Quality-of-Service Feature Side Channels

Summary

Researchers have reported to AMD possible side channel attack methods against guest VMs in a Secure Encrypted Virtualization – Secure Nested Paging (SEV-SNP) environment by leveraging quality-of-service (QoS) extensions.

In their paper, the researchers demonstrate methods by which a malicious hypervisor might executing a side channel attack against SEV-SNP guest VMs using one of the following platform features: Cache Allocation Technology (CAT), Cache QoS Monitoring (CMT), Memory Bandwidth Allocation (MBA) Memory Bandwidth Monitoring (MBM) and Code and Data Prioritization (CDP).

AMD believes all side-channel techniques discussed in the paper fall within the category of out-of-scope behaviors according to the published SEV-SNP threat model.  AMD SEV-SNP: Strengthening VM Isolation with Integrity Protection and More

AMD recommends software developers employ existing best practices, including constant-time algorithms, and avoiding secret-dependent data accesses where appropriate.  AMD CPU Timing and Power Side-Channel Guidance

Acknowledgement 

AMD thanks the following researchers for reporting this issue and engaging in coordinated vulnerability disclosure.

Sudheendra Raghav Neela of Graz University of Technology
Carina Fiedler of Graz University of Technology
Ruiyi Zhang of CISPA Helmholtz Center for Information Security
Robin Leander Schröder of Fraunhofer SIT, Germany and Fraunhofer Austria, Austria
Michael Schwarz of CISPA Helmholtz Center for Information Security
Daniel Gruss of Graz University of Technology 

DISCLAIMER

The information contained herein is for informational purposes only and is subject to change without notice. While every precaution has been taken in the preparation of this document, it may contain technical inaccuracies, omissions and typographical errors, and AMD is under no obligation to update or otherwise correct this information. Advanced Micro Devices, Inc. makes no representations or warranties with respect to the accuracy or completeness of the contents of this document, and assumes no liability of any kind, including the implied warranties of noninfringement, merchantability or fitness for particular purposes, with respect to the operation or use of AMD hardware, software or other products described herein. Any computer system has risks of security vulnerabilities that cannot be completely prevented or mitigated. No license, including implied or arising by estoppel, to any intellectual property rights is granted by this document. Terms and limitations applicable to the purchase or use of AMD’s products are as set forth in a signed agreement between the parties or in AMD's Standard Terms and Conditions of Sale.

AMD, the AMD Arrow logo, and combinations thereof are trademarks of Advanced Micro Devices, Inc. CVE and the CVE logo are registered trademarks of The MITRE Corporation. Other product names used in this publication are for identification purposes only and may be trademarks of their respective companies.

Third party content may be licensed to you directly by the third party that owns the content and is not licensed to you by AMD. ALL LINKED THIRD-PARTY CONTENT IS PROVIDED ‘AS IS’ WITHOUT A WARRANTY OF ANY KIND. USE OF SUCH THIRD-PARTY CONTENT IS DONE AT YOUR SOLE DISCRETION AND UNDER NO CIRCUMSTANCES WILL AMD BE LIABLE TO YOU FOR ANY THIRD PARTY CONTENT. YOU ASSUME ALL RISK AND ARE SOLELY RESPONSIBILITY FOR ANY DAMAGES THAT MAY ARISE FROM YOUR USE OF THIRD-PARTY CONTENT.

© 2026 Advanced Micro Devices, Inc. All rights reserved.