[RFC PATCH 10/12] KVM: vfio_dmabuf: Fetch VFIO specific dma-buf data for sanity check

[Xu Yilun <yilun.xu@xxxxxxxxxxxxxxx>]

Fetch VFIO specific dma-buf data to see if the dma-buf is eligible to
be assigned to CoCo VM as private MMIO.

KVM expects host unaccessible dma-buf for private MMIO mapping. So need
the exporter provide this information. VFIO also provides the
struct kvm *kvm handler for KVM to check if the owner device of the
MMIO region is already assigned to the same CoCo VM.

Signed-off-by: Xu Yilun <yilun.xu@xxxxxxxxxxxxxxx>
---
 virt/kvm/vfio_dmabuf.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/virt/kvm/vfio_dmabuf.c b/virt/kvm/vfio_dmabuf.c
index c427ab39c68a..26e01b815ebf 100644
--- a/virt/kvm/vfio_dmabuf.c
+++ b/virt/kvm/vfio_dmabuf.c
@@ -12,6 +12,22 @@ struct kvm_vfio_dmabuf {
 	struct kvm_memory_slot *slot;
 };
 
+static struct vfio_dma_buf_data *kvm_vfio_dma_buf_get_data(struct dma_buf *dmabuf)
+{
+	struct vfio_dma_buf_data *(*fn)(struct dma_buf *dmabuf);
+	struct vfio_dma_buf_data *ret;
+
+	fn = symbol_get(vfio_dma_buf_get_data);
+	if (!fn)
+		return ERR_PTR(-ENOENT);
+
+	ret = fn(dmabuf);
+
+	symbol_put(vfio_dma_buf_get_data);
+
+	return ret;
+}
+
 static void kv_dmabuf_move_notify(struct dma_buf_attachment *attach)
 {
 	struct kvm_vfio_dmabuf *kv_dmabuf = attach->importer_priv;
@@ -48,6 +64,7 @@ int kvm_vfio_dmabuf_bind(struct kvm *kvm, struct kvm_memory_slot *slot,
 	size_t size = slot->npages << PAGE_SHIFT;
 	struct dma_buf_attachment *attach;
 	struct kvm_vfio_dmabuf *kv_dmabuf;
+	struct vfio_dma_buf_data *data;
 	struct dma_buf *dmabuf;
 	int ret;
 
@@ -60,6 +77,15 @@ int kvm_vfio_dmabuf_bind(struct kvm *kvm, struct kvm_memory_slot *slot,
 		goto err_dmabuf;
 	}
 
+	data = kvm_vfio_dma_buf_get_data(dmabuf);
+	if (IS_ERR(data))
+		goto err_dmabuf;
+
+	if (!data->is_private || data->kvm != kvm) {
+		ret = -EINVAL;
+		goto err_dmabuf;
+	}
+
 	kv_dmabuf = kzalloc(sizeof(*kv_dmabuf), GFP_KERNEL);
 	if (!kv_dmabuf) {
 		ret = -ENOMEM;
-- 
2.25.1