On 2016年08月30日 15:31, 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-block@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?
I think so, we can cache it in vdev and set it during features set. Then we can avoid qom stuffs during data path.
