Re: [PATCH] tools: fix xen-detect to correctly identify domU type

[David Vrabel <david.vrabel@citrix.com>]

On 23/03/16 11:12, Andrew Cooper wrote:
> On 23/03/16 10:59, David Vrabel wrote:
>> On 23/03/16 10:55, Andrew Cooper wrote:
>>> On 23/03/16 10:52, Juergen Gross wrote:
>>>> On 23/03/16 11:32, David Vrabel wrote:
>>>>> On 23/03/16 10:25, Jan Beulich wrote:
>>>>>>>>> On 23.03.16 at 11:14, <JGross@suse.com> wrote:
>>>>>>> 7. Report type according to features found (this is a little bit
>>>>>>>    ugly: we have to rely on the current hypervisor implementation
>>>>>>>    regarding the bits set for the different guest types).
>>>>>> Well, in some of the cases feature flags only make sense for one
>>>>>> kind of guest, so if such a flag is set it could be used as positive
>>>>>> indication (while it being clear may then still mean nothing).
>>>>>>
>>>>>>> Would it make sense to add another file to /sys/hypervisor/properties?
>>>>>>> Something like guest_type, containing "pv", "hvm" or "pvh"? If existing
>>>>>>> this could be used to report the guest type.
>>>>>> That would seem a good idea to me. What do others, namely
>>>>>> Linux maintainers, think?
>>>>> What's the use case for user space knowing if it's in a PV or HVM domain?
>>>> The first thing coming to my mind would be diagnostic tools.
>>> Having the admin able to tell for informational purposes is useful. 

This is useful because...?

>>> They can find out by looking at the top of `dmesg`, but a hypervisor
>>> sysfs node is cleaner than requiring the admin to know every printk()
>>> variant that Xen puts out.
>>>
>>> That is it however.  It specifically shouldn't be used for any other
>>> decisions, as it isn't relevant.
>> I think it should be the toolstack that presents this information.
>>
>> I don't think we should add a new kernel ABI for this.
> 
> A toolstack is not present in a domU.

So?  The guest admin doesn't need to be in the guest itself to get this
information -- it's right there is the xl configuration for the guest.

David

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