On Tue, Aug 30, 2016 at 09:31:27AM +0200, Cornelia Huck wrote:
> On Tue, 30 Aug 2016 11:06:50 +0800
> Jason Wang <jasow...@redhat.com> wrote:
>
> > Currently, all virtio devices bypass IOMMU completely. This is because
> > address_space_memory is assumed and used during DMA emulation. This
> > patch converts the virtio core API to use DMA API. This idea is
> >
> > - introducing a new transport specific helper to query the dma address
> > space. (only pci version is implemented).
> > - query and use this address space during virtio device guest memory
> > accessing when iommu platform (VIRTIO_F_IOMMU_PLATFORM) was enabled
> > for this device.
> >
> > Cc: Michael S. Tsirkin <m...@redhat.com>
> > Cc: Stefan Hajnoczi <stefa...@redhat.com>
> > Cc: Kevin Wolf <kw...@redhat.com>
> > Cc: Amit Shah <amit.s...@redhat.com>
> > Cc: Paolo Bonzini <pbonz...@redhat.com>
> > Cc: qemu-bl...@nongnu.org
> > Signed-off-by: Jason Wang <jasow...@redhat.com>
> > ---
> > hw/block/virtio-blk.c | 2 +-
> > hw/char/virtio-serial-bus.c | 3 +-
> > hw/scsi/virtio-scsi.c | 4 ++-
> > hw/virtio/virtio-pci.c | 14 +++++++++
> > hw/virtio/virtio.c | 62
> > ++++++++++++++++++++++++---------------
> > include/hw/virtio/virtio-access.h | 43 ++++++++++++++++++++-------
> > include/hw/virtio/virtio-bus.h | 1 +
> > include/hw/virtio/virtio.h | 8 +++--
> > 8 files changed, 98 insertions(+), 39 deletions(-)
> >
>
> > diff --git a/include/hw/virtio/virtio-access.h
> > b/include/hw/virtio/virtio-access.h
> > index 440b455..4071dad 100644
> > --- a/include/hw/virtio/virtio-access.h
> > +++ b/include/hw/virtio/virtio-access.h
> > @@ -17,12 +17,25 @@
> > #define QEMU_VIRTIO_ACCESS_H
> >
> > #include "hw/virtio/virtio.h"
> > +#include "hw/virtio/virtio-bus.h"
> > #include "exec/address-spaces.h"
> >
> > #if defined(TARGET_PPC64) || defined(TARGET_ARM)
> > #define LEGACY_VIRTIO_IS_BIENDIAN 1
> > #endif
> >
> > +static inline AddressSpace *virtio_get_dma_as(VirtIODevice *vdev)
> > +{
> > + BusState *qbus = qdev_get_parent_bus(DEVICE(vdev));
> > + VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
> > +
> > + if (virtio_host_has_feature(vdev, VIRTIO_F_IOMMU_PLATFORM) &&
> > + k->get_dma_as) {
> > + return k->get_dma_as(qbus->parent);
> > + }
> > + return &address_space_memory;
> > +}
>
> One thing I'm a bit worried about is that we're introducing a check
> even if we know that the device will never support
> VIRTIO_F_IOMMU_PLATFORM (i.e. virtio-ccw). The qom incantations will
> add cycles to any invocation of this.
Yes - let's do container_of calls as opposed to QOM on data path.
> Is the address space likely to change during device lifetime? Can we
> cache it in some way?
