Introduce a new PCIIOMMUOps optional callback, get_viommu_cap() which
allows to retrieve capabilities exposed by a vIOMMU. The first planned
vIOMMU device capability is VIOMMU_CAP_HW_NESTED that advertises the
support of HW nested stage translation scheme. pci_device_get_viommu_cap
is a wrapper that can be called on a PCI device potentially protected by
a vIOMMU.
get_viommu_cap() is designed to return 64bit bitmap of purely emulated
capabilities which are only determined by user's configuration, no host
capabilities involved. Reasons are:
1. host may has heterogeneous IOMMUs, each with different capabilities
2. this is migration friendly, return value is consistent between source
and target.
3. host IOMMU capabilities are passed to vIOMMU through set_iommu_device()
interface which have to be after attach_device(), when get_viommu_cap()
is called in attach_device(), there is no way for vIOMMU to get host
IOMMU capabilities yet, so only emulated capabilities can be returned.
See below sequence:
vfio_device_attach():
iommufd_cdev_attach():
pci_device_get_viommu_cap() for HW nesting cap
create a nesting parent hwpt
attach device to the hwpt
vfio_device_hiod_create_and_realize() creating hiod
...
pci_device_set_iommu_device(hiod)
Suggested-by: Yi Liu <[email protected]>
Signed-off-by: Zhenzhong Duan <[email protected]>
---
MAINTAINERS | 1 +
include/hw/iommu.h | 19 +++++++++++++++++++
include/hw/pci/pci.h | 25 +++++++++++++++++++++++++
hw/pci/pci.c | 11 +++++++++++
4 files changed, 56 insertions(+)
create mode 100644 include/hw/iommu.h
diff --git a/MAINTAINERS b/MAINTAINERS
index a07086ed76..54fb878128 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2305,6 +2305,7 @@ F: include/system/iommufd.h
F: backends/host_iommu_device.c
F: include/system/host_iommu_device.h
F: include/qemu/chardev_open.h
+F: include/hw/iommu.h
F: util/chardev_open.c
F: docs/devel/vfio-iommufd.rst
diff --git a/include/hw/iommu.h b/include/hw/iommu.h
new file mode 100644
index 0000000000..7dd0c11b16
--- /dev/null
+++ b/include/hw/iommu.h
@@ -0,0 +1,19 @@
+/*
+ * General vIOMMU capabilities, flags, etc
+ *
+ * Copyright (C) 2025 Intel Corporation.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#ifndef HW_IOMMU_H
+#define HW_IOMMU_H
+
+#include "qemu/bitops.h"
+
+enum {
+ /* hardware nested stage-1 page table support */
+ VIOMMU_CAP_HW_NESTED = BIT_ULL(0),
+};
+
+#endif /* HW_IOMMU_H */
diff --git a/include/hw/pci/pci.h b/include/hw/pci/pci.h
index 6b7d3ac8a3..cde7a54a69 100644
--- a/include/hw/pci/pci.h
+++ b/include/hw/pci/pci.h
@@ -462,6 +462,21 @@ typedef struct PCIIOMMUOps {
* @devfn: device and function number of the PCI device.
*/
void (*unset_iommu_device)(PCIBus *bus, void *opaque, int devfn);
+ /**
+ * @get_viommu_cap: get vIOMMU capabilities
+ *
+ * Optional callback, if not implemented, then vIOMMU doesn't
+ * support exposing capabilities to other subsystem, e.g., VFIO.
+ * vIOMMU can choose which capabilities to expose.
+ *
+ * @opaque: the data passed to pci_setup_iommu().
+ *
+ * Returns: 64bit bitmap with each bit represents a capability emulated by
+ * VIOMMU_CAP_* in include/hw/iommu.h, these capabilities are theoretical
+ * which are only determined by vIOMMU device properties and independent
+ * on the actual host capabilities they may depend on.
+ */
+ uint64_t (*get_viommu_cap)(void *opaque);
/**
* @get_iotlb_info: get properties required to initialize a device IOTLB.
*
@@ -642,6 +657,16 @@ bool pci_device_set_iommu_device(PCIDevice *dev,
HostIOMMUDevice *hiod,
Error **errp);
void pci_device_unset_iommu_device(PCIDevice *dev);
+/**
+ * pci_device_get_viommu_cap: get vIOMMU capabilities.
+ *
+ * Returns a 64bit bitmap with each bit represents a vIOMMU exposed
+ * capability, 0 if vIOMMU doesn't support exposing capabilities.
+ *
+ * @dev: PCI device pointer.
+ */
+uint64_t pci_device_get_viommu_cap(PCIDevice *dev);
+
/**
* pci_iommu_get_iotlb_info: get properties required to initialize a
* device IOTLB.
diff --git a/hw/pci/pci.c b/hw/pci/pci.c
index c70b5ceeba..df1fb615a8 100644
--- a/hw/pci/pci.c
+++ b/hw/pci/pci.c
@@ -2992,6 +2992,17 @@ void pci_device_unset_iommu_device(PCIDevice *dev)
}
}
+uint64_t pci_device_get_viommu_cap(PCIDevice *dev)
+{
+ PCIBus *iommu_bus;
+
+ pci_device_get_iommu_bus_devfn(dev, &iommu_bus, NULL, NULL);
+ if (iommu_bus && iommu_bus->iommu_ops->get_viommu_cap) {
+ return iommu_bus->iommu_ops->get_viommu_cap(iommu_bus->iommu_opaque);
+ }
+ return 0;
+}
+
int pci_pri_request_page(PCIDevice *dev, uint32_t pasid, bool priv_req,
bool exec_req, hwaddr addr, bool lpig,
uint16_t prgi, bool is_read, bool is_write)
--
2.47.1
