kvm: defer huge page recovery vhost task to later

Some libraries want to ensure they are single threaded before forking,
so making the kernel's kvm huge page recovery process a vhost task of
the user process breaks those. The minijail library used by crosvm is
one such affected application.

Defer the task to after the first VM_RUN call, which occurs after the
parent process has forked all its jailed processes. This needs to happen
only once for the kvm instance, so introduce some general-purpose
infrastructure for that, too.  It's similar in concept to pthread_once;
except it is actually usable, because the callback takes a parameter.

Cc: Sean Christopherson <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Tested-by: Alyssa Ross <[email protected]>
Signed-off-by: Keith Busch <[email protected]>
Message-ID: <[email protected]>
[Move call_once API to include/linux. - Paolo]
Cc: [email protected]
Fixes: d96c77bd4eeb ("KVM: x86: switch hugepage recovery thread to vhost_task")
Signed-off-by: Paolo Bonzini <[email protected]>

0 files changed, 0 insertions, 0 deletions