On Fri, Oct 23, 2020 at 11:00:54AM +0200, Sebastian Hofmann wrote: > > Michael S. Tsirkin <mst@xxxxxxxxxx> hat am 22.10.2020 13:39 geschrieben: > > > > > > On Wed, Oct 21, 2020 at 05:14:25PM +0200, Sebastian Hofmann wrote: > > > virtio_ring does not work with active memory encryption because the host cannot read it. Fix this by enforcing the use of DMA which uses shared (unencrypted) memory pages. > > > > > > Signed-off-by: Sebastian Hofmann <sebastian@xxxxxxxxxxxx> > > > > > > Sorry, no. > > host which can not access all of driver memory must set VIRTIO_F_ACCESS_PLATFORM. > > > > Not worth it to work around broken hosts. > > > > Xen is an exception we carry around since it predates the > > introduction of VIRTIO_F_ACCESS_PLATFORM. > > > > > > Thanks for pointing out VIRTIO_F_ACCESS_PLATFORM which I was not aware of. Maybe that patch was a bit naïve. > > Basically I'm looking for a way to use vsock with qemu on AMD SEV. When I try to use IOMMU for vsock I get an EOPNOTSUPP out of vhost_vsock_set_features. > > Is there a reason why vhost_vsock_set_features doesn't use vhost_init_device_iotlb as done in the net device? Because that would have been my next attempt. > I would appreciate a short comment on this idea or a recommendation for another solution that is better than the patch below. Not sure I understand the problem. Are you using qemu? If so just add iommu_platform=on and you are done. > > > --- > > > drivers/virtio/virtio_ring.c | 5 +++++ > > > 1 file changed, 5 insertions(+) > > > > > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > > > index becc77697960..8c68c475ec21 100644 > > > --- a/drivers/virtio/virtio_ring.c > > > +++ b/drivers/virtio/virtio_ring.c > > > @@ -12,6 +12,7 @@ > > > #include <linux/hrtimer.h> > > > #include <linux/dma-mapping.h> > > > #include <xen/xen.h> > > > +#include <linux/mem_encrypt.h> > > > > > > #ifdef DEBUG > > > /* For development, we want to crash whenever the ring is screwed. */ > > > @@ -255,6 +256,10 @@ static bool vring_use_dma_api(struct virtio_device *vdev) > > > if (xen_domain()) > > > return true; > > > > > > + /* Memory encryption requires DMA */ > > > + if (mem_encrypt_active()) > > > + return true; > > > + > > > return false; > > > } > > > > > > -- > > > 2.25.1 _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
