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Olaf Hering writes ("[PATCH] libbxl: add support for pvscsi, iteration 1"):
> Add support for vscsi= in domU.cfg, add new xl commands scsi-attach,
> scsi-list, scsi-detach. The syntax follows what xend understood.
...
> +Specifies the PVSCSI devices to be provided to the guest. PVSCSI passes
> +dom0 SCSI devices as-is to the guest.
> +
> +Each B<VSCSI_SPEC_STRING> is a mapping from dom0 SCSI devices to guest 
> visible
> +SCSI devices, like 'pvdev,vdev[,option]'. Example: 
> '/dev/sdm,3:0:4:5,feature-host'

I think this docs patch dould do with some more linewrapping.

I would say "in the format" rather than "like".

> +Specifies the dom0 visible SCSI device. The string can be either a device 
> path
> +like to a block device like /dev/disk/by-id/scsi-XYZ. Or it can be a device 
> path
> +to a char device like /dev/sg5. Or it can be specified in the SCSI notation
> +HOST:CHANNEL:TARGET:LUN. Note that the latter format is unreliable because
> +the HOST value can change across dom0 reboots.

/dev/sg5 might have an unstable name too, in some cases.

You should specify what format HOST CHANNEL TARGET LUN are in.  Are
they all decimal integers ?  Can we use 0x to specify hex ?

> +=item C<vdev>
> +
> +Specifies how the SCSI device is mapped into the guest. The notation is in
> +SCSI notation HOST:CHANNEL:TARGET:LUN. HOST in this case means a virthal
> +SCSI host within the guest.

I think I don't understand "HOST".  Is it an integer ?  Does the Xen
PV SCSI interface then offer multiple virtual SCSI hosts ?  How many ?

> +=item C<option>
> +
> +Right now only one option is recognized: feature-host.

What effect does that option have ?

> diff --git a/docs/man/xl.pod.1 b/docs/man/xl.pod.1
> index 30bd4bf..5f89fca 100644
> --- a/docs/man/xl.pod.1
> +++ b/docs/man/xl.pod.1
> @@ -1219,6 +1219,26 @@ List virtual trusted platform modules for a domain.
...
> +=item B<scsi-attach> I<domain-id> I<pdev> I<vdev> I<[,feature-host]>

Does one really have to specify the comma there ?

> +=item B<scsi-detach> I<domain-id> I<vdev>
> +
> +Removes the vscsi device from domain specified by I<domain-id>.
> +Note that the whole virtual SCSI host with all its devices is removed.
> +This is a BUG!

Ouch!  Surely that needs to be fixed before we apply the patch ?

Hrm, I see I'm largely duplicating comments made by Ian Campbell.
I'll wait for a repost.

Thanks,
Ian.

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