Daniel P. Berrangé, Sep 03, 2024 at 12:08:
On Mon, Sep 02, 2024 at 03:09:42PM +0200, Peter Krempa wrote:
On Thu, Aug 22, 2024 at 17:59:47 +0200, Anthony Harivel wrote:
Add the support in libvirt to activate the RAPL feature in QEMU. I suppose that the 'rapl-helper-socket' is a shared (multiple qemu's use it) resource set up beforehand by the admin. Right?
The qemu-pr-helper could be run as a single instnce, or it could be run per-QEMU instance. The latter would give us better security isolation, for what is a privileged daemon. On the other hand, I wonder about the CPU overhead of having 100's of copies of the process running on a host.
If it runs on a single instance, then the socket needs to be chmod/chown to something like qemu / libvirt group with access only to root and group. Running one helper instance per-QEMU instance would mean that every instance read 1 MSR / Package every second. The socket is left open (thanks to Daniel suggestion in QEMU review). The impact would be quite low I guess on the housekeeping CPU. When I designed the daemon with Paolo, the first solution was the main idea but I'm open to any solution that leads to a better adoption of the feature. Thanks, Anthony
If that is the case that means the lifecycle of the daemon and permissions (including selinux) for accessing the socket are not something that libvirt needs to deal with.
If either of them isn't true please outline how that socket is to be used to see how libvirt will need to approach it.
With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|