Re: [libvirt] [PATCH] qemu: process: Fix automatic setting of locked memory limit for VFIO

On Fri, 2015-11-06 at 08:30 +0100, Peter Krempa wrote:

Now the next question is whether this peer-to-peer DMA is useful, or even used. I have heard of users assigning multiple AMD cards to a system and making use of AMD's XDMA crossfire support, which certainly seems like it's using this capability. NVIDIA may follow along, but they seem to limit SLI in their driver. But as I said, these aren't counting against the locked memory limit and there's probably very little potential use of peer-to-peer between assigned and emulated devices. At the time I first implemented VFIO, I couldn't see a way to tell the difference between mappings for emulated and assigned devices, they're all just opaque mappings. However, I think we could now be a bit smarter to figure out the device associated with the MemorySection and skip emulated device regions. If we were to do that, we could expose it as a new option to vfio-pci, so libvirt could probe for it and

maybe remove the fudge factor on the lock limit. Thanks,