Re: [libvirt] [PATCH] qemu: Drop qemuDomainMemoryLimit

On Fri, Aug 09, 2013 at 07:13:58AM -0600, Eric Blake wrote: > On 08/09/2013 06:56 AM, Michal Privoznik wrote: >> This function is to guess the correct limit for maximal memory >> usage by qemu for given domain. This can never be guessed >> correctly, not to mention all the pains and sleepless nights this >> code has caused. Once somebody discovers algorithm to solve the >> Halting Problem, we can compute the limit algorithmically. But >> till then, this code should never see the light of the release >> again. >> --- >> src/qemu/qemu_cgroup.c | 3 +-- >> src/qemu/qemu_command.c | 2 +- >> src/qemu/qemu_domain.c | 49 ------------------------------------------------- >> src/qemu/qemu_domain.h | 2 -- >> src/qemu/qemu_hotplug.c | 2 +- >> 5 files changed, 3 insertions(+), 55 deletions(-) > > ACK. Users that put an explicit limit in their XML are taking on their > own risk at guessing correctly; all other users should not be forced to > suffer from a bad guess on our part killing their domain. If we don't understand how to calculate a default limit that works, how are users with even less knowledge than us, suppose to calculate an explicit level of their own ? This limit was designed so that the hosts are not vulnerable to DOS attack from a compromised QEMU, so removing this is arguably introducing a security weakness in our default deployment. I think I'd like to see some feedback / agreement from QEMU developers that this problem really can't be solved, before we remove it. Daniel