> Jason Wang <jasowang@xxxxxxxxxx> hat am 23.10.2020 11:10 geschrieben: > > > On 2020/10/23 下午5:00, 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? > > > It's just because it has been implemented. In addition to implement > IOTLB, the virtio-vsock-pci must advertise ATS capability as well. > > > > 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. > > > A question, is vIOMMU a must for making SEV work? Based on the demo code from AMD where they just use "-device virtio-scsi-pci,id=scsi,disable-legacy=on,iommu_platform=true" and my understanding of IOMMU: no, I don't think so. The ATS capability is only required for vIOMMU, right? > > Thanks > > > > > >>> --- > >>> 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
