vfio_dma_map() is the exclusive means that QEMU uses to insert translations for an assigned device. It is not only used by AMD vIOMMU, in fact that's probably one of the less tested use vectors, it's used when QEMU establishes any sort of memory mapping for the VM. Any mapping that could possibly be a DMA target for the device should filter through the MemoryListener and result in a call to vfio_dma_map(). This includes all memory that is considered RAM by the VM, as well as possibly direct mapped peer-to-peer DMA ranges. When the device is backed by an IOMMU, vfio_dma_map() will pin pages to establish a fixed IOMMU translation. vfio_pin_pages() comes into play when the device we're assigning is not backed by the IOMMU, which can be the case with a mediated device (mdev). Interactions with these devices are mediated by a vendor driver in the host kernel where the vendor driver provides device isolation and translation by acting as an interposer between the user and the device. The vfio_pin_pages() interface allows the vendor driver in the host kernel to request page pinning such that the mapping is fixed while DMA is performed by the physical backing device. Thanks,
Alex
_______________________________________________ vfio-users mailing list vfio-users@redhat.com https://www.redhat.com/mailman/listinfo/vfio-users
