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virtio-devices: iommu: allow limiting maximum address width in bits

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Currently, Cloud Hypervisor does not set a VIRTIO_IOMMU_F_INPUT_RANGE
feature bit for the VirtIO IOMMU device, which, according to spec[1],
means that the guest may use the whole 64-bit address space is for
IOMMU purposes:

>If the feature is not offered, virtual mappings span over the whole
>64-bit address space (start = 0, end = 0xffffffff ffffffff)

As far as I am aware, there are currently no host platforms on
the market capable of addressing the whole 64-bit address space.

For example, I am currently working with a host platform that reports
39-bit address space for IOMMU purposes:

>DMAR: Host address width 39

When running a VFIO pass-through guest on such a platform, NVIDIA
driver in guest gets DMA mapping failures when working with large data,
and this results in Cloud Hypervisor exiting with the following error:

>cloud-hypervisor: 1501.220535s: <__iommu>
>ERROR:virtio-devices/src/thread_helper.rs:53 -- Error running worker:
>HandleEvent(Failed to process request queue : ExternalMapping(Custom
>{ kind: Other, error: "failed to map memory for VFIO container, iova
>0x7fff00000000, gpa 0x24ce25000, size 0x1000: IommuDmaMap(Error(22))"
>}))

Passing "--platform iommu_address_width=39" to Cloud Hypervisor built
with this change fixes this.

[1]: https://docs.oasis-open.org/virtio/virtio/v1.3/csd01/
virtio-v1.3-csd01.html#x1-5420006

Signed-off-by: Nikolay Edigaryev <edigaryev@gmail.com>
This commit is contained in:
Nikolay Edigaryev
2025-01-08 12:15:25 +04:00
committed by Rob Bradford
parent 74ca38f7a9
commit 27fda753e1
3 changed files with 22 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

11
vmm/src/device_manager.rs
View File

@@ -100,7 +100,8 @@ use crate::pci_segment::PciSegment;
use crate::serial_manager::{Error as SerialManagerError, SerialManager};
use crate::vm_config::{
ConsoleOutputMode, DeviceConfig, DiskConfig, FsConfig, NetConfig, PmemConfig, UserDeviceConfig,
VdpaConfig, VhostMode, VmConfig, VsockConfig, DEFAULT_PCI_SEGMENT_APERTURE_WEIGHT,
VdpaConfig, VhostMode, VmConfig, VsockConfig, DEFAULT_IOMMU_ADDRESS_WIDTH_BITS,
DEFAULT_PCI_SEGMENT_APERTURE_WEIGHT,
};
use crate::{device_node, GuestRegionMmap, PciDeviceInfo, DEVICE_MANAGER_SNAPSHOT_ID};
@@ -1365,6 +1366,13 @@ impl DeviceManager {
) -> DeviceManagerResult<()> {
let iommu_id = String::from(IOMMU_DEVICE_NAME);
let iommu_address_width_bits =
if let Some(ref platform) = self.config.lock().unwrap().platform {
platform.iommu_address_width_bits
} else {
DEFAULT_IOMMU_ADDRESS_WIDTH_BITS
};
let iommu_device = if self.config.lock().unwrap().iommu {
let (device, mapping) = virtio_devices::Iommu::new(
iommu_id.clone(),
@@ -1373,6 +1381,7 @@ impl DeviceManager {
.try_clone()
.map_err(DeviceManagerError::EventFd)?,
self.get_msi_iova_space(),
iommu_address_width_bits,
state_from_id(self.snapshot.as_ref(), iommu_id.as_str())
.map_err(DeviceManagerError::RestoreGetState)?,
)