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.
Is the address space likely to change during device lifetime? Can we
cache it in some way?
