On Tue, 6 Dec 2016 18:59:14 +0800 Peter Xu <pet...@redhat.com> wrote:
> On Tue, Dec 06, 2016 at 04:27:39PM +0800, Lan Tianyu wrote: > > [...] > > > > > > >> User space driver(E.G DPDK) also can enable/disable > > >> IOVA for device dynamically. > > > > > > Could you provide more detailed (or any pointer) on how to do that? I > > > did try to find it myself, I see an VFIO_IOMMU_ENABLE ioctl, but looks > > > like it is for ppc only. > > > > No, I just give an example that user space may do that but no more > > research. But since Qemu already can enable device's IOVA, other user > > application also should can do that with the same VFIO interface, right? > > AFAIU we can't do that at least on x86. We can use vfio interface to > bind group into container, but we should not be able to dynamically > disable IOMMU protection. IIUC That needs to taint the kernel. > > The only way I know is that we probe vfio-pci with no-iommu mode, in > that case, we disabled IOMMU, but we can never dynamically enable it > as well. > > Please correct me if I am wrong. A vfio user such as QEMU enabling or disabling translation in the vIOMMU is "simply" assigning the vfio container to the system AddressSpace (as we do w/o vIOMMU) or the device specific, IOMMU domain, AddressSpace. The device must be protected by the pIOMMU domain (container) at all times. Thanks, Alex
