On 08/12/2021, 16:21:29, Nathan Lynch wrote: > Laurent Dufour <lduf...@linux.ibm.com> writes: >> On 07/12/2021, 18:07:50, Nathan Lynch wrote: >>> Laurent Dufour <lduf...@linux.ibm.com> writes: >>>> On 07/12/2021, 15:32:39, Nathan Lynch wrote: >>>>> Is there a reasonable fallback for VMs where this parameter doesn't >>>>> exist? PowerVM partitions should always have it, but what do we want the >>>>> behavior to be on other hypervisors? >>>> >>>> In that case, there is no value displayed in the /proc/powerpc/lparcfg and >>>> the lparstat -i command will fall back to the device tree value. I can't >>>> see any valid reason to report the value defined in the device tree >>>> here. >>> >>> Here's a valid reason :-) >>> >>> lparstat isn't the only possible consumer of the interface, and the >>> 'ibm,partition-name' property and the dynamic system parameter clearly >>> serve a common purpose. 'ibm,partition-name' is provided by qemu. >> >> If the hypervisor is not providing this value, this is not the goal of this >> interface to fetch it from the device tree. >> >> Any consumer should be able to fall back on the device tree value, and >> there is no added value to do such a trick in the kernel when it can be >> done in the user space. > > There is value in imposing a level of abstraction so that the semantics > are: > > * Report the name assigned to the guest by the hosting environment, if > available > > as opposed to > > * Return the string returned by a RTAS call to ibm,get-system-parameter > with token 55, if implemented > > The benefit is that consumers of lparcfg do not have to be coded with > the knowledge that "if a partition_name= line is absent, the > ibm,get-system-parameter RTAS call must have failed, so now I should > read /sys/firmware/devicetree/base/ibm,partition_name." That's the sort > of esoterica that is appropriate for the kernel to encapsulate. > > And I'd say the effort involved (falling back to a root node property > lookup) is proportional to the benefit. >
I don't agree. >From the kernel point of view, I can't see any benefit, this is adding more complexity to do in the kernel what can be done easily in user space. This is typically what should be implemented in a user space shared library.
