Re: [Qemu-devel] [PATCH qemu v14 16/18] spapr_iommu, vfio, memory: Notify IOMMU about starting/stopping being used by VFIO

[David Gibson]

On Tue, Mar 22, 2016 at 05:24:33PM +1100, Alexey Kardashevskiy wrote:
> On 03/22/2016 03:45 PM, David Gibson wrote:
> >On Mon, Mar 21, 2016 at 06:47:04PM +1100, Alexey Kardashevskiy wrote:
> >>The sPAPR TCE tables manage 2 copies when VFIO is using an IOMMU -
> >>a guest view of the table and a hardware TCE table. If there is no VFIO
> >>presense in the address space, then just the guest view is used, if
> >>this is the case, it is allocated in the KVM. However since there is no
> >>support yet for VFIO in KVM TCE hypercalls, when we start using VFIO,
> >>we need to move the guest view from KVM to the userspace; and we need
> >>to do this for every IOMMU on a bus with VFIO devices.
> >>
> >>This adds vfio_start/vfio_stop callbacks in MemoryRegionIOMMUOps to
> >>notifiy IOMMU about changing environment so it can reallocate the table
> >>to/from KVM or (when available) hook the IOMMU groups with the logical
> >>bus (LIOBN) in the KVM.
> >>
> >>This removes explicit spapr_tce_set_need_vfio() call from PCI hotplug
> >>path as the new callbacks do this better - they notify IOMMU at
> >>the exact moment when the configuration is changed, and this also
> >>includes the case of PCI hot unplug.
> >>
> >>TODO: split into 2 or 3 patches, per maintainership area.
> >>
> >>Signed-off-by: Alexey Kardashevskiy <address@hidden>
> >
> >I'm finding this one much easier to follow than the previous revision.
> >
> >>---
> >>  hw/ppc/spapr_iommu.c  | 12 ++++++++++++
> >>  hw/ppc/spapr_pci.c    |  6 ------
> >>  hw/vfio/common.c      |  9 +++++++++
> >>  include/exec/memory.h |  4 ++++
> >>  4 files changed, 25 insertions(+), 6 deletions(-)
> >>
> >>diff --git a/hw/ppc/spapr_iommu.c b/hw/ppc/spapr_iommu.c
> >>index 6dc3c45..702075d 100644
> >>--- a/hw/ppc/spapr_iommu.c
> >>+++ b/hw/ppc/spapr_iommu.c
> >>@@ -151,6 +151,16 @@ static uint64_t spapr_tce_get_page_sizes(MemoryRegion 
> >>*iommu)
> >>      return 1ULL << tcet->page_shift;
> >>  }
> >>
> >>+static void spapr_tce_vfio_start(MemoryRegion *iommu)
> >>+{
> >>+    spapr_tce_set_need_vfio(container_of(iommu, sPAPRTCETable, iommu), 
> >>true);
> >>+}
> >>+
> >>+static void spapr_tce_vfio_stop(MemoryRegion *iommu)
> >>+{
> >>+    spapr_tce_set_need_vfio(container_of(iommu, sPAPRTCETable, iommu), 
> >>false);
> >>+}
> >
> >Wonder if a single callback which takes a boolean might be a little
> >less clunky.
> 
> I have a feeling that at least once I was asked to do the opposite and now
> we have take_ownership/release_ownership. This does not seem to be much
> different and the existing names are more self-documenting than the previous
> vfio_notify() or whatever name I could think of.

Ok, leave it as is.

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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