On Thu, Oct 11, 2012 at 11:48 PM, Avi Kivity <a...@redhat.com> wrote: > On 10/11/2012 05:34 PM, Michael S. Tsirkin wrote: >> On Thu, Oct 11, 2012 at 04:35:23PM +0200, Avi Kivity wrote: >>> On 10/11/2012 04:35 PM, Michael S. Tsirkin wrote: >>> >>> >> No, qemu should configure virtio devices to bypass the iommu, even if it >>> >> is on. >>> > >>> > Okay so there will be some API that virtio devices should call >>> > to achieve this? >>> >>> The iommu should probably call pci_device_bypasses_iommu() to check for >>> such devices. >> >> So maybe this patch should depend on the introduction of such >> an API. > > I've dropped it for now. > > In fact, virtio/vhost are safe since they use cpu_physical_memory_rw() > and the memory listener watches address_space_memory, no iommu there.
Not quite sure your meaning. My understanding is that as a pci device, vhost can lie behind a iommu in topology, which result in the transaction launched can be snapped by the emulated iommu. BUT we make a exception for vhost-dev and enforce address_space_rw(address_space_memory, ..) NOT address_space_rw(pci_dev->bus_master_as,..) for vhost device, so we bypass the iommu. Right? Regards, pingfan > vfio needs to change to listen to pci_dev->bus_master_as, and need > special handling for iommu regions (abort for now, type 2 iommu later). > > -- > error compiling committee.c: too many arguments to function
