Btw, IOMMUv2 can support peripheral page request (PPR) so in theory if an end point pcie device can support ATS/PRI, pinning down all memory is not necessary, does current vfio driver or qemu has corresponding support to save pinned memory? thanks.
On Sun, Jul 12, 2020 at 11:03 AM Yv Lin <yvl...@gmail.com> wrote: > Hi Alex, > thanks for the detailed explanation. it does clarify more to me. I read > the vfio_listener_region_add() more carefully. It seems check every > memory region against container's host window, for IOMMUv1 vfio device, the > host window is always 64bit full range （vfio_host_win_add(container, 0, > (hwaddr)-1, info.iova_pgsizes); in vfio_connect_container()）, so basically > mean all memory region will be pinned and mapped to host IOMMU, is the > understanding right? > > thanks. > > On Sun, Jul 12, 2020 at 6:49 AM Alex Williamson < > alex.l.william...@gmail.com> wrote: > >> 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 >> >
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