On Tue, Feb 17, 2015 at 01:36:38PM +1100, Alexey Kardashevskiy wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > On 02/05/2015 03:49 PM, David Gibson wrote: > > On Thu, Jan 29, 2015 at 08:27:30PM +1100, Alexey Kardashevskiy wrote: > >> TCE hypercalls (H_PUT_TCE, H_PUT_TCE_INDIRECT, H_STUFF_TCE) use a > >> logical bus number (LIOBN) to identify which TCE table the request > >> is addressed to. However VFIO kernel driver operates with IOMMU > >> group IDs and has no idea about which LIOBN corresponds to which > >> group. If the host kernel supports in-kernel acceleration for TCE > >> calls, we have to provide the LIOBN to IOMMU mapping information. > >> > >> This makes use of a VFIO KVM device's > >> KVM_DEV_VFIO_GROUP_SET_SPAPR_TCE_LIOBN attribute to set the link > >> between LIOBN and IOMMU group. > >> > >> The vfio_container_spapr_set_liobn() helper is implemented > >> completely in vfio.c because kvm_vfio_spapr_tce_liobn needs a group > >> fd and we do not want to share resources likes that outside vfio.c. > > > > I thought you'd moved away from the idea of in-kernel TCE > > acceleration, since big DMA windows made it unnecessary. > > > Not entirely. DDW may not be supported by some hardware (like nVidia > being able to generate only 40bit DMA addresses without hacks). DMA > memory registering is pretty much about it - when we preregister pages, > the KVM acceleration becomes lot simpler as it does not have to take care > of pinning or locked_vm accounting.
Ok, that makes sense.
> But I should have not posted it here anyway, too early :)
> >> Signed-off-by: Alexey Kardashevskiy <a...@ozlabs.ru> ---
> >> hw/ppc/spapr_iommu.c | 1 + hw/ppc/spapr_pci_vfio.c | 11
> >> +++++++++++ hw/vfio/common.c | 33
> >> +++++++++++++++++++++++++++++++++ include/hw/vfio/vfio.h | 4 ++++
> >> 4 files changed, 49 insertions(+)
> >>
> >> diff --git a/hw/ppc/spapr_iommu.c b/hw/ppc/spapr_iommu.c index
> >> 258f837..3de95d7 100644 --- a/hw/ppc/spapr_iommu.c +++
> >> b/hw/ppc/spapr_iommu.c @@ -142,6 +142,7 @@ static int
> >> spapr_tce_table_realize(DeviceState *dev) if (!tcet->table) { size_t
> >> table_size = tcet->nb_table * sizeof(uint64_t); tcet->table =
> >> g_malloc0(table_size); + tcet->vfio_accel = false;
> >
> > This should probably have a qdev prop so that it can be explicitly
> > disabled on a per-device basis for testing.
>
>
> It is a TCE table's property, how can you disable it if it is not created
> via the command line?
Uh, yeah it would have to be a property on VIO devices and on VFIO
host bridges which the propagates the option to the TCE table.
Hrm, that does sound a bit messy now I think about it.
--
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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