[libvirt] [PATCH] virt-host-validate: warn if kvm_hv is not loaded for POWER hosts

[Daniel Henrique Barboza]

On 12/17/19 2:58 PM, Cole Robinson wrote:
> On 12/12/19 4:11 PM, Daniel Henrique Barboza wrote:
>> POWER hosts does not implement CPU virtualization extensions like
>> x86 or s390x. Instead, all bare-metal POWER hosts are considered
>> to be virtualization ready.
>>
>> For POWER, the validation is done by checking the virtualization
>> kernel modules, kvm_hv and kvm_pr, to see if they are either not
>> installed or not loaded in the host. If the KVM modules aren't
>> present, we should not just warn but fail to validate.
>>
>> This patch implements this support. If kvm_hv is not installed,
>> which can be determined by 'modinfo' returning not-zero return
>> code, fail the verification. If kvm_hv is installed but not
>> loaded, show a warning. The exception are POWER8 hosts, which can
>> work with kvm_pr. In its case, ACK the use of kvm_pr if kvm_hv
>> is not loaded/present.
> 
> For x86, we check for /dev/kvm being available and usable. This side
> steps whether kvm is a module or not, in theory it could be compiled
> into the kernel. Is there anything in /dev we can check for power8?

I don't know. I'll investigate.

> 
> I don't follow the reasoning for for why the module is installed vs
> loaded matters for FAIL vs WARN. Can you expand on that a bit more?

The reasoning is that the module not present (i.e. not compiled
in the kernel) is not easy to solve, while the module not loaded is
a matter of loading either kvm_pr or kvm_hv.

The nonexistence of both kvm_pr and kvm_hv is something I haven't seen
in the field and I'm somewhat theorizing about it. I wouldn't oppose to
simply check for the modules being loaded and use WARN.


> 
> Rather than parsing /proc/modinfo, can we check for /sys/module/$modname
> instead, or something under that directory?


Just checked. If the existence of say /sys/module/kvm_hv is an indication
that the module kvm_hv is loaded, then I see no issues with checking for
this instead of parsing modinfo.




Thanks,


DHB

> 
> - Cole
>