Intel® Data Streaming Accelerator – Unable to Turn On SVA

An Error Message appears when enabling Intel® DSA (Data Streaming Accelerator).

Behavior: When executing the command dmesg | grep -i idxd

Error Message: Unable to turn on SVA feature

Intel® DSA (Data Streaming Accelerator) depends on a series of drivers present on the OS distribution to be able to function properly. As described on Intel® Data Streaming Accelerator User Guide page 15, Intel® DSA (Data Streaming Accelerator) was tested on the following OS’s:

Visit the vendor website for more information about distributions and embedded Kernel* drivers on a specific distribution.

To identify the issue's root cause, we need to analyze the information from Intel® DSA (Data Streaming Accelerator) and Linux commands together, looking for inconsistencies or missing elements related to VT-d and PRICtl functionalities, as follows:

VT-d Status:

One of the requirements for Intel® DSA (Data Streaming Accelerator) is the option VT-D enabled on the BIOS.

1. Verify that VT-D is enabled on the BIOS.
2. Execute the commands below. If the output is similar to the example below means VT-d reserved DMAR (Direct Memory Access Remapping) table memory and VT-d is enabled.

dmesg -t | grep ACPI | grep DMAR

BIOS Enabled Options

On the BIOS settings, please make sure the following options are correct:

enabled Opt-Out Illegal MSI Mitigation

enabled PRS Capability for PCIe

disabled Limit CPU PA to 46 bits

Driver Status

To check the driver status on the OS, execute the following commands:

journalctl | grep 'Kernel command line'

Look if the kernel parameters for Intel® DSA are loaded on the bootloader:

Kernel Boot Parameters:

To check if the kernel parameters are loaded, execute the following:

RedHat and Ubuntu Distributions

cat /proc/cmdline

The output will show the intel_iommu=on,sm_on included on the Kernel*.

Ubuntu Distributions

grep -i vtd /etc/default/grub

and

grep -i vtx /etc/default/grub

Check for if the options listed below are set to off. That might disable VT-d functionalities.

If so, turn options to on

like intel_vtd.active=off

intel_vtd_cmt_mode=off
 

How to check if Intel® DSA (Data Streaming Accelerator) is enabled on the OS distribution

Run: dmesg -t | grep "idxd"

The output should be like the following:

Note: When running dmesg -t | grep "idxd"  if you see Unable to turn on SVA feature, VT-d scalable mode may not be enabled by default on the kernel and bootloader.

Solution: Include the parameters intel_iommu=on,sm_on into the kernel and bootloader to enable VT-d scalable mode.

Linux Kernel and Bootloader Parameters

Depending on your Linux OS distribution the process to add a new parameter on the Kernel e/or Bootloader will be different. Consult with your Linux* OS vendor for more details.

To check if the parameters are included on the bootloader, run:

cat /proc/cmdline

How to include parameters on the Kerner/bootloader:

Note: The following example is based on a RedHat* 9 distribution:

1. Access the system as a sudo user;
2. Edit the Bootloader:

   nano /boot/loader/entries/edbb445aff2d4cf79085273ad1b8b6bf-6.9.4-1.el9.elrepo.x86_64.conf

3. Execute grubby update
4. Reboot the system
5. Check if SVA is enabled: dmesg -t | grep "idxd"

   

For Ubuntu* Distributions:

1. Add this grub config command in /etc/default/grub file:
2. GRUB_CMDLINE_LINUX_DEFAULT="intel_iommu=on,sm_on iommu=on"
3. Run update-grub
4. Reboot the system.

For complete details, review the Intel® Data Streaming Accelerator User Guide.