A bug that’s present in all Intel CPUs produced in the last decade requires an operating system fix that will slow down system performance.
AMD has made some real progress in its battle against Intel for CPU market share, by releasing the new Ryzen processors based on the Zen architecture in 2017. Ryzen chips already provide a compelling price-performance advantage over Intel equivalents, and that advantage could get a real boost in 2018. Apparently, all Intel CPUs produced in the last decade suffer a security flaw that can only be fixed in software, with a real performance penalty.
As The Register reports, the bug is related to related how programs access memory, specifically information that should only be accessible to the operating system kernel that maintains the highest level of privileges. Thanks to the bug, user programs can access protected the protected kernel memory space and “see” information that should be locked away.
The full details are not yet available, and in any case, they’re quite technical and relate to how a CPU moves in and out of protected kernel mode. The result is what matters: Intel processors keep the kernel in virtual memory to make that process as fast as possible. If the CPU doesn’t have to dump and then reload the kernel, then it can achieve faster performance. Unfortunately, that practice makes kernel contents vulnerable to being accessed by nefarious programs, and it’s hard-coded into Intel’s x86/x64 architecture.
The fix, therefore, has to be implemented by the operating system, in a process labeled Kernel Page Table Isolation (KPTI) that puts the kernel in an area of protected memory space that cannot be accessed by other programs. That creates extra processing steps — dumping and then reloading kernel data — that slow things down, which is estimated to be anywhere from five percent to 30 percent depending on the process.
All operating systems will need to implement some form of KPTI in order to bypass the bug and improve security. Microsoft will be implementing its own changes in an upcoming Windows 10 Patch Tuesday update, and indeed has apparently been testing things in Windows Insider builds. Linux and MacOS will also need to be updated, meaning this is an equal-opportunity bug.
For its part, AMD has indicated that its own CPUs do not suffer from this kind of bug and so won’t require any performance-sapping fixes. If you’re thinking about building or buying a new PC, then you have yet another reason to consider an AMD Ryzen solution. If you currently own a system based on a modern Intel CPU, then you’ll need to be prepared to see lesser performance once the fixes are rolled out.
