On 2020-06-15 12:37, Halil Pasic wrote:
On Mon, 15 Jun 2020 11:01:55 +0800
Jason Wang <jasowang@xxxxxxxxxx> wrote:
hum, in between I found another way which seems to me much better:
We already have the force_dma_unencrypted() function available which
AFAIU is what we want for encrypted memory protection and is already
used by power and x86 SEV/SME in a way that seems AFAIU compatible
with our problem.
Even DMA and IOMMU are different things, I think they should be used
together in our case.
What do you think?
The patch would then be something like:
diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index a977e32a88f2..53476d5bbe35 100644
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c
@@ -4,6 +4,7 @@
#include <linux/virtio_config.h>
#include <linux/module.h>
#include <linux/idr.h>
+#include <linux/dma-direct.h>
#include <uapi/linux/virtio_ids.h>
/* Unique numbering for virtio devices. */
@@ -179,6 +180,10 @@ int virtio_finalize_features(struct virtio_device
*dev)
if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1))
return 0;
+ if (force_dma_unencrypted(&dev->dev) &&
+ !virtio_has_feature(dev, VIRTIO_F_IOMMU_PLATFORM))
+ return -EIO;
+
virtio_add_status(dev, VIRTIO_CONFIG_S_FEATURES_OK);
status = dev->config->get_status(dev);
if (!(status & VIRTIO_CONFIG_S_FEATURES_OK)) {
I think this can work but need to listen from Michael
I don't think Christoph Hellwig will like force_dma_unencrypted()
in virtio code:
https://lkml.org/lkml/2020/2/20/630
Regards,
Halil
OK, then back to the first idea.
Thanks,
Pierre
--
Pierre Morel
IBM Lab Boeblingen
