Re: [libvirt] [PATCH 8/8] qemu: set qemu process' RLIMIT_MEMLOCK when VFIO is used

VFIO requires all of the guest's memory and IO space to be lockable in RAM. The domain's max_balloon is the maximum amount of memory the domain can have (in KiB). We add a generous 1GiB to that for IO space (still much better than KVM device assignment, where the KVM module actually *ignores* the process limits and locks everything anyway), and convert from KiB to bytes. In the case of hotplug, we are changing the limit for the already existing qemu process (prlimit() is used under the hood), and for regular commandline additions of vfio devices, we schedule a call to setrlimit() that will happen after the qemu process is forked. --- src/qemu/qemu_command.c | 22 +++++++++++++++------- src/qemu/qemu_hotplug.c | 24 +++++++++++++++++------- 2 files changed, 32 insertions(+), 14 deletions(-) + /* VFIO requires all of the guest's memory to be + * locked resident, plus some amount for IO + * space. Alex Williamson suggested adding 1GiB for IO + * space just to be safe (some finer tuning might be + * nice, though). + */ + virCommandSetMaxMemLock(cmd, ((unsigned long long)def->mem.max_balloon + (1024 * 1024)) * 1024);

+ virSetMaxMemLock(vm->pid, + ((unsigned long long)vm->def->mem.max_balloon + (1024 * 1024)) * 1024);