On 2026/07/24 7:29, ConKite wrote:
This patch series implements a memory isolation mode in vhost-user. The
purpose of this mode is to provide the option of additional security by
eliminating direct access of guest memory by vhost-user devices.
At a high level this works by:
1. Adding qdev and qapi properties required to enable isolation mode for
various devices.
2. Allocating an isolation memory region in an anonymous file and mapping it
to host memory. This isolation region will hold the bounce buffers and
vrings necessary to move data.
3. Using a vhost-iova-tree to allocate and track the mapping between
guest regions and their corresponding bounce buffers in the isolation
memory.
4. Creating shadow virtqueues to intercept request notifications. As
kick and call events are received by an svq, it copies buffer
contents and descriptors between isolation and guest memory before
notifying the backend or guest.
Note: This project is currently in a partially functional state. For
example, in testing vhost-user-input and a keyboard, keystrokes may
register correctly or be double counted depending on the combination
of backend daemon and guest OS used. However, the desire is to make
this work public at this stage for comment on the overall
approach.
I guess this intends to achieve something similar to IOMMU and also
Linux's swiotlb for the VMM (please correct me if I'm wrong):
> Other edge case scenarios arise for bounce buffers. For example, when
> IOMMU mappings are set up for a DMA operation to/from a device that is
> considered “untrusted”, the device should be given access only to the
> memory containing the data being transferred. But if that memory
> occupies only part of an IOMMU granule, other parts of the granule may
> contain unrelated kernel data. Since IOMMU access control is
> per-granule, the untrusted device can gain access to the unrelated
> kernel data. This problem is solved by bounce buffering the DMA
> operation and ensuring that unused portions of the bounce buffers do
> not contain any unrelated kernel data.
https://docs.kernel.org/next/core-api/swiotlb.html#usage-scenarios
It would be nice if the security property this feature provides is
explicitly stated, ideally as documentation.
I also hope this could fix vhost-user for TCG:
https://gitlab.com/qemu-project/qemu/-/work_items/2092
Perhaps the memory isolation should be enabled by default for TCG.
Implementation-wise, there are rough edges as you stated. Some of them
can be fixed by more closely following what vhost-user does for the
non-isolated case and what vhost-vdpa does with shadow virtqueues.
Regards,
Akihiko Odaki
Signed-off-by: Connor Kite <[email protected]>
---
ConKite (2):
vhost-user: Consolidate chardev property definitions
vhost-user: Add memory-isolation qdev property to vhost-user devices
Connor Kite (13):
backends/cryptodev-vhost-user: add memory isolation bool
net/vhost-user: add memory isolation
vhost-user: add memory_isolation to VhostUserState
util/iova-tree: g_tree_foreach wrapper
hw/virtio: iova_tree_foreach wrapper
hw/virtio/vhost-shadow-virtqueue: used handler
hw/virtio/vhost-shadow-virtqueue: specified vring placement
hw/virtio/vhost-shadow-virtqueue: range boundary in translation
hw/virtio/vhost-user: create isolation region
hw/virtio/vhost-user: send isolation regions to device
hw/virtio/vhost-user: add shadow virtqueues and eventfd intercepts
hw/virtio/vhost-user: handle data movement with shadow vqs
hw/virtio/vhost-user: shadow vq cleanup
backends/cryptodev-vhost-user.c | 24 +-
backends/vhost-user.c | 4 +-
hw/block/vhost-user-blk.c | 4 +-
hw/display/vhost-user-gpu.c | 4 +-
hw/scsi/vhost-user-scsi.c | 4 +-
hw/virtio/vhost-iova-tree.c | 15 ++
hw/virtio/vhost-iova-tree.h | 3 +
hw/virtio/vhost-shadow-virtqueue.c | 30 ++-
hw/virtio/vhost-shadow-virtqueue.h | 17 ++
hw/virtio/vhost-stub.c | 3 +-
hw/virtio/vhost-user-base.c | 13 +-
hw/virtio/vhost-user-fs.c | 4 +-
hw/virtio/vhost-user-gpio.c | 4 -
hw/virtio/vhost-user-i2c.c | 5 -
hw/virtio/vhost-user-input.c | 5 -
hw/virtio/vhost-user-rng.c | 5 -
hw/virtio/vhost-user-rtc.c | 4 -
hw/virtio/vhost-user-scmi.c | 4 +-
hw/virtio/vhost-user-snd.c | 1 -
hw/virtio/vhost-user-spi.c | 5 -
hw/virtio/vhost-user-test-device.c | 1 -
hw/virtio/vhost-user-vsock.c | 4 +-
hw/virtio/vhost-user.c | 441 ++++++++++++++++++++++++++++++++++-
include/hw/virtio/vhost-user-base.h | 1 +
include/hw/virtio/vhost-user-blk.h | 1 +
include/hw/virtio/vhost-user-fs.h | 1 +
include/hw/virtio/vhost-user-scmi.h | 1 +
include/hw/virtio/vhost-user-vsock.h | 1 +
include/hw/virtio/vhost-user.h | 6 +-
include/hw/virtio/virtio-gpu.h | 1 +
include/hw/virtio/virtio-scsi.h | 1 +
include/qemu/iova-tree.h | 13 ++
include/system/vhost-user-backend.h | 3 +-
net/passt.c | 16 +-
net/vhost-user.c | 11 +-
qapi/net.json | 15 +-
qapi/qom.json | 6 +-
util/iova-tree.c | 5 +
38 files changed, 622 insertions(+), 64 deletions(-)
---
base-commit: 006a22cb26998998385b104db1ff9466ef2f3153
change-id: 20260604-vhost-user-isolated-memory-070ed4833ee7
Best regards,
