On Wed, May 10, 2023 at 08:11:28AM +0000, Tian, Kevin wrote: > > From: Nicolin Chen <nicolinc@xxxxxxxxxx> > > Sent: Wednesday, May 10, 2023 11:33 AM > > > > One unique requirement for SMMUv3 nested translation support is the MSI > > doorbell address translation, which is a 2-stage translation too. And, > > to working with the ITS driver, an msi_cookie needs to be setup on the > > kernel-managed domain, the stage-2 domain of the nesting setup. And the > > same msi_cookie will be fetched, via > > iommu_dma_get_msi_mapping_domain(), > > in the iommu core to allocate and creates IOVA mappings for MSI doorbell > > page(s). However, with the nesting design, the device is attached to a > > user-managed domain, the stage-1 domain. So both the setup and fetching > > of the msi_cookie would not work at the level of stage-2 domain. Thus, > > on both sides, the msi_cookie setup and fetching require a redirection > > of the domain pointer. It's easy to do so in iommufd core, but needs a > > new op in the iommu core and driver. > > > > Looks the new preferred way is to map the physical ITS page to an IPA > provided by Qemu then let the guest allocate the cookie in S1 which > is then passed back by Qemu to the host kernel? [1] > > [1] https://lore.kernel.org/linux-iommu/5ff0d72b-a7b8-c8a9-60e5-396e7a1ef363@xxxxxxx/ Hmm..is that something firm to implement at this stage? Thank you Nicolin
