On Fri, Oct 11, 2019 at 06:25:19PM -0700, Ram Pai wrote: > From: Thiago Jung Bauermann <bauer...@linux.ibm.com> > > Normally, virtio enables DMA API with VIRTIO_F_IOMMU_PLATFORM, which must > be set by both device and guest driver. However, as a hack, when DMA API > returns physical addresses, guest driver can use the DMA API; even though > device does not set VIRTIO_F_IOMMU_PLATFORM and just uses physical > addresses. > > Doing this works-around POWER secure guests for which only the bounce > buffer is accessible to the device, but which don't set > VIRTIO_F_IOMMU_PLATFORM due to a set of hypervisor and architectural bugs. > To guard against platform changes, breaking any of these assumptions down > the road, we check at probe time and fail if that's not the case. > > cc: Benjamin Herrenschmidt <b...@kernel.crashing.org> > cc: David Gibson <da...@gibson.dropbear.id.au> > cc: Michael Ellerman <m...@ellerman.id.au> > cc: Paul Mackerras <pau...@ozlabs.org> > cc: Michael Roth <mdr...@linux.vnet.ibm.com> > cc: Alexey Kardashevskiy <a...@linux.ibm.com> > cc: Jason Wang <jasow...@redhat.com> > cc: Christoph Hellwig <h...@lst.de> > Suggested-by: Michael S. Tsirkin <m...@redhat.com> > Signed-off-by: Ram Pai <linux...@us.ibm.com> > Signed-off-by: Thiago Jung Bauermann <bauer...@linux.ibm.com>
Reviewed-by: David Gibson <da...@gibson.dropbear.id.au>
I don't know that this is the most elegant solution possible. But
it's simple, gets the job done and pretty unlikely to cause mysterious
breakage down the road.
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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