Re: [libvirt] [PATCH v1 1/1] qemu_process.c: add CAP_IPC_LOCK when using libcap-ng
On 2/6/19 1:51 PM, Erik Skultety wrote:
On Wed, Feb 06, 2019 at 01:44:53PM -0200, Daniel Henrique Barboza
wrote:
> QEMU virtual machines with PCI passthrough of certain devices,
> such as the NVIDIA Tesla V100 GPU, requires allocation of an
> amount of memory pages that can break KVM limits. When that
Wow, ^this means only 1 thing, this Tesla card requires more than 1GB extra
memory to be locked, is that right?
Yes. Just checked in the dmesg of the guest out of curiosity. The very
fist big
DMA call (the one that causes the IPC_LOCK issue) is a bit larger than that
already.
There are a few nuances to be considered. As I mentioned earlier in Alex's
reply, this is a custom QEMU that has NVLink2 passthrough support. The
V100 card has 16GB of RAM that is allocated in its own NUMA node, and the
pseries machine emulates this behavior. So I am not sure if these DMAs are
locking regular host RAM or the GPU memory to populate the NUMA node
the guest uses.
If the latter, then a case can be made about allowing QEMU running with
IPC_LOCK - even if we limit it to the pseries machine assigning a Tesla
V100 device (although Yuval reported a similar issue with a Mellanox mlx5
card replied in the previous thread ...).
Thanks,
DHB
Erik