Re: [libvirt] [PATCH] qemuBuildCommandLine: Fall back to mem balloon if there's no hard_limit

If there's no hard_limit set and domain uses VFIO we still must lock the guest memory (prerequisite from qemu). Hence, we should compute the

amount to be locked from max_baloon.

--- src/qemu/qemu_command.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c index c8f7df2..71c220f 100644 --- a/src/qemu/qemu_command.c +++ b/src/qemu/qemu_command.c @@ -9219,8 +9219,19 @@ qemuBuildCommandLine(virConnectPtr conn, goto error; } - if (mlock) - virCommandSetMaxMemLock(cmd, def->mem.hard_limit * 1024); + if (mlock) { + unsigned long long memKB; + + /* 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). + */ + memKB = def->mem.hard_limit ? + def->mem.hard_limit : def->mem.max_balloon + 1024 * 1024; + virCommandSetMaxMemLock(cmd, memKB * 1024); + }