Re: [libvirt] running Libvirt from source code, IPC_LOCK and VFIO

On Fri, Feb 01, 2019 at 07:40:36PM -0200, Daniel Henrique Barboza wrote: > Update: I've figured it out. > > The bug here was that, even running as root, I was getting errors like: > > error : virQEMUCapsNewForBinaryInternal:4687 : internal error: Failed to > probe QEMU binary with > QMP: libvirt:  error : prctl failed to enable 'dac_override' in the AMBIENT > set: > Operation not permitted > > The reason is that the host has libcap-ng installed. ./configure uses it if > available, > setting WITH_CAPNG in the code. I am unsure if this has something to do with > the libcap-ng configuration in this system I'm using or if there is > something > missing in the Libvirt code, but the spawned QEMU process isn't inheriting > the > capabilities it should have. > > Disabling support of this lib with "--with-capng=no" in autogen.sh and > rebuilding Libvirt fixed the problem. I was even able to see more NUMA > nodes than I was before using the system libvirt (which is the original > bug I am/was investigating). > > > Thanks! > Hey Daniel, I had the same problem with Mellanox RDMA device as backend for pvrdma device where the mlx5 driver also enforces CAP_IPC_LOCK. So at first i use this as a workaround but i knew that it is not a final approach as it makes a wrong use of memory. <memoryBacking> <locked/> </memoryBacking> Anyways, your tip helps so wanted to say thanks!

Yuval > > > > On 2/1/19 4:04 PM, Daniel Henrique Barboza wrote: >> Hi, >> >> I'm facing a strange behavior when running Libvirt from source code, >> latest upstream, on an Ubuntu 18.04.1 LTS Power 9 server. My QEMU >> guest - which is using VFIO and GPU passthrough - breaks on boot when >> trying to allocate a DMA window inside KVM. >> >> Debugging the code, I've found out that the problem is related to the >> process >> not having CAP_IPC_LOCK - at least from the host kernel perspective. >> >> This is strange because: >> >> - the same VM running directly from QEMU command line works >> - the same VM running in the system Libvirt (v4.0.0, Ubuntu version) >> also works >> >> What am I missing? My understanding on Linux process is that a process >> running as root should inherit the same capabilities of the user, which >> includes >> CAP_IPC_LOCK. Running Libvirt from source code should grant ipc_lock >> to it ... right? >> >> >> >> Any help is appreciated. I can provide more details (VM XML for example) >> if necessary. >> >> >> Thanks! > -- > libvir-list mailing list > libvir-list(a)redhat.com > https://www.redhat.com/mailman/listinfo/libvir-list