> From: arjenvanweel...@gmail.com > To: vfio-users@redhat.com > Subject: Re: [vfio-users] Can VFIO pin only a specific region of guest > mem when use pass through devices? > Message-ID: <2b7384b34ff6c4f851b631bf1300b34251ece23c.ca...@gmail.com> > Content-Type: text/plain; charset="UTF-8" > > 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 Arjen,
Got it. Appreciate your help on this. Thanks, - Simon _______________________________________________ vfio-users mailing list vfio-users@redhat.com https://www.redhat.com/mailman/listinfo/vfio-users
