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TuxCare BlogThe Cost of Hardware-Level Security Mitigations (Again)
by Joao Correia
October 30, 2024 - Technical Evangelist
In recent years, the steady influx of hardware-level vulnerabilities, like Heartbleed, Spectre, Rowhammer, and a host of others, has put every CPU vendor under scrutiny. No chip family or architecture – whether Intel, AMD, or ARM – has proven immune to these exploits.
The Linux kernel development team has responded with impressive speed and dedication, patching vulnerabilities and offering workarounds. However, the cost of these mitigations often takes a toll on performance.
It’s been a bit over a year since we discussed this topic in our blog. You can check out the previous article here, as it’s still relevant – but the story is far from over.
Mitigations: A Double-Edged Sword
While patches safeguard systems from devastating vulnerabilities, the performance hit is often unavoidable. For instance, speculative execution vulnerabilities like Meltdown and Spectre led to CPU performance reductions of up to 30% in some cases, depending on workload and architecture.
Mitigations like disabling hyper-threading, additional memory fencing, or increased overhead for memory access have been implemented, but they degrade CPU performance so significantly that users may find their top-tier, cutting-edge CPUs performing at levels comparable to older-generation hardware.
The frustration for end-users and developers alike has been mounting. Even Linus Torvalds has expressed significant frustration with the state of hardware bugs. In his recent remarks, he lamented the increasing burden of compensating for vendors’ flawed implementations. This time, his remarks were aimed at proposed patches for protecting memory copy operations – which could, theoretically, be exploitable. He has previously gone off script about AMD’s fTPM, a hardware-based Trusted Platform Module, which has faced performance issues and bugs. Users experience stuttering, causing disruptions in daily activities and rendering expensive hardware upgrades worthless. There’s a series of other situations where the Kernel team has stepped up to solve hardware level problems, and this time Linus seems to be taking a different approach – let hardware companies fix their own messes (i.e., create better products).
In a way, it’s understandable – when your Linux system suddenly loses performance, you’re just as likely to blame the OS as you are the hardware, when the OS in fact has no problem. But it’s also important to consider that hardware-level bugs are not always solvable by a microcode update. Some problems come from poor architecture decisions that won’t be reversible until 3 or 4 years down the line. And, in the meantime, your systems are at risk. Or are they? Another pet peeve mentioned in his rant is that most such vulnerabilities have never fully materialized into production-grade exploits and remain purely theoretical exercises. But the impact of the mitigations is oh so very real.
The Reality of Modern CPU Vulnerabilities
Hardware security exploits have evolved from affecting a few to impacting virtually all modern CPUs. Vulnerabilities such as Spectre, Meltdown, Foreshadow, and Lazy FPU demonstrate how deep the issues run. Modern CPUs’ intricate designs often result in vulnerabilities that are not just hard to patch but, when addressed, lead to noticeable performance degradation.
The table below illustrates the performance impact of common CPU vulnerabilities and the mitigations applied across different vendors:
| Vulnerability | Affected CPUs | Performance Impact | Mitigation | Performance Loss (Approx.) |
| Spectre/Meltdown | Intel Core, AMD Ryzen | Severe | Microcode updates | 10%-30% (varies by workload) |
| Lazy FPU | Intel x86 processors | Moderate | Microcode updates | 5%-10% |
| Foreshadow | Intel Core | High | Disabling features | Up to 30% |
| Rowhammer | DDR memory | Severe | ECC, software fixes | Minimal in some cases, noticeable in others |
| Heartbleed | Multiple architectures | Negligible (CPU) | Patching libraries | Negligible |
A Future of Compromise?
The performance drop resulting from CPU vulnerability mitigations leads to an unpleasant realization: upgrading to the latest hardware generation might not be worth it if the real-world performance advantage gets erased by necessary security patches. Many users, especially those who require consistent performance – like gamers, media professionals, or server operators – find their expensive hardware hindered by security fixes they cannot avoid.
The balance between security and performance is becoming more precarious. Until vendors can produce architectures resistant to these sophisticated attacks, end-users are forced into a compromise – security at the cost of performance. In the meantime, it seems the Linux community, under Torvalds’ leadership, will continue to fight the good fight in a world of “stupid hardware.”
Hardware vulnerabilities continue to emerge, and while kernel developers like the Linux team work tirelessly to mitigate them, the price is performance. For anyone investing in the latest hardware with hopes of gaining a significant performance boost, the reality is sobering. Until CPU vendors can address these hardware-level flaws, upgrading your system may not be as rewarding as it once was.
