On 18/10/17 18:33, Benjamin Herrenschmidt wrote: > On Mon, 2017-10-16 at 22:11 +1100, Alexey Kardashevskiy wrote: >> On 16/10/17 19:38, Benjamin Herrenschmidt wrote: >>> On Mon, 2017-10-16 at 18:36 +1100, Alexey Kardashevskiy wrote: >>>> >>>> 1. Allow msix mapping to the userspace (to address non-64k-aligned msix bar) >>>> >>>> 2. Allow write combining in vfio for the userspace (kvm guest is kinda >>>> special and may simply ignore mapping flags in some configs but PPC radix >>>> guests still rely on this) >>> >>> Why ? The "G" bit is entirely under control of the guest afaik. >> >> Yes, for hash guests. I am not sure sure about radix, Paul pointed me to >> the code in KVM which uses the VFIO's mapping VMA. > > With radix, the HW will honor the G bit set in the guest page tables. I am sure that you know better, Paul just pointed me to this: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/powerpc/kvm/book3s_64_mmu_radix.c?h=v4.13#n403 > >> >>> This >>> would only affect qemu itself. It's still useful for things like dpdk >>> using vfio. >> >> Correct, this is useful regardless KVM. >> >>>> 3. what callback and where needs to be added to inform HV/PR KVM about VFIO >>>> group, like IOMMUMR::add_vfio_group() proposal or something. >>> >>> Can you elaborate a bit ? I haven't followed this. >> >> David knows :) >> >> >> -- Alexey
