On Sun, 2018-10-28 at 20:11 +0800, Simon Guo wrote: > Hi, > > I am using network device pass through mode with qemu x86(-device > vfio-pci,host=0000:xx:yy.z) > and “intel_iommu=on” in host kernel command line, and it shows the > whole guest memory > were pinned(vfio_pin_pages()), viewed by the “top” RES memory output. > I understand it is due > to device can DMA to any guest memory address and it cannot be > swapped. > > However can we just pin a rang of address space allowed by iommu on > that device, > instead of pin whole address space? I do notice some code like > vtd_host_dma_iommu(). > Maybe there is already some way to enable that? > > Sorry if I missed some basics. I googled some but no luck to find the > answer yet. Please > let me know if any discussion already raised on that. > > Any other suggestion will also be appreciated. For example, can we > modify the guest network > card driver to allocate only from a specific memory region(zone), and > qemu advises guest > kernel to only pin that memory region(zone) accordingly? > > Thanks, > - Simon >
I agree that it would be very convenient to be able to memory-balloon a VM with passthrough devices. All I could find was this presentation from August 2011 which talks about PPR: https://www.linux-kvm.org/images/b/b1/2011-forum-amd-iommuv2-kvm.pdf "Get rid of guest memory pinning when all assigned devices support PPR – DMA may be a bit slower on memory overcommit – But: removes a major disadvantage of direct device assignment" It looks like it might be possible for some combinations of CPU and PCI devices, sometime in the future? hope this helps, Arjen _______________________________________________ vfio-users mailing list vfio-users@redhat.com https://www.redhat.com/mailman/listinfo/vfio-users
