Subject: Re: Right location in sysfs for dlpar file

From: Nathan Fontenot <[email-masked]>
Date: Mon, 01 Dec 2014 09:41:03 -0600

On 11/26/2014 09:12 PM, Benjamin Herrenschmidt wrote:
> Hi Greg,
> 
> So Nathan is working on a patch series to cleanup and improve our
> "DLPAR" infrastructure which is basically our hotplug mechanism when
> running under the PowerVM (aka pHyp) and KVM hypervisors.

The cleanup to the dlpar infrastructure will move the entire operation
of hotplugging a device to the kernel instead of doing it partially in
userspace and partially in the kernel as is currently done.

> 
> I'll let Nathan give you a bit more details/background and answer
> subsequent question you might have as this is really his area of
> expertise.
> 
> To cut a long story short, we need a sysfs file that allows our
> userspace tools to notify the kernel of hotplug events coming from
> the management console (which talks to userspace daemons using a
> proprietary protocol) to "initiate" the hotplug operations, which in
> turn get dispatched internally in the kernel to the right subsystem
> (memory, cpu, pci, ...) based on the resource type.
> 
> On IRC, Greg suggested /sys/firmware and /sys/hypervisor which both
> look like a reasonable option to me, probably better than dlpar...

For PowerVM systems we need this sysfs file to deliver what is
essentially a binary blob (specifically a rtas error log) to the
kernel. The current patch set is creating /sys/kernel/dlpar. As Ben
mentioned we would like your input on what would be the proper place
to create this file.

-Nathan