On Tue, 2014-09-02 at 16:56 -0400, Konrad Rzeszutek Wilk wrote: > On Wed, Sep 03, 2014 at 06:53:33AM +1000, Benjamin Herrenschmidt wrote: > > On Mon, 2014-09-01 at 22:55 -0700, Andy Lutomirski wrote: > > > > > > On x86, at least, I doubt that we'll ever see a physically addressed > > > PCI virtio device for which ACPI advertises an IOMMU, since any sane > > > hypervisor will just not advertise an IOMMU for the virtio device. > > > But are there arm64 or PPC guests that use virtio_pci, that have > > > IOMMUs, and that will malfunction if the virtio_pci driver ends up > > > using the IOMMU? I certainly hope not, since these systems might be > > > very hard-pressed to work right if someone plugged in a physical > > > virtio-speaking PCI device. > > > > It will definitely not work on ppc64. We always have IOMMUs on pseries, > > all PCI busses do, and because it's a paravirtualized environment, > > napping/unmapping pages means hypercalls -> expensive. > > > > But our virtio implementation bypasses it in qemu, so if virtio-pci > > starts using the DMA mapping API without changing the DMA ops under the > > hood, it will break for us. > > What is the default dma_ops that the Linux guests start with as > guests under ppc64?
On pseries (which is what we care the most about nowadays) it's dma_iommu_ops() which in turn call into the "TCE" code for populating the IOMMU entries which calls the hypervisor. Cheers, Ben. > Thanks! > > > > Cheers, > > Ben. > > > > _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization
