[libvirt] [PATCH] qemu: Refresh capabilities when creating resctrl allocation

[Peter Krempa]

On Fri, Feb 02, 2018 at 12:44:03 +0100, Martin Kletzander wrote:
> Since one of the things in capabilities (info from resctrl updated with data
> about caches) can be change on the system by remounting the /sys/fs/resctrl with
> different options, the capabilities need to be refreshed.  There is a better fix
> in the works, but it's going to be way bigger than this (hence the XXX note
> there), so for the time being let's workaround this.  And in order not to slow
> down the domain starting, only get the capabilities if there are any cachetunes.
> 
> Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1540780

This BZ describes a crash if the filesystem is remounted, but you are
attempting to fix this not by fixing the code that crashed but by
re-loading the information if possibly somebody remounted it.

This does not seem to be the correct fix since you still have a race
window, where the options can be changed after the refresh is executed
and prior to using them in the code where it actually crashed.
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