Hi,

we always use the standard pci busdma machinery. Therefore we should
negotiate the VIRTIO_F_ACCESS_PLATFORM feature if it is offered.
Strictly speaking we should bypass any existing iommus if the host 
does not offer this feature, but this no regression and we can do that 
when/if we introduce our own busdma tag for virtio.

Accepting VIRTIO_F_ACCESS_PLATFORM is required for SEV on KVM/qemu.

ok?

Cheers,
Stefan

diff --git a/sys/dev/pci/virtio_pci.c b/sys/dev/pci/virtio_pci.c
index f9c8801ceb7..3e6f3d69295 100644
--- a/sys/dev/pci/virtio_pci.c
+++ b/sys/dev/pci/virtio_pci.c
@@ -821,6 +821,8 @@ virtio_pci_negotiate_features_10(struct virtio_softc *vsc,
 	uint64_t host, negotiated;
 
 	vsc->sc_driver_features |= VIRTIO_F_VERSION_1;
+	/* we always use the standard pci busdma_tag */
+	vsc->sc_driver_features |= VIRTIO_F_ACCESS_PLATFORM;
 	/* notify on empty is 0.9 only */
 	vsc->sc_driver_features &= ~VIRTIO_F_NOTIFY_ON_EMPTY;
 	CWRITE(sc, device_feature_select, 0);