On 10/15/2018 03:17 PM, Daniel P. Berrangé wrote:
On Mon, Oct 15, 2018 at 02:39:26PM +0200, Michal Privoznik wrote:
https://bugzilla.redhat.com/show_bug.cgi?id=1633562
Under <memoryBacking/> we allow users to configure various memory backing related knobs. However, there are some combinations that make no sense. For instance, requesting hugepages and file allocation at the same time. Forbid this configuration then.
The huge pages we allocate come from a file in /dev/hugepages, so this description doesn't really make sense.
Sure, in the end the mmap() that qemu calls is a file somewhere under /dev/hugepages (btw terrible, really terrible path for hugetlbfs mount point because it suggests hugepages are devices). But <source type='file'/> is usually used to put domain RAM under /var/lib/libvirt/ram/.. (and to enforce memory-backing-file).
IIUC, what's actually happening is that you're trying to avoid a historical bug.
More or less. This basically a result of 992bf863fcc. Anyway, might as well do nothing on this front :-) Michal