Re: [PATCH] hw/s390x: Restrict "loadparm" property to devices that can be used for booting

[Thomas Huth]

On 13/11/2024 15.49, Jared Rossi wrote:
...
> Hi Thomas,
>
> Thanks for putting this fix together.  As we previously discussed, I do agree
> that my naive implementation of the “loadparm” property at the top-level
> CcwDevice was not satisfactory, and certainly virtio-gpu and virtio-tablet
> should not have a “loadparm.”
>
> The reason I had not yet submitted a fix is that I’ve gotten some feedback from
> the Libvirt side that suggests the CcwDevice implementation is not sufficient
> in general.  Libvirt will require that non-ccw devices (e.g. scsi-hd) also
> support per-device loadparm.  I do not yet know how to add that type of support
> and given that we are in hard freeze I’m not sure it is possible now.
>
> Obviously this is not ideal, and I truly do apologize for the confusion.

 Hi Jared,

yes, that scsi-hd problem is a little bit tricky, since it's common code 
that we should not "pollute" too much with s390x specific stuff, especially 
since we're in hard freeze now.

After staring at the code for quite a while, I think one option might be to 
just add a string "loadparm" property to the SCSI devices, that's just a 
simple two-line change to the common code. Patch suggestion can be found here:

 20241114122919.973930-1-thuth@redhat.com/">https://lore.kernel.org/qemu-devel/20241114122919.973930-1-thuth@redhat.com/

The only disadvantage is that this is now checking for valid characters in 
the string after the property has already been set, so it cannot prevent the 
setting of bad characters. But it still prints out an error message later, 
so I hope that is also still acceptable.

Let me know what you think about it!

 Thanks,
  Thomas